Effects of toughened matrix resins on composite materials for wind turbine blades
by Ricardo Orozco
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Chemical Engineering
Montana State University
© Copyright by Ricardo Orozco (1999)
Abstract:
Different resins with a potential for use in wind turbine blades have been studied. The main
consideration in the resin selection has been to increase the structural integrity such as delamination
resistance in blades while maintaining or improving other mechanical properties. A second concern
was to increase the temperature and moisture -resistance relative to the baseline orthophtalic polyester
resin. The resins included in the study are also appropriate for the wind turbine blade application in
terms of cost and have a sufficiently low viscosity to allow processing by resin transfer molding.
Resins included unsaturated polyesters, vinylesters, epoxies, and a urethane. Neat resin properties
evaluated include stress-strain and heat deflection temperature. Composite properties evaluated include
Modes I and II delamination resistance (GIC and GIIC), transverse tension of [0/±45/0]s, [0]6 and
[±45]3 laminates, O° compression of [0/±45/0]s laminates and skin-stiffened substructural tests.
Moisture effects on neat resins, [0/±45/0]s and [0]6 laminates have been briefly explored. Composite
properties are also compared relative to resin cost, and processing observations are given for each resin.
The results are presented relative to those for the baseline low cost unsaturated orthophthalic polyester
resin system. Significant improvements are shown for some vinyl ester and epoxy resins in terms of
delamination resistance, structural integrity, transverse strength, and moisture and temperature
resistance. While some of the tougher resins show significantly lower resin modulus, heat resistance,
and laminate compressive strength, several of the resins perform as well as the baseline system in terms
of these properties. Composite property dependence on neat resin properties is generally consistent
with theoretical expectations. The best performing vinyl esters cost moderately more than the baseline
polyester, while the best epoxies are significantly more costly; the epoxies are also more difficult to
process. 
EFFECTS OF TOUGHENED MATRIX RESINS ON COMPOSITE MATERIALS
FOR WIND TURBINE BLADES
by
Ricardo Orozco
A thesis submitted in partial fulfillment 
of the requirements for the degree
of
Master of Science 
in
Chemical Engineering
MONTANA STATE UNIVERSITY-BOZEMAN » 
Bozeman, Montana
July 1999
e < ^
ii
APPROVAL 
of a thesis submitted by 
Ricardo Orozco
This thesis has been read by each member of the thesis committee and has been 
found to be satisfactory regarding content, English usage, format, citations, bibliographic 
style and consistency, and is ready for submission to the College of Graduate Studies.
Dr. John Mandell / I / / - C P / 4
x Chairperson, Graduate Committee
( 7
Date
Approved for the Department of Chemical Engineering 
Dr. John Sears / V --?/ ^
/^Department Head Date
Approved for the College of Graduate Studies 
Dr. Bruce R. McLeod — y-zz-f?
Graduate Dean./ Date
iii
STATEMENT OF PERMISSION TO USE 
In presenting this thesis in partial fulfillment of the requirements for a master's 
degree at Montana State University-Bozeman, I agree that the Library shall make it 
available to borrowers under rules of the Library.
IfI have indicated my intention to copyright this thesis by including a copyright 
notice page, copying is allowable only for scholarly purposes, consistent with "fair use" 
as prescribed in the U.S. Copyright Law. Requests for permission for extended quotation 
from or reproduction of this thesis in whole or in parts may be granted only by the
copyright holder.
Signature _ 
Date
V
ACKNOWLEDGMENTS
I would like to thank Dr. John Mandell for his continuous assistance, guidance 
and encouragement that enable me to achieve my academic goal. I would like to thank 
Dr. Douglas Caims for his direction and insight. Thanks are directed to Dr. Bonnie Tyler 
for serving as a graduate committee member. I thank Daniel Samborsky for his advice 
and assistance with manufacturing specimens, experimental testing, data analysis and 
computer skills. Tb the composite group for their support, advice, and the good 
moments. I specially thank my family for their endless love and support.
Finally, I would like to thank Sandia National Laboratories for supporting this 
research and the wind turbine energy project.
VTABLE OF CONTENTS
LIST OF TABLES vii
LIST OF FIGURES 
ABSTRACT.............
I. INTRODUCTION
2. BACKGROUND...................................
Polymer Matrix Selection ...............
Polymer Overview..........................
Properties of Polymers....................
Thermal Properties..............
Tension and Compression....
Polymer Chemistry.........................
Polyester Resins...................
Vinyl Ester Resins...............
Epoxy Resins......................
Polyurethane Resins............
Resin Toughness in the Composite.. 
DCB and ENF test Methods 
Skin Stiffener Structure.... .
3
3
.10 
.14 
. 14 
. 16 
. 17 
. 18 
.21 
:. 22
,23
3. EXPERIMENTAL METHODS.................... ........
Polymer Resin Systems................... ................
Test Methods...................................... .............
Delamination Tests.............................
Skin Stiffener Test..............................
Heat Deflection Temperature..............
Manufacturing Process........................ ...........-
Specimen Preparation and Testing Equipment 
Test for DCB and ENF Specimens...... ...........
25
25
27
27
30
31
33
34 
37'
4. RESULTS AND DISCUSSION..................
Introduction............................................
Neat Resin Properties............. ................
Tensile Stress-Strain Curves......
Heat Deflection Temperature.....
Composite Properties.............................
Interlaminar Fracture Toughness 
Polyester Resins...............
39
39
39
39
41 
42,
42
43
VO 
ON Q
\
Vinyl Ester Resins................................
Epoxy Resins..................................... .
Polyurethane Resin.......... ....................
Overall Toughness Comparison...........
Blended Resins................. ...................
Effects of Fabric Architecture on Gic ...
Results for T-Stiffener Specimens.................
Transverse Strength........................ ..............
Compressive Strength....,.......................
Toughness vs. Other Mechanical Properties.. 
Moisture Effects on Mechanical Properties...
Water Absorption..........................................
Resin Pricing and Overall Comparisons...................
Resin Pricing................ ..... .......................—
Overall Comparisons............. ......................
Processing Observations................. .........................
5. CONCLUSIONS AND RECOMENDATIONS.............
Conclusion................................................................
Recommendations.................... ..............-.............. * ■ ■
REFERENCES CITED.........................................................
vi
44
45
47
47
49
50
51
56
62
64
66
69
71
71
,72
,75
.77
..77
„81
„83
APPENDIX 
Individual Test Results 86
LIST OF TABLES
Table Pa§e
2.1 Preferred resin characteristics............... .................................................................. 5
3.1 Catalyst, promoters and curing conditions for vinyl ester resins............................ 26
3.2 Mix ratios and cure conditions for epoxy resins..................................................... 27
3.3 Layups, fiber volumes and thickness for different tests.......................................... 34
3.4 Ply configuration and average thickness for skin-stiffener specimens.................... 35
3.5 Dimensions for tensile, compressive and water absorption specimens..................35
3.6 Test rates for different tests......... i................. .............................-...........................36
3.7 Geometry and lay-ups for DCB specimens using UC1018ZV fabrics............... ......38
4.1 Tensile test results for neat resin.............................................. ........................ - -
4.2 Heat deflection temperatures for different resins...............   42
4.3 Gic and Gnc for polyester resins.............................................................................. 44
4.4 Gic and Gnc for vinyl ester resins............................................................................ 45
4.5 Gic and Gnc for epoxy resins................................................................................... 46
4.6 Gic and Gnc for polyurethane resin......... :............................... ..............................47
4.7 Comparison of GIC and E modulus for different Swancorp
resins and blend............ ................................. ........................ ......................,.......
4.8 Results for T-Stiffener Pull off Tests...................................................................... 52
4.9 Tensile results for [0/±45/0]s composite using different resins.................... ......... 57
4.10 Tensile results for [0/+45/0]s composite using Derkahe ^
vinyl ester resins........................................................................................ ..........
4.11 Results for [0/±45/0]s composite using different resins......................................... 62
4.12 Results for [0/±45/0]s using Derakane vinyl ester resins........ ..............................63
4.13 Water absorption (% weight gain) for neat resin and 
composite specimens...............................................
viii
LIST OF FIGURES
Figure
2.1 Laminate stress-strain curve............................................................ ..............
2.2 Knee stress at 0.2 % strain................................................ ............................
2.3 Unsaturated polyester...................................... ................................. .............
2.4 Bysphenol A vinyl ester................................................................................
2.5 Typical epoxy and epoxy reaction.............................................. ...... -.....
2.6 Polyurethane reaction...... .............. .........................;.............. ......................
2.7 Composite interlaminar strain energy release rates for steady crack growth
as a function of the neat resin GIC for different resin systems....................
2.8 Geometry and loading for a DCB specimen.................. ..............................
2.9 Loading and approximate dimensions for skin-stiffener T-specimens.... .
2.10 Typical load-displacement curve for a skin-stiffener specimen..................
3.1 Geometry and loading for ENF....................................................................
3.2 Load-displacement plot for a DCB test.......................................................
3.3 Schematic of heat deflection t e s t ........ ................................................. —
3 .4 Displacement-temperature curve for a HDT test....................... ..................
3.5 DCB and ENF specimens............................................................................
3.6 Test fixture used for ENF and T-Specimens................................ ...............
3.7 Different fabrics used............................................................ ......................
4.1 Stress-strain curves for tensile tests of neat resins.......................................
4.2 Modes I and II for toughened resins............................................................
4.3 Comparison of Gic test (b) results for different resin systems.....................
Page 
....13.
....14
....19
....20
.....20
.....21
.....22
...............23
. . : , 4
..... 24
...............29
...............29
...............32
.................33 -
.............36
......37
.................38
...... 40
...... 46
.......48
4.4 Comparison of Gnc results for different resin systems..........................
4.5 Comparison of Gic test (b) values using different resin systems...........
4.6 Load-displacement curves for T-Specimens.................................... ......
4.7 Derakane 804 and System 41 !-Specimens............. ..............................
4.8 Epoxy SC-14 T-Specimen.....................................................................
4.9 Comparison between maximum load for stiffener pull off tests
and One......................................... ................. .....................................
4.10 Stress-strain diagram for [0/+45/0]s composite with different resms....
4.11 Tension specimens tested in the 90° direction................... ...................
4.12 Experimental vs. predicted 90° Modulus for [0]6 composite................
4.13 Modulus E, for neat resin and composites tested at 90° in tension.......
4.14 Knee stress for neat resin and composites tested at 90° in tension..... .
4.15 Experimental values for [0/±45/0]s versus predicted compressive
strength for the 0° layers alone..........................................................-
4.16 90° Modulus vs. Gic for [0/±45/0]s composite.................................... .
4.17 0° Compressive strength vs. Gic for [0/+45/0]s composite.................
4.18 90° Modulus for wet and dry [0/+45/0]s composite tested
at room temperature............................................................................
4.19 90° Tensile strength for wet and dry [0/+45/0]s composite tested
at room temperature .................................. .................. ................—•
4.20 0° Compressive strength for wet and dry [0/+45/0]s composite tested
at room temperature................................................................. ...........
4.21 90° Knee stress for wet and dry [0/+45/0]s composite tested
at room temperature...................................................... ......................
4.22 Resin prices for a 40,000 lbs estimation.....................................’•........
51
52
54
55
56 
,58 
.59 
.60 
.61 
.61
.64
.65
.65
..67
..68
..68
..69
48
...71
xi
4.23 Comparison between polyester resins studied and the CoRezyn 63-AX-051
4.24 Comparison between vinyl ester resins studied and the
CoRezyn 63-AX-051 ....................... -...........................................................
4.25 Comparison between epoxy resins studied and the
CoRezyn 63-AX-051 ...................... ......... ...................................................
4.26 Comparison between urethane resin studied and the
CoRezyn 63-AX-051 ...................................................................................
ABSTRACT
Different resins with a potential for use in wind turbine blades have been studied. 
The main consideration in the resin selection has been to increase the structural integrity 
such as delamination resistance in blades while maintaining or improving other 
mechanical properties. A second concern was to increase the temperature and moisture 
resistance relative to the baseline orthophtalic polyester resin. The resins included m the 
study are also appropriate for the wind turbine blade application in terms of cost and have 
a sufficiently low viscosity to allow processing by resin transfer molding. Resins 
included unsaturated polyesters, vinylesters, epoxies, and a urethane. Neat resin 
properties evaluated include stress-strain and heat deflection temperature. Composite 
properties evaluated include Modes I and II delamination resistance (Gtc and Gbc), 
transverse tension of [0/±45/0]s, [0]6 and [±45]3 laminates, O0 compression of [0/+45/0]s 
laminates and skin-stiffened substructural tests. Moisture effects on neat resins,
[0/±45/0]s and [0]e laminates have been briefly explored. Composite properties are also 
compared relative to resin cost, and processing observations are given for each resin.
The results are presented relative to those for the baseline low cost unsaturated 
orthophthalic polyester resin system. Significant improvements are shown for some vinyl 
ester and epoxy resins in terms of delamination resistance, structural integrity, transverse 
strength and moisture and temperature resistance. While some of the tougher resins show 
significantly lower resin modulus, heat resistance, and laminate compressive strength, 
several of the resins perform as well as the baseline system in terms of these properties. 
Composite property dependence on neat resin properties is generally consistent with 
theoretical expectations. The best performing vinyl esters cost moderately more than the 
baseline polyester, while the best epoxies are significantly more costly; the epoxies are 
also more difficult to process.
ICHAPTER I 
INTRODUCTION
This thesis presents the results of a study of matrix resins for use in wind turbine 
blades constructed from glass fiber reinforced plastic composite materials. Wind turbines 
must perform for 20 to 30 years in a variety of climates. The cost of the blades is a major 
component to the cost of wind generated energy. The blade materials consist of fibrous 
glass reinforcement fabrics with a polymer resin matrix as the continuous phase, 
surrounding each fiber. While many manufacturing methods are available for composite 
materials, most blades use either hand lay-up or resin transfer molding. (RTM). This , 
limits the type of resin to thermosets, which have a sufficiently low viscosity for these 
manufacturing methods. A database has been developed at MSU [1] using a common 
orthophthalic polyester resin matrix for most of the materials. The purpose of this study 
was to seek resins which would provide improved structural integrity (primarily 
delamination resistance) while maintaining other properties similar to the baseline 
polyester resin. Improved temperature and moisture resistance and reasonable cost were 
major objectives.
The approach taken was to select several potential resins which were suitable for 
RTM manufacturing (thermosets with low viscosity). The resins included polyesters, 
epoxies, vinyl esters and a urethane. Of these, the first three classes of resins are currently
2used in wind turbine blade manufacture, and the urethanes are an extreme case of high 
toughness. Composite laminates with a common glass fabric reinforcement and ply 
configuration including plies with fibers oriented at O0 and +45° were prepared by RTM 
and machined into test specimens. The mechanical tests chosen for evaluation are of 
importance in blade performance and are also sensitive to the matrix. Tests included the
following: compressive loading parallel to the main reinforcing fibers (0°), tension
,
perpendicular to the main reinforcing fibers (90°) and at +45°, interlaminar fracture 
toughness (Gic and Gnc), and neat resin tension. Performance in a typical substructure 
geometry, a T-stiffener section, was also evaluated.
A major concern driving test selection was that, as resins are modified to increase 
toughness, stiffness (elastic modulus) tends to decrease, which has led to decreases in 
compression strength in other studies [2], Softening of the matrix at elevated 
temperatures and high moisture contents tends to exacerbate this problem.
The various resins included in this study are thought to represent a meaningful selection 
of relatively low cost resins suitable for RTM processing, which could reasonably be 
expected to perform well under typical wind turbine blade use conditions.
CHAPTER 2
BACKGROUND 
Polymer Matrix Selection
The Matrix of a composite works as a binder transferring the loads through the 
fiber network. It maintains the fiber orientation and protects the fibers from 
environmental effects, redistributing the load to surrounding fibers when and individual 
fiber breaks. Important considerations when selecting a resin candidate are the stiffness 
(elastic modulus) and the yield and ultimate strength and toughness properties. Other 
factors such as thermal properties, processability, cost, availability, and health concerns 
are also of a great importance [3].
The resin must be compatible with the processing method. Resin transfer molding, 
(RTM) is the main process of concern in this study. This process involves a two-part 
mold, with a fiber preform placed into the mold and the mold then closed. The resin is 
then pumped under low pressure through injection ports into the mold, filling the mold 
and completely wetting out the reinforcement; Both the mold and resin can be heated 
depending on the type of resin. Currently, the aerospace industry is a major user of RTM 
components, and the automotive industry has made limited use of RTM for decades [4]. 
Infrastructure, sports and military are industries where RTM is also gaining, popularity.
/
4The advantages of RTM relative to hand layup are improved quality, higher production 
rates, reduced labor, and lower volatiles emissions; the main disadvantages are higher 
equipment costs and the need for low viscosity resins.
The application of composite materials to primary structure to reduce structural 
weight is forcing structural designers and materials engineers to look for new, toughened 
resin systems. Thermosets, elastomers, and thermoplastics are the three main polymer 
categories. Thermoset polymers dominate as matrices in structural composite applications 
for reasons of good mechanical and thermal properties, good bonding to reinforcement, 
low cost, low viscosity and ease of processing. Thermoplastics are raising interest for 
their advantages in areas such as: toughness, potential processing advantages, 
recyclability and low volatile emissions; their high viscosity and poor bonding to 
reinforcement are disadvantages [5]. Tough resins are generally formulated by adding 
elastomeric or thermoplastic compounds to the more brittle thermoset resin base. 
Elastomers generally have too low of an elastic modulus to serve as a matrix for rigid 
structural composites.
The selection of a resin involves several factors. Chemical characteristics such as 
resin viscosity, glass transition temperahire, gel time, cure cycle, injection pressure, 
thermal stability, shelf life, environmental resistance, and volatile emissions during 
processing, are some of the parameters that need to be considered in order to determine 
operating and processing conditions for a specific resin.- Mechanical properties such as 
strength and elastic modulus in certain directions, interlaminar fracture toughness, and 
environmental resistance are major composite properties to which the matrix must
5contribute [5].
The most common thermoset resins used as composite matrices are unsaturated 
polyesters, epoxies, and vinyl esters. These resins offer good processability for liquid 
processing techniques such as RTM. The nature of the RTM process and the 
requirements of the wind turbine blade applications demand that the resin system should 
meet the target requirements shown in Table 2.1. Of these, the resin modulus is 
important in maintaining composite compressive strength, particularly under hot, wet 
conditions.
,
Table 2.1 Preferred resin characteristics.
Low cost_____________________________
Resin elastic modulus of 2.75 GPa or higher 
• Resin viscosity from 100 to 500 cps 
Glass transition temperature of 70 C or higher
Low moisture absorption________________
Gel time of at least 20 minutes____________
Room temperature cure preferable_________
Tough resin preferable__________________
Currently, unsaturated polyester resins are the most common systems used in 
composites by the wind industry for the manufacture of blades. They are the most 
affordable, are easily processed, and possess adequate mechanical properties. However, 
most polyesters are brittle resins and have a low temperature resistance and significant 
moisture sensitivity. Vinyl esters are a chemical mixture of unsaturated polyesters and 
epoxy resins. The result is a resin that has mechanical, thermal and chemical properties 
similar to epoxies, with the ease of processing and high rate of crosslinking of 
unsaturated polyesters [5]. Vinyl ester resins are also stiff and brittle, but tougher than
6polyesters due to the presence of the epoxy backbone [6]. Epoxy resins are widely used 
for high performance composites, especially in aerospace, military and sports industries 
[7]. Epoxy resins generally offer an increase on mechanical properties compared with 
polyesters and vinyl esters, but at a higher cost [3]. Another disadvantage of epoxies is 
their relatively high water absorption rate when compared to vinyl esters [8]. The nature 
of curing for thermosets is explained in the following section. Details of each of the 
mayor thermoset resin materials are described later.
Polymer Overview
A polymer is a long molecule containing atoms held together by primary covalent 
bonds along the molecule; secondary bonds act between molecules [7]. The secondary 
bonds are an order of magnitude weaker than the covalent bonds. In general, 
thermoplastic polymers consist of separate molecules held together by secondary bonds. 
Thermoset polymers, when cured, form a three-dimensional network of covalent bonded 
segments, with secondary bonds acting between adjacent segments between the 
crosslinks [9].
Thermoplastics can be separated into two subgroups, semi-crystalline and non­
crystalline (amorphous). Thermoplastics are linear or branched polymers which melt 
upon heating when the thermal energy is adequate to overcome secondary bonds. When 
melted, thermoplastics have relatively high viscosity which restricts available processing 
methods. Thermosets are cross-linked network polymers which are amorphous and can 
not be melted once the network is formed during curing. Thermosets have a relatively
7low viscosity prior to curing, which provides for convenient processing with adhesives 
and composites. They are also very reactive prior to curing, which allows for good 
bonding to reinforcement [10]. Curing occurs after the product is in its final form.
In amorphous polymers, molecules can slip relative to each other without 
breaking covalent bonds. Chain slippage provides high strain to failure, toughness and 
damage tolerance. Semi-crystalline polymers have increased strength and temperature- 
environmental resistance compared with amorphous thermoplastics. In thermosets, cross- 
linking is the process in which covalent bonds are formed between molecules through a 
chemical reaction creating a giant three dimensional network. The polymer chains 
between crosslinks are now not as free to slip relative to each other, and thermosets have 
improved elastic modulus, creep resistance and thermal/environmental resistance relative 
to thermoplastics, but at the expense of relatively brittle behavior [11].
When crosslinks are formed in thermosets, the liquid polymer starts losing its 
ability to flow since the molecules can no longer slip past one another. Curing is the 
process of extending polymer chain length and crosslinkmg chains together into a 
network. The molecular weight increases with the growth of the chain and then chains are ■
i
linked together into a network of nearly infinite molecular weight. Curing is evident 
when there is a sudden change of the resin from a liquid to visco-elastic mass called a gel 
[12]. From a processing point of view, gelation is a critical factor because the polymer 
does not flow and is no longer processable beyond this point. The mechanism of curing 
differs for each polymer group, as discussed later.
Fiber reinforcements used in this research project are E-glass fibers manufactured
8by Alpha Owens Coming. The fibers are coated with silane, a coupling agent. The reason 
for coating the fibers is to improve the fiber/matrix interfacial strength and moisture 
resistance through both physical and chemical bonds, and to protect the fiber surface 
from abrasion during handling conditions. The chemical structure of silane is represented 
by R' - Si(OROS), in which the functional.group R' must be compatible with the matrix 
resin in order to be effective. The silane film reacts with the resin to form a chemical 
coupling between fibers and matrix [10]. Compatibility of the coupling agent with 
different resin systems is generally provided in the company data sheets for a specific 
fabric. The product is coded as P YB, if the coupling agent is compatible with polyesters, 
vinyl esters and epoxy resins, as was the reinforcement used in this study.
Curing parameters and chemical agents which cross-link a resin are different for 
each specific type of resin. A system which only needs a catalyst to start the curing 
process is said to be promoted. A system which needs chemical compounds in order for 
the catalyst to start the. cross-linking reaction of a resin is called an un-promoted system. 
Epoxy resins are usually obtained in a two or three part system which reacts when mixed 
together at the proper temperature. The reason suppliers often provide unpromoted resins 
to users is because the amount of promoter added to a resin will directly affect the 
processing time and shelf life. The Dow Chemical Company for example, provides tables 
for Derakane vinyl ester products that enable the user to achieve different gel times 
depending on the type of catalyst [13]. 1
Properties of Polymers
Thermal Properties
A major concern in the application of composite materials is with the elevated 
temperature properties and the maximum use temperature; these properties are dictated 
by the polymer matrix. The glass transition temperature (Tg) is defined as the temperature 
at which mobility between molecules and segments in amorphous regions is possible. 
Above this temperature the polymer is rubbery; below it, the polymer is rigid. A partially 
crystalline polymer retains some rigidity up to the melt temperature, Tra, which is higher 
than Tg, even though the amorphous part of the material is soft and rubbery. The glass 
transition temperature is the point where there is adequate thermal energy to overcome 
secondary bonds; thus, segments of chains are then free to move, restrained at points of 
crosslinking (thermosets), chain entanglement (amorphous thermoplastics) or crystallites 
(semicrystalline thermoplastics). The polymer softens significantly as Tg is approached. 
The mayimnm use temperature for an amorphous polymer used as a composite matrix is
usually below Tg [9].
The specific heat capacity of a polymer is higher when the molecules are free to 
move, so it decreases with decreased cross-linking, and increases with temperature 
increases, as Tg is approached. A differential scanning calorimeter (DSC) apparatus 
represents one way to measure Tg trough heat capacity change. The DSC measures the 
difference in enthalpy and weight between a sample and a reference material, both 
subjected to a controlled temperature program [9]. Measurement of Tg for the thermosets
10
used in this study proved difficult, particularly when wet.
Another method to estimate the temperature at which a polymer softens is called 
the heat deflection temperature (HDT) [12]. This technique determines the temperature 
when bending deflection at a constant stress increases rapidly. Details are described later.
Tension and Compression
Tension and compression tests are used to determine the yield and ultimate 
strengths and ductility of a material. For a composite material, the stress-strain response 
is a function of the matrix and fiber properties. For a unidirectional composite, the slope 
of the stress-strain curve (Figure 2.1), the longitudinal elastic modulus, Eu,can be 
accurately predicted by the rule of mixtures:
En = Vf Ef + Fm, • Em (2.1) ’
where:
Ef = fiber modulus 
Em= matrix modulus 
V f = fiber volume fraction.
Vm= (I - Vf) if no porosity is present.
In the transverse direction, perpendicular to the fiber axis, the modulus E22 is 
approximated by Halpin-Tsai relationship [14],
11
where:
rj = (£12 f /  Em — Y)/(Enf / Em-
Enf = Ef/2 -(l + v)
and
v = Poissons ratio 
Eizf = shear of modulus fiber
Cd = curve fitting factor given as 2 for E22 [14] 
ri= curve fitting factor
, In polymer matrix composites, the transverse modulus is dominated by the matrix 
modulus, while the longitudinal modulus is dominated by the fiber modulus. The stress- 
strain curve for unidirectional materials is usually approximately linear to failure. The 
tensile strength in the longitudinal direction occurs approximately when the strain m the 
fiber reaches a value close to the fiber ultimate strain. The transverse strength (and shear 
strength) are matrix dominated, with the mode of failure being a crack growing parallel to 
the fibers in the matrix and fiber/matrix interface. The limiting value for the transverse 
tensile strength is the matrix ultimate strength. For brittle resins and/or poorly bonded 
fibers, the transverse strength will, be lower than the matrix strength [15]. The 
compressive strength of unidirectional composites in the longitudinal direction is also a 
matrix dominated property for most glass fiber composites [15]. Failure occurs when the 
fibers locally buckle or kink in the matrix; the matrix provides lateral resistance against 
buckling. The compressive strength can be approximated by:
12
c  = GmI 2(1 + v/) (2.3)
where:
Gm = Em / 2(1 + V)
a  = predicted compressive strength 
Gm= shear modulus of resin 
v = poisons ratio of resin 
Em = tensile modulus resin
This formula assumes perfect fiber alignment and tends to significantly 
overestimate the compressive strength [14]. Most composites are used with layers in 
various directions. The ply layup used for multidirectional laminates in this thesis was 
mostly [0/+45/0]s, where S indicates symmetry about the mid-thickness; thus, this is an 
eight ply laminate. This laminate was tested in both the 0 and the 90 directions. The 
stress-strain curve for a multidirectional laminate is a function of the stress-strain 
behavior of each ply, transformed to the overall laminate coordinates. Stress-strain 
response is usually predicted by a laminated plate theory based software program .[12]. A 
typical stress-strain curve for a multidirectional laminate in tension would then include 
nonlinear responses where off-axis plies cracked, with the ultimate strength dominated by 
O0 layers if there are any present (Figure 2.1).
Strain to failure
Ultimate
strength
Stress.
stress
E= a/s
Strain.
Figure 2.1 Laminate stress -  strain curve.
Ifthere are no O0 fibers present in the direction considered, then the knee strength 
is the most important value for design. It gives the designer an estimate of how much 
elastic elongation the material can tolerate prior to significant matrix cracking. The stress 
at which the knee strain occurs is called the 0.2 % offset knee stress, calculated by 
drawing a parallel line (that has an origin at 0.2 % strain) to the linear portion of the 
stress-strain curve until it intersects the curve (Figure 2.2) [16]. This is similar to the 
usual method used to define the yield stress in metals and polymers. The neat matrix
yield stress was calculated in this manner in this study.
Figure 2.2 Knee stress at 0.2 % strain.
Polymer Chemistry
Polyester Resins
Polyester resins are formed by reacting a diacid and a dialcohol by condensation 
polymerization to form an ester. Orthophthalic polyesters are prepared by combining 
phthalic anhydride with either maleic anhydride or fumaric acid. A combination using 
isophthalic acid or terephthalic acid results in an isophthalic polyester, which has better 
thermal stability, chemical resistance and mechanical properties than orthophthahc 
polyester, but also a higher cost. The number of repeating units for a typical polyester is 
in the range 10 to 100. Because double carbon-carbon bonds are called unsaturated 
bonds, the thermoset polyesters containing these bonds are called unsaturated polyesters 
[17]. After the polymerization is done and depending in the number of units, a highly 
viscous liquid may result. For further processing, polyesters are dissolved in low 
molecular weight monomers such as styrene (the most widely used), also known as 
solvents. Unsaturated polyesters usually contain 35-50 percent monomer by weight.
15
Polyesters are cured by using organic peroxides as initiators, such as methyl ethyl 
ketone peroxide (MEKP) or benzoyl peroxide (BPO). The initiator reacts with the 
carbon-carbon double bond forming a new bond and another free radical on the carbon 
(Figure 2.3). This new radical reacts with another carbon-carbon double bond to form a 
new bond and another free radical. Typical concentrations of initiators is one to two 
percent. Higher or lower concentrations of initiator will result incomplete cross linking 
with inferior properties. Cross-linking takes place when carbon-carbon double bonds 
from separate molecules are linked together, creating a giant three dimensional molecule, 
increasing the molecular weight of the polymer. Monomers also take part in the 
crosslinking reaction since they contain active carbon-carbon double bonds and they 
serve as bridges between polyester molecule chains. One disadvantage of the solvents is 
that they are volatile and their vapors are deposited in the environment when processing. 
One advantage of polyester is that crosslinking does not generate by-products; this makes 
them easy to mold (this is true for epoxies and vinyl esters as well) [5].
The mobility of molecules decreases as molecular weight increases and the 
viscosity is increased; the reaction stops when free radicals are prevented from finding 
new double bonds. An increase in temperature during the curing process will allow 
increased mobility and the creation of more free-radicals. Post cure; is a process that 
increases Tg in a resin because it allows the completion of crosslinking by eliminating 
reactive sites. Often the highest temperature reached by a room-temperature crosslinking
polyester (with exothermic curing) will become its Tg [7],.
Mechanical properties of cured polyester resins are affected by the monomer type
16
and amount, acids, and curing temperatures. Orthophthalic polyesters are the least costly 
form of unsaturated polyesters but they have limited mechanical, properties and 
sensitivity to environmental conditions. Isophthalic polyesters are more costly but they 
show higher tensile and flexural properties due to the higher molecular weight and more 
linear chains [3]. The reaction between a polyester resin and a free radical (provided by 
the catalyst) is shown on Figure 2.3.
Vinvl Ester Resins
Vinyl ester resins are obtained by reacting and unsaturated acid with an epoxy. 
The reaction of methacrylic acid and bisphenol A (BPA) epoxy resin dissolved in styrene 
monomer is the most common version of vinyl esters [18]. An advantage of vinyl esters 
is that the cross-linking reaction is identical to the free radical crosslinking of unsaturated 
polyesters. A structure of BPA vinyl ester is shown on Figure 2.4. The crosslinking 
density of BPA vinyl esters decreases as the molecular weight of the epoxy increases: 
because the methacrylate sites of crosslinking are at the ends of the molecular chain. 
Novolac epoxy vinyl ester resins offer an increased number of crosslinking sites along 
the backbone which raises the final Tg of the resin and the temperature resistance. The 
crosslinking reaction of vinyl esters is identical to the free radical crosslinking of 
unsaturated polyesters; it also uses similar initiators and inhibitors. The double carbon- 
carbon bond is located at the end of the units only (Figure 2.4). MEKP, BPO and 
Trigonox are common catalysts for vinyl esters, used in ranges from I to 2% volume. 
Trigonox catalyst is known for its non-foaming character with vinyl esters. Cobalt 
Naphthalene is a promoter and is usually added to the resin from 0.2 to 0.4% by weight.
17
Vinyl esters are well known for resistance to environmental conditions because 
their high reactivity achieves complete curing easier and faster than for polyesters. Vinyl 
esters have higher elongation to break than polyesters, which also makes them tougher. 
The chemical resistance of vinyl esters is generally greater than for polyesters because of 
the influence of the methyl group [5].
Epoxy Resins
Epoxy resins are generally formed by the three membered epoxy group ring. The 
most common type of epoxy used is known as the diglycidyl ether of bisphenol A 
(DGEBA) (Figure 2.5). Epoxy groups could be located in different locations other than 
the ends [17]. At least two epoxy groups have to be on the polymer molecule for 
crosslinking. Epoxies usually have high viscosities at room temperature, therefore 
dilutents that also contain epoxide groups are used to lower the viscosity.
Hardeners are used to crosslink epoxies. Amine hardeners are the most common; 
hardener should be added in amounts such that the number of epoxide groups is 
equivalent to the number of crosslinking sites provided by the hardener [5]. If the 
hardener is added in the right amounts, a well crosslinked structure with the maximum 
properties will result. Some epoxies are formulated to crosslink at room temperature, but 
most epoxies used in composite applications require an increased temperature to initiate 
the crosslinking [3]. Physical and mechanical properties are also improved by increasing 
the molecular weight when curing. As for polyester resins, no condensation by-products 
are formed during epoxy curing reactions.
The toughness of epoxies depends bn the length of the polymer chain between
epoxy groups. Longer chains (higher molecular weight), will result in tougher polymers. 
One disadvantage of long chains is that there are less crosslinks per unit length (lower 
crosslink density), which results in less stiff and less strong materials, with lower 
modulus and heat resistance. Rubber polymers are added to epoxy resins to increase 
toughness.
Epoxies are usually more expensive than unsaturated polyesters, but have 
important advantages. Epoxies are stronger, stiffer, tougher, more durable, more solvent 
resistant and have a higher maximum operating temperature than polyester thermosets 
[5].
Polyurethane Resins
Polyurethane resins can be either thermoset or thermoplastic. Polyurethanes are 
formed by reacting, two monomers, each having at least two reactive groups. Polyol and 
isocyanate monomers are generally liquids that are combined to form the polyurethane. A 
typical polyurethane molecule can be seen on Figure 2.6. Polyurethanes are very versatile 
polymers. The role of the polyol in polyurethane chemistry is like the role of the epoxy 
molecule in epoxy chemistry. The isocyanate role in polyurethanes is like the hardener in 
epoxy chemistry. Polyols have OH groups on the ends of the branches. Polyurethanes 
have superior toughness and elongation to failure, therefore they are used by the 
automotive industry, for example, to manufacture car bumpers [19]. Mechamcal 
properties of polyurethanes will depend in the type of monomer used. Ether based 
polyurethanes have the highest mechanical properties, and they are also known for their 
short and fast solidification times, which makes them suitable for processing methods
with faster injection time such as reaction injection molding (RIM) as compared with 
RTM [17]. There are semi-rigid and rigid polyurethanes. A low glass transition 
temperature caused by the flexible polyol chains is a characteristic of semi-rigid 
polyurethanes which results in good flexibility. Rigid polyurethanes can be used at 
temperatures up to 150 0C due to the cross-link structure of the matrix material [3],
o
Il-HX r —o—C—C = = C - c—o ->ji i
(a) Unsaluralcd polyester with active C =  C site (»)
O
Il
- tC .
New bonds (crosslinks)
- To another molectik
H H -k H
I i T i
c — O— C —  C - C — C —  O-ft
I I
' C - C - ( Q ) I - ------- Styrene
O
Il-tc . c—o—c—c—c—c—o-fe
y  i  u  i
To another molecule — "
(b) Crosslinking of unsaturated polyester
Figure 2.3 Unsaturated polyester showing (a) reactive carbon-carbon double bond and (b) 
crosslinking reaction (from reference 17).
20
ESTER GROUPS
O
- c - LC = C
CH3
O— C— C—C— 
OH
O - C - C - C - O - C - C = C
OH
I to 3
TOUGHNESSEPOXY BACKBONE
■— HYDROXYL GROUP ------1
-  METHYL GROUP SHIELDING --------
TERMINAL UNSATURATION ------► REACTIVE POLYMERIZATION SITE
IMPROVED WETTING & BONDING TO GLASS 
► GOOD CAUSTIC CORROSION RESISTANCE
Figure 2.4 Bysphenol A vinyl ester (from reference 18).
H
Epoxy group
H
(a) Typical Epoxy
. II
Cx-CO
zH :
x H
4
Epoxy group
Amine
hardener
11
H I
C - J C  —  I Polymer)
HZ xOzi I
„  N - H
H
H
x C — C —  (Polymer)
<A  I
/  N O
New bond 3
IBr
2,
K,
H \
New bond
I
(b) Epoxy Reaclion
Figure 2.5 (a) Typical epoxy and (b) epoxy reaction (from reference 17).
(A diisocyanate)IA polyol)
t
O H
!I
—1~ O —  R —  O —  C
(A polyurethane)
H O
I Il
N —  R —  N — ( -frn
Note: R is usually a multifunctional polyether or polyester 
but can also be a small organic group.
R' is usually a large aromatic group
F igu re  2 .6  Po lyu re th ane  reac tion  (from  re fe rence  17).
Resin Toughness in the Composite
The  p rim ary  fac to r de te rm in ing  com posite  de lam ina tion  res is tance  is the 
toughness  o f  th e  res in  m atrix . A  te s t m e thod  u sed  to  charac terize  th e  resis tance  o f  a 
com posite  to  th e  in itia tion  o r g row th  o f  in te rlam ina r c racks is th e  doub le  can tilever beam  
(DCB ) d iscu ssed  in  the  fo llow ing  sec tion  (F igu re  2 .8) [20]. The toughness  o f  a  resin  
sy stem  is n o t a lw ays tran s la ted  in to  th e  com posite  due  to  fiber nesting , b ridg ing , pu ll ou t 
and  b reakage  th a t can  p roduce  an  increase  in  th e  apparen t in te rlam inar G ic o f  a  com posite  
(F igu re  2 .7 ), w h ile  p oo r fiber m a trix  bond ing  m ay  increase  o r decrease  com posite  
toughness . Its has been  observed  th a t to ughened  m atrices res tric t the  c rack  tip
defo rm a tion  zones a ffec ting  th e  d e te rm ina tion  o f  G ic [2].
22
A THERltOSET
" O EXPERIMENTAL
O TOUGHENED
THERM OS ET
+ THERMOPLASTIC
2.0 3.0 4.0 5-0
RESIN Gic  (k J /m  )
Figure 2.7. Composite interlaminar strain energy release rates for steady crack growth 
as a function of the neat resin G,c for different resins systems from reference 7.
DCB and ENF Test Methods
Fracture mechanics treats crack-dominated failure modes. In composites fracture 
mechanics is applied primarily to delamination between plies. There are three different 
modes in which delamination takes places in a composite under different loading 
conditions: opening; (I), shearing (II) and tearing (III) [21]. For a fracture to occur, a crack 
has to be initiated and then propagated. In fracture mechanics terms, initial crack growth 
occurs when the energy release rate G equals the crack resistance of the material [22]. 
Initiation fracture toughness in mode I, (GIC), is a material property used in materials 
selection and design. The most widely used method to test mode I delammation is the 
double cantilever beam (DCB) test described in the ASTM D 5528 [23,25], Geometry 
and loading for this test can be seen in Figure 2.8. End notched flexure (ENF) is a test 
method developed to test mode II delamination and is explained in detail in Chapter 3.
APiano hinge Insert
Adhesive
Figure 2. 8 Geometry and loading for a DCB specimen.
Skin Stiffener Structure
Skin stiffener structures are used in wind turbine blades to transfer shear loads 
and increase bucking resistance. Delamination is a failure mode and a major concern in 
this type of structure [24]. The flange is bonded to the skin by the matrix (Figure 2.9); 
therefore, it is important to study delamination effects when using different resins. Initial 
damage load, maximum loads and displacements are recorded as shown in Figure 2.10.
24
Load
Stiffener
9.9 cm
Test Fixture
5.0 mm
Flange
3.9 mm5.3 mm
12.7 cm
Figure 2.9 Loading and approximate dimensions for skin-stiffener T-specimens.
Maximum load & 
displacement at 
maximum load
o 150
S 100 Initial damage load & 
displacement at initial 
damage.
Displacement (cm)
Figure 2.10 Typical load-displacement curve for a skin-stiffener specimen.
25
CHAPTERS
EXPERIMENTAL METHODS 
Polymer Resin Systems
Thermoset resins including polyesters, vinyl esters, epoxies and one urethane 
were investigated. The polyester CoRezyn 63-AX-051 manufactured by Interplastics 
Corp, is an unsaturated orthophthalic polyester resin, has been used by industry to 
manufacture wind turbine blades and is the resin used for most of the DOE/MSU 
Database [I]. The CoRezyn polyester has been extensively researched and therefore is 
considered as the baseline polyester to compare with other systems.
Two other polyester systems were studied briefly, a PET-Polyester P460 from 
Alpha Owens Coming and an unsaturated polyester Arotran Q 6038 from Ashland 
Chemicals. The Arotran polyester was selected because of its intensive use in the 
automotive industry on applications such as body panels for the Chrysler Viper. The 
three polyesters were catalyzed using 2% by volume Methyl Ethyl Ketone Peroxide 
(MEKP). Gel times for polyester resins were on the order of 30 to 40 minutes, with 6 to 
15 hours cure time. Finished parts were postcured by in an oven for two hours at 60 °C.
Vinyl esters are gaining acceptance in wind blade manufacture and in several 
other composite materials uses primarily due to improved properties and lower viscosities 
and ease of manufacturing. Four vinyl esters where studied, th e  first two were obtained
26
from TECTRA Inc.: Swancorp 980 which is an elastomer-modified vinyl ester diluted in
styrene monomer, and Swancorp 901, which is an epoxy-novolac based vinyl ester 
diluted in styrene monomer. Two additional vinyl ester resins were obtained from Dow 
Chemical, Derakane 411C-50 and Derakane 8084 (rubber modified), which were both 
epoxy vinyl ester based systems. These resins were unpromoted as received (except the 
second batch of Derakane 8084). Cobalt Naphthenate-6% (CoNap) was used to promote 
them using the amounts shown in Table 3.1. Trigonox 239A was the catalyst used to cure 
vinyl ester resins since it did not cause foaming of this type of resin as did MEKP. Table 
3.1 shows the amount of promoter and catalyst used in each vinylester resin [13]. 
Formulations were mixed by volume and estimated for a 20 °C processing temperature. 
All plates were postcured for two hours at 60 °C.
Table 3.1 Catalysts,'promoters and curing conditions for vinyl ester resins.
Vinyl Ester Resins 
(Mixed by volume)
Gel Time 
20-40 Minutes
Demold Time Mold Release
Swancorp 901, 
50-50% Blend 
Swancorp 901 & 980, 
and
Derakane 411c-50
2.0% Trigonox 239A 
0.3% CoNap
IOto 14 hrs 
10 to 14 hrs
A 1380
Derakane 8084 
Swancorp 980
2.0% Trigonox 239A 
0.5% CoNap
8 to 12 hrs A 1380
The epoxy resins used were: System 41, a two part epoxy system referred as an 
RTM laminating resin from System Three. The other two epoxies were obtained from 
Applied Poleramic Inc. Both resins were two phase - acrylate modified epoxies. Epoxy 
SC-12 is a three part system while epoxy .SC-14 is two part. Table 3.2 shows mixing 
ratios and curing cycles for the epoxy resins used. SC-12 and SC-14 cannot be demolded
27
or un-clamped until the cure cycle is completed.
Table 3.2 Mix ratios and cure conditions for epoxy resins.
Epoxy Resins Mix ratio by 
weight (A:B:C)
Cure Cycle Post Cure Cycle Mold Release
System 41
SC-12
SC-14
4,1
100,80,20
100,35
12 hr at 20 °C 
I hr at 60 °C 
3 hr at 60 °C
2 hrs at 60 °C 
2 hr at 90 °C 
5 hr at 100 °C
A1380
Monocoat E-91 
Monocoat E-91
The urethane was a liquid polyurethane plastic formula Poly 15-D65 from 
Polyteck Development Co. The mixing ratio for this resin was one part of part A to one 
part of part B. The injection time for this resin is 20 minutes and a de-mold time of 16 
hours. Finished parts were postcured for 2 hours at 60 °C.
. Test Methods
Three specimens of each resin type were tested in most cases. Average values and 
standard deviations calculated. Ifless than three specimens were tested, no standard 
deviation was calculated.
Delamination Tests
Composite delamination tests were run in Mode I with DCB specimens and Mode 
II with ENF specimens as described earlier. For the Mode I DCB tests, specimens are 
prepared with an even number of unidirectional plies, with delamination occurring in the 
zero direction [26]. A Fluoro-Peel teflon release film (30 pm thick) which does not bond 
to the resin (in this case) is placed at the mid-thickness of the laminate when it is 
fabricated, to function as a crack starter. Hinges are attached to the specimen as a means 
of transferring load. Modified beam theory (MBT) is used to calculate the Mode I critical
28
strain energy release rate:
Gic = (3-Pc-S)/(2-b ■ a) (3.1)
where:
Pc= critical load at the onset of nonlinearity (shown on Figure 3.2)
8= load point displacement at Pc 
b= specimen width
a = crack length measured from hinges
Mode II delamination resistance, also known as the forward shear delamination 
resistance (Gnc) is generally measured using the end notch flexure (ENF) specimen [27]. 
The specimen is manufactured with a crack starter and the test consists of a three point 
bending load. Specimen dimensions and loading geometry are shown on Figure 3.1. 
Unstable crack growth is generated when the maximum load is applied to a ENF 
specimen. The mode II fracture energy was determined from the following equation used
by Mandell and Tsai [28]:
G/;c =  (9 a" ^ ) / ( 1 6  E  ^  ^ )  (3.2)
Where:
P = maximum load for crack extension 
a = crack length measured from the outer pin 
E = longitudinal elastic modulus 
W= specimen width
h= half thickness of the specimen
P
i
~ T
Fixture supports
Figure 3.1 Geometry and loading for ENF
Equation 3.1 was used to calculate the strain energy release rates for Mode I using 
the different resin systems. The critical load used in the MBT equation was taken from 
onset of non-linearity in the load displacement plot shown in FIG. 3.2. For some resins, 
there was a linear load displacement response until the crack was propagated. For other 
resins, the load displacement curve was nonlinear and the crack extension point was 
taken as the onset of non-linearity (Figure 3.2).
2  15
Non linearity 
pointsS 10
disp (cm)
Figure 3.2 Load-displacement plot for a DCB test.
-I k-
During the ENF testing, the load was increased on the specimen until i t , 
experienced a sudden and unstable crack growth. The value of the energy release rate for 
Mode II (One) was then estimated using this value of maximum load. Specimens were 
pre-cracked in Mode I using the criteria suggested Carlsson and Gillespie [22] to generate 
unstable crack growth. For stable crack growth, the critical load can be used to generate a 
more conservative Gnc value [29]. The longitudinal modulus E was calculated for each 
resin using the correlation for different fiber contents given by Mandell and Samborsky
[I]:
(El / El *) = (1 /32 .71X3.1+65.8^  (3.3)
This equation adjusts approximately linearly the longitudinal modulus El with 
fiber volume fraction VF, where El * indicates the property at the 45% fiber volume with
f
a lay-up of [0]6 in Table 9a of reference [I]. This equation was developed for the 
polyester matrix, and will not be accurate for low modulus matrices.
Skin Stiffener Test
1
The test geometry and loading conditions were given in Figure 2.9. The T- 
Specimens were tested under a tensile load in the same manner as described by Haugen 
[24]. The initial damage load and displacement at initial damage are recorded as the onset 
of non-linearity on a load-displacement plot. The maximum load and displacement at 
rrmvimnm load may be reached before the specimen fails (Fig 2.10), with the load 
decreasing as damage accumulates at higher displacement. Molding and ply 
configurations for skin, flange and web are discussed later.
31
Heat Deflection Temperature
A rectangular neat resin specimen is subjected to a three point bending load while 
immersed in a heat transfer medium (Figure 3.3) [30]. The temperature is raised at 
uniform rates, between 0.2 to 2 °C/min. The temperature of the medium is measured 
when the test bar has deflected 0.25mm. The deflection versus temperature is plotted for 
each specimen as shown in Figure 3.4. The plots were initially adjusted to a zero 
displacement due to the.negative displacement caused by the initial deflection of the test 
coupon under load. The result of this test is called the deflection temperature under 
flexural load [30]. The load is calculated as follows.
f . =  (2  ,S' 6 ^ / 3 1  (3.6)
Where: P = load .
S = maximum stress in the specimen of 1820 KPa
b = width of specimen 
d = depth of specimen 
L = span between supports
Hp-Data
Ceramic
rod
Convection
Thermocouple
Neat resin
b = 1.27cm
L = 12.7 cm
j) h = 3 mm
7.37 cm<t) = 0.3162 c:
55.88 cm
Supports
WeightFixture
Figure 3.3. Schematic of heat deflection test
A convective Lindberg Blue oven Model MO 1450 C was adapted by Samborsky 
perform the HDT Test following the ASTM D648 standard [30]. Figure 3.3 shows the 
settings for the test. A ceramic displacement rod and a type K thermocouple were 
attached to an HP Data Acquisition System (Model HP 34970A) to record displacement 
and temperature. The ceramic rod was chosen because of its well known low coefficient 
of thermal expansion. The thermocouple was supported on the fixture touching the 
specimen on one side and did not interfere with the deflection. The constant heating rate 
selected and used for all resins was 0.3 °C/min. The tests were run until a mid-span 
deflection of at least one millimeter took place (Figure 3.4)
33
E
&  0.25
S  0.2
® 0.15
I  0.1
£ 0.05 
a. 0 
.!2
Q
Temperature (C)
Figure 3.4 Displacement -  temperature curve for a HDT test.
M anufac tu ring  P rocess
All the materials except stiffeners were manufactured as flat plates at Montana 
State University -  Bozeman by resin transfer molding. Three different molds were used 
depending on the specimen type and size. For DCB, ENF, tensile and compressive 
specimens, rectangular flat plates with dimensions of 42 x 14 cm were cured using an 
aluminum mold labeled as Mold A. This mold was also used to cure pure resin plates for 
tensile specimens for each resin, as well as heat deflection temperature (HDT) specimens. 
Mold A was placed vertically when injecting pure resin, letting the resin flow from the 
one end to the bottom in order to let the let air bubbles in the resin rise to the surface. The 
bottom port was closed off, using one of the two top ports to inject the resin and the other
as a vent port.
The second mold (Mold B) also called the T-Mold was used to manufacture skin- 
stiffener T -  specimens. This mold was designed by Haugen [24]. Mold B had 
dimensions of 16x46 cm for the skin and 10x46 cm for the flange. The resin was
34
injected using a peristaltic pump from Cole Parmer Co (Model 7553) with Mold A and 
Mold B. Once the fibers were wetted out by the resin the vent ports were closed off and 
the resin cured inside the mold for a period of time different for each resin. The injection 
pressures for the three molds were less than 150 KPa and adjusted depending on the fiber 
content and lay-up.
Specimen Preparation and Testing Equipment
Composite test specimens consisted of either unidirectional [0]6 or [0/±45/0]s 
configurations. Reinforcements were primarily unidirectional E-Glass stitched fabric 
Knytex D155 and double bias (+45A45) DB120. After postcuring, test specimens were 
machined with a water cooled diamond blade saw. The lay-ups, fiber volume (Vf) 
content, and average thickness for the different specimens are shown in Table 3.3. Ply 
configurations for T - specimens are shown in Table 3.4
Table 3.3 Lay-ups, fiber volumes and thickness for different tests.
Specimen Type Lay-up Type of 
Fabric
Vf Average 
thickness (mm)
DCB FOl6 D155 40 3.4
ENF roi6 1 D155 40 3.4
Transverse Tension r90/+45/901s D155/DB120 37 3.0
Compression r0/+45/01s D155/DB120 37 3.0
Vf= Fiber volume (%)
35
Table 3.4 Ply configuration and average thickness for skin-stiffener specimens.
Region Ply configuration Average 
thickness (mm)
Skin [+45/-45/02/+45/-45]s 4.3
Flange [+45/-45/02/+45/-45] 1.5
Web [+45/-45/Q2/+45/-45]s 4.5
Interface (45/-45)
Skin + flange 6.0
The majority of the test specimens (except T-Specimens) had a rectangular flat 
shape. Selected tensile and compressive specimens were soaked in water for 330 hours at 
50 0C as pure resin and composite samples. Dimensions for tensile and compressive 
specimens and for water absorption tests are shown on Table 3.5.
Table 3.5 Dimensions for tensile, compressive and water absorption specimens.
Specimen Type Dimensions (cm).
Tensile Specimens 15.24x2.54
Compressive Specimens 12.7x2.54
Specimens For 
Water Absorption
5.08x1.27
DCB and ENF delamination specimens had a an average length of 17 cm and a 
width of 2.54 cm. These specimens where manufactured with a Fluoro-Peel Teflon 
release film that was inserted at the mid-plane of the laminate to serve as a crack 
initiation site according to ASTM 5528 [23]. Removable pin hinges (N121-606:V508) 
were bonded to the end of each DCB sample on both sides using and adhesive Hysol EA 
9302.2NA. DCB and ENF specimens can be seen at Figure 3.5
36
F igu re  3.5 DCB  and  ENF  specim ens.
A n  In stron  8562 servo  e lec tric  te s tin g  m ach ine  w as u sed  to  p e rfo rm  all the  static  
te sts  in c lud ing  tension , com pression , T -Pu ll o ff, DCB  and  EN F . F o r a ll te sts  a  load  cell 
ca lib ra ted  to  its  respec tive  A STM  standard  w as used . T ensile  te sts  on  com posite  and  
pu re  re s in  spec im ens w ere  perfo rm ed  by  a ttach ing  an  ex tensom ete r (C lass  B2) to  the 
sp ec im en  u s ing  rubber bands. T he  fix tu re  show n  in  F igure 3.6 w as u sed  to  apply  
com press iv e  loads on  ENF  bend ing  spec im ens and  tensile  loads on  T -Spec im ens. T ab le  
3 .6  show s d isp lacem en t ra te s  u sed  fo r th e  d iffe ren t tests.
T ab le  3.6 T es t ra tes for d iffe ren t tests.
Testtype Test rate (cm/min)
DCB 0.01
ENF 0.64
Tensile test in resin 0.51
Tensile test in composite 0.38
T-Pull off test 0.64
Compression Test 76
37
F igu re  3 .6  T e s t fix tu re  u sed  fo r ENF  and  T -S pec im ens
Test fo r DCB  and  EN F  Specim ens
T h ree  se ts  o f  te s ts  w ere  perfo rm ed  on  D CB  spec im ens (see  A ppend ix  B). O n  the  
firs t se t o f  D CB  te sts  as recomm ended  by  th e  A STM  5528 s tandard  [23], spec im ens w ere  
n o t p re -c rack ed  in  o rder to  o b ta in  an  in itia tion  v a lu e  o f  Gic free  from  any  fiber b ridg ing  
ac ro ss  th e  c rack  fron t fo r all the  d iffe ren t res in s . T he  values fo r Gic con sid ered  to  be  the  
in itia tio n  v a lu es  w ere  th en  ob ta ined  from  th e  second  te st pe rfo rm ed  on  each  spec im en  
(a fte r I to  3 m m  o f  c rack  grow th), w h ich  is equ iva len t to  p re -c rack ing  a  specim en.
D av ies  and  B enzeggagh  [21] recomm end  p re -c rack ing  the  spec im ens, considering  th a t 
G ic va lues  are  m ore  accu ra te  w hen  fiber b rid g ing  occurs. The second  se t o f  tests w as 
p e rfo rm ed  on  a  50 -50%  b lend  o f  Sw ancorp  v iny les te r  resins b e tw een  a  rubber m od ified  
v iny l e s te r  Sw ancorp  980  and  a  p lane v iny l e s te r  Sw ancorp  901 to  s tudy  th e  e ffects  on  th e  
frac tu re  toughness  w hen  b lend ing  com patib le  res in s . Pure resin  ten s ile  m odu lu s w as a lso
38
measured on the Swancorp blend.
A separate set of tests was performed for DCB specimens manufactured with the 
unidirectional UC1018/V experimental fabrics. These fabrics have bonded unidirectional 
fiberglass on one side and a thin veil on the other side, which holds the fibers. Two 
different types of veils were used, polyester and glass veil. Lay-up configurations are 
shown on Table 3.7. The UC1018/V, D155 and DB 120 fibers can be seen in Figure 3.7. 
The motivation of this test was to study the changes in the delamination toughness when 
using different fiber reinforcements, using polyester resin CoRezyn 63-AX-051.
Table 3.7 Geometry and lay-ups for DCB specimens using UC1018/V fabrics.
Veil Type Placement at the mid-plane Lay-up
Polyester Veil Veil-Veil 1016
Glass Veil Veil-Veil [0] 6
Polyester Veil Glass-Glass rou
D155 UC1018V
iieWesi
DB120
2 cm
Figure 3.7 Different fabrics used.
39
CHAPTER 4
RESULTS AND DISCUSSION 
Introduction
This chapter presents the results of this study, first considering the neat resin 
behavior and heat deflection temperature; followed by composite interlaminar fracture 
toughness, T-stiffener pull-off, transverse tensile strength, compressive strength and 
moisture effects. The resin systems are then compared in terms of cost versus overall 
performance and processing characteristics. Complete details for each test can be found 
in the Appendix.
Neat Resin Properties
Tensile Stress-Strain Curves
Results for tensile modulus, yield stress, ultimate tensile strength (UTS) and strain 
to failure for different resins are shown in Table 4,1. Tensile stress - strain curves for 
various neat resins are given in Figure 4.1.
40
Table 4.1 Tensile test results for neat resin.
Resin UTS
MPa
Yield strength 
MPa
Modulus, E 
GPa
Failure 
% strain
CoRezyn 63-AX-051 54.07
(4.64)*
45.19
(2.47)
3.18
(0.12)
2
(0J1)
Swancorp 980 (batch a) 25.65
(0.29)
20.56
(0.48)
1.63
(0.02)
29.51
(15.05)
Derakane 411C-50 57.68
(0.78)
50.39
(2.49)
3.21
(0.04)
2.06
(0.06)
Derakane 8084 72.57
(2.73)
55.16
(2.39)
3.25
(0.15)
2.97
(0.31)
System 41 52.61
(1.08)
52.61
(1.08)
3.57
(0.06)
1.60
(0.05)
Epoxy SC-12 44.34
(3.06)
** 3.48
(0.04)
1.38
(0.12)
Epoxy SC-14 68.31
(2.68)
48.50
(1.33)
2.80
(0.03)
3.31
(0.27)
* (Std. Deviation)
**No clear yield stress prior to fracture
Vinyl ester 
8084
SC-14
Polyester 
63-AX-051 Swancorp 980 (a)
Strain (%)
Figure 4.1 Stress-strain curves for tensile tests of neat resins.
The tensile modulus and ultimate tensile strength are similar for the majority of 
the resins except for the Swancorp 980, which is lower. Toughened resins (excluding 
epoxy SC-12), such as Derakane 8084, Epoxy SC-14 and Swancorp 980 (a) tend to have ■ 
a higher ultimate strength and strain to failure compared to the untoughened base resins. 
Epoxy System 41 has the highest resin modulus. It is shown later that higher resin 
modulus is associated with lower interlaminar toughness, but higher composite 
compressive strength. Swancorp 980 (a) had the highest strain to failure, showing a 
ductile behavior, but a lower E than the 2.25 GPa target given earlier for wind turbine 
blades. The rubbery urethane was not tested as a neat resin because of its foaming 
character. It is evident form later composites data that it has a very low modulus; but high 
strain to failure.
Heat Deflection Temnerature
Results for heat deflection temperature (HDT) can be seen in Table 4.2. Standard 
deviations for an average of 3 specimens are included. Heat deflection temperatures were 
around 20 0C lower than the glass transition temperatures (Tg) listed by the manufacturer 
of the resins. This is commonly expected because the heat deflection temperature test 
applies a load to force a deflection in the specimen, while the Tg test only applies heat to 
the specimen. The cure and postcure cycles are directly related to the heat deflection 
temperature of a cured resin (discussed earlier). SC-12 and SC-14 were postcured at 
higher temperatures, as shown on Table 3.2, and their HDT temperatures were higher 
than the rest of the resins that were postcured at 60 °C. Derakane vinyl ester resins 
generated more exothermic heat while curing (room temperature processing) and had
42
higher HDT temperatures than the Swancorp vinyl ester resins. Results for CoRezyn 63- 
AX-051 are similar to the epoxy System 41 and the vinyl ester Swancorp 980 batch (b). 
Good consistency of results was observed in most resins. The manufacture's Tg for the 
urethane resin was not provided.
Table 4.2 Heat deflection temperatures for different resins.
Resin Value listed by 
Manufacturer °C
Average 
HDT °C
Standard
Deviation
Specimens
tested
Polyester 63-AX-051 68 (HDT) 55 0.94 3
Vinyl ester 980 batch (b) 82 (Tg) 60 1.73 3
Vinyl ester 411C-50 82 (HDT) 78 3.69 3
Vinyl ester 8084 77 (HDT) 75 1.38 3
Epoxy System 41 51 (HDT) 56 3.64 3
Epoxy SC-12 HS(Tg) 95 1.22 3
Epoxy SC-14 103 (Tg) 83 1.9 3
If 70 °C is taken as a target Tg for wind turbine blades, as discussed, earlier, then 
the acceptable resins were the vinyl esters Derakane 411C-50 and 8084, and the Epoxies 
SC-12 and SC-14. These tests were run at ambient moisture content, and the HDT would 
be lower at higher moisture contents.
Composite Properties
Interlaminar Fracture Toughness
Modified beam theory (Equation 3.1) was used to obtain the results for Gic on 
composite specimens. The first set of DCB tests included ten different matrices. All the 
tests were performed with the same unidirectional lay-up of [0]6 using D155 fabrics with 
the crack growing in the O0 direction. Three values of Gic are recorded for each resin
43
system. Each test corresponds to a loading on a specimen. The first test performed on 
each specimen, denoted test (a), is run without pre-cracking the specimens; this provides 
a Gic initiation value at the artificial crack tip as recommended by the ASTM 5528 [23]. 
The results of test (a) are usually affected by a resin rich area inevitably formed in front 
of starter film as reported by Davies and Benzeggagh [21]. The second test performed on 
each specimen, denoted test (b), involves propagation of the crack previously generated 
by test (a). Test (b) therefore, uses a sharp crack with a tip position 2 to 4 mm beyond the 
original teflon strip (see Appendix). The value from test (b) is affected by slight fiber 
bridging but it provides useful information on the delamination resistance for short 
cracks. Gic values for test (b) are usually higher than values for test (a) due to the fiber 
bridging phenomenon. The third Gic value listed in some cases, the overall Gic, is the 
average Gic value of the all the tests performed on each specimen (Appendix), covering a 
range of crack lengths up to 15 mm. The energy release rate for Mode II, Gnc, was 
determined on the same DCB specimens used to determine Gic after cracks were grown 
in Mode I. The hinges were removed from the DCB specimens and the cracks 
propagated as discussed previously. At least two DCB and ENF specimens were tested 
for each matrix system, usually taken from a single molding.
PoIvester Resins. Three different polyester resins were tested and results for Gic 
test(a), Gic test(b) and Gnc are shown on.Table 4.3. The values obtained for Grc test(a) 
are very similar for the three matrices. The PET P460 modified polyester did not show 
an increase in fracture toughness as expected [31] , but it sho wed an increase of the Gic 
value obtained with test (b). The PET P460 showed the maximum Gnc for polyesters,
44
twice as high as for the CoRezyn 63-AX-051. The maximum loads for the CoRezyn 63- 
AX-051 and the PET-Polyester were relatively low, between 1.5 to 4 kilograms while 
other systems reached 20 kilograms (see Appendix). The maximum load depended 
directly on the initial crack length [29]. Arotran Q6038 had the highest Gic value for test 
(b) but the lowest-One value of all resins. This system was not processed to manufacture 
specimens for other types of test due to its high reactivity and smoke generation while 
curing.
Table 4.3. Gic and Gnc for polyester resins.
Resin Gic (a) initial 
J/m2
Gic (b) 
J/m2
Gnc
J/m2
Specimens
tested
CoRezyn 63-AX-051 153 159 977 4 for Gic
(10)* (29) (229) 3 for One
PET P460 144 219 1866 5 for Gic
(50) (59) (197) 4 for Ghc
Arotran Q6038 153 309 305 I for Gic 
I for Gnc
*(Std. Deviation)
Vinyl Ester Resins. Three yinyl ester resins were tested. Two rubber modified 
versions: Swancorp 980 and Derakane 8084, and one non-toughened vinyl ester, 
Derakane 411C-50. Results for Gic test(a), Gic test(b) and Gnc are shown in Table 4.4 
for the different vinyl ester resins. Toughness was measured on two different batches of 
Swancorp toughened resins, Swancorp 980 (a) and Swancorp 980 (b). Differences 
between Gic values for the two batches of resin are discussed later. Swancorp 980 (a) had 
the second highest Gic value after the polyurethane (discussed later).
Table 4.4. Gic and Gnc for vinyl ester resins
Resin Gic (a) initial 
J/m2
Gic (b) 
J/m2
Giic
J/m2
Specimens
tested
Swancorp 980 (batch a) 1441
(313)*
1840
(161)
3116
(812)
4 for Gic 
3 for One
Derakane 8084 344
(7)
595
(133)
2638
(567)
3 for Gic
4 for Gnc
Derakane 411C-50 234 396 2557 2 for Gic 
2 for One
*(Std. Deviation)
Swancorp 980 (a) had a superior toughness compared to the other vinyl ester 
resins. Its Gic value in test (a) is 6.1 times higher than for vinyl ester 411C-50 and 4.1 
times higher than for the rubber modified Derakane 8084. The toughened vinyl ester 
Derakane 8084 showed an increase in the resin toughness compared to the Derakane 
411C-50, but not very significant in test (a). Figure 4.2 shows mode I and mode II 
delamination in Swancorp 980 (a) and Epoxy SC-14 specimens. Loose fibers indicating 
fiber bridging can be seen on the Swancorp 980 resin. This resin had slow, stable crack 
growth in both modes while Derakane resins had a similar behavior to polyester resins, 
fast and unstable cracks in modes I and II.
Enoxv Resins. Epoxy System 41 is a non-toughened epoxy resin while epoxies 
SC-12 and SC-14 are acrylate-modified systems. SC-14 had the highest Gic value for 
epoxies, 2.9 times higher than system 41, and four times higher than the baseline 
polyester, when comparing test (a) Gic values. However, System 41 had the highest Gnc 
value of all resins (Figure 4.4). One System 41 specimen failed in compression during
46
ENF  te s tin g  (A ppend ix ). E poxy  SC -14 is a  tough  system , bu t it has a  h igh  v iscosity  and  a 
hea ted  m o ld  is requ ired  in  o rd e r to  cu re  it, w h ich  m akes it h ard  to  p ro cess  (see  P rocessing  
O bserva tions). E poxy  SC -12 h as  s im ila r G ic and  Gnc va lues  to  D erakane  4 1 1C-50. 
System  41 is re la tiv e ly  tough , b rittle , low  HDT  and  m odera te ly  expen siv e  fo r an  
un toughened  epoxy . F ib e r b ridg ing  w as no t as ev id en t fo r epox ies  as it w as fo r po lyesters  
and  v iny l e s te rs  (F igu re  4 .2).
T ab le  4 .5 G ic and  Gnc va lues fo r epoxy  resins.
R esin Gic (a) in itia l 
J /m 2
G ic (b) 
J /m 2
Gnc
J /m 2
Specim ens
T ested
System  41 219
(22)*
231
(38)
3776 3 fo r G ic 
2 fo r Gnc
SC -14 638 638 3223 3 fo r G ic
(58) (157) (520) 3 fo r Gnc
SC -12 347 427 2530 2 fo r G ic 
2  fo r Gnc
*(S td . D ev ia tion )
F iber B ridg ing
M O D E I
D elam ina tion
M ODE  II 
D elam ina tion
F igu re  4 .2  M odes I and  II fo r T oughened  Resins.
47
Polyurethane Resin. The thermoset polyurethane is a very ductile, rubbery resin 
with a very high toughness and low Tg. It behaves similarly to a thermoplastic resin 
because it has the ability to stretch without breaking [17]:. The polyurethane resin was 
difficult to test in mode one due to its high content of porosity formed while curing. The 
crack front was difficult to locate since the marker ink used for, this was absorbed by the 
pores. Additionally, only one specimen was tested in mode I because the other two 
specimens lost their hinges during DCB testing. The specimens failed in compression 
when doing ENF testing and no crack growth was generated in mode II. A lower bound 
One value for this resin was calculated using the maximum load that caused the 
compression failure using the initial crack length; no crack growth was generated (Table
4.6)
Table 4.6 Gic and Gnc values for polyurethane resin.
Resin Gic (a) initial 
J/m2
G,c (b) 
J/m2
G iic
J/m2
Specimens
tested
Poly 15-D65 2663 2752 3145* 1 2 for Gic 
I for One
* Did not fail in mode II; lower borne ...
Overall Toughness Comparison. The polyurethane composite resin had the 
highest value for Gic (Figure 4.3). The rubber modified vinyl ester resin Swancorp 980 
batch (a) had the second highest value of Gic- It is shown in Figure 4.3 that Derakane 
411C-50 has the highest Gic for neat resins and similar toughness values to Epoxy SC-12. 
One values are compared in Figure 4.4 for the resin systems studied. Epoxy System 41
had the highest Gnc followed by Epoxy SC-12. PET P460 resin had the lowest 
performance for toughened resins, but higher performance than for non-toughened 
polyesters.
48
1. Cortsyn 63-AX-051
2. Arotran Q6038
3. PET P460
4. System41
5. SC-12
6. SC-14
7. Derakane 411C-50
8. Derakane 8084
9. Swancorp 980
10. Polytek 15-D-65
1 2 3  4 5 6 7 8 9  10
m  Non-toughened resins □  Toughened resins
Figure 4.3 Comparison of Gic test (b) results for different resin systems.
1. Corezyn 63-AX-051
2. Arotran Q6038
3. PET P460
4. System 41
5. SC-12
6. SC-14
7. Derakane 411C-50
8. Derakane 8084
9. Swancorp 980
10. Polytek 15-D-65
u  1 2 3  4 5 6 7 8 9  10
Q  Non-toughened resins □  Toughened resins
UrethaneVinylesters
Polyesters
Figure 4.4 Comparison of Gnc results for different resin systems.
49
RIftnHerI Resins, The first batch of vinyl ester resin Swancorp 980 (denoted as 
Swancorp 980 (a)) was tested for toughness and resin tensile modulus. A value of 1840 
(J/m2) for Gic test (b) and 1.61 GPafor resin modulus was obtained for this first batch. 
Wind turbine blades require resin systems with a resin tensile modulus of at least 2.75 
GPa. Turbine blades may not require the high toughness of the Swancorp 980, which 
made this system an extremely tough resin candidate but with low modulus. TECTRA 
Inc., manufacturer of the Swancorp vinyl ester series, suggested blending the Swancorp 
980 resin with a compatible system, Swancorp 901, a non-toughened vinyl ester resin, as 
an alternative to increase the resin modulus relative to Swancorp 980 while providing a 
moderate toughness. The motivation for this blend was to study the effects of toughness 
and resin modulus when blending compatible resins. The amount of rubber in a 
toughened resin is related to the toughness of the system [25]. Toughness can be 
decreased and the resin modulus increased by diluting the amount of rubber in such resin, 
by mixing it with a non-toughened resin [31].
A second batch of resins was received, Swancorp 980 (b) and Swancorp 901. 
They were blended and cured as described in Table 3.1. Gic and tensile modulus results 
for the resin blend are shown in Table 4.7 . It is shown in this Table that Swancorp 980 
(b) resin had a much lower Gic value and a higher resin tensile modulus than the initial 
Swancorp 980 (a). Swancorp 901 had only a slightly higher resin modulus than 980 (b), 
therefore the modulus did not change much for the blend. Modulus changes could 
probably be better observed if 980 batch (b) was similar to (a). The cause of the
50
difference between batches received is unknown. Toughness changed as expected for the 
blends [32]. Difficulties with consistency of the Swancorp vinyl ester resins led to a focus 
on Derakane vinyl esters.
( '
Table 4.7 Comparison of Gic and E Modulus for different Swancorp resins and blend.
Resin Neat resin Gic (b) Overall Gic Specimens
E Modulus J/m2 J/m2 . tested
, GPa
Swancorp 980 (a) 1.63 1840 1923 4
(0.02)* (161) : (94)
Swancorp 980 (b) 3.05 852 809 3
(0.04) (215) (104)
Swancorp 980 (b) & 901 2.76 569 635 3 ,
(0.06) (23) (46)
Swancorp 901 3.37 ■208 289 3
(0.07) (20) (24)
*(Std. Deviation)
Effects of Fabric Architecture on Gjr-Most Gic values were determined using the 
D155 stitched unidirectional fabric, but several tests were also run for comparison in a 
bonded unidirectional fabric with a thin veil backing. Gjc values were determined for the 
UC1018/V bonded fabrics (Appendix) to be greater placing the fabrics back to back (veil 
to veil) at the mid-plane in the DCB specimens as shown in Figure 4.5.
51
DCB results for [0]6 using D155 and UC1018/V fabrics 
with CoRezyn 63-AX-051 resin
nuci 018A/fabrics
300 
' f  250 
^  200 
I  150
I  100
(5 50
0
DI55 fabric PoIyesterVeiI Glass Veil veil- PoIyesterVeiI 
veil-veil veil glass-glass
—
.
Figure 4.5 Comparison of Gic test (b) values using different fabrics.
Baseline D155 fabrics had similar Gic values to UClOl 8/V fabrics when the 
fibers were arranged glass to glass at the mid-plane. Overall, fabric type had little effect 
on Gic for this limited comparison.
Results for T-Stiffener Specimens
The !-Stiffener pull off test gives a measure of structural integrity in a 
delamination sensitive geometry (Figure 2.9) [24]. Two non-toughened resin systems and 
five toughened systems were compared. Maximum load, initial damage load and the 
displacement at the maximum load are shown on Table 4.8. Displacement at initial 
damage load and thickness of skin plus the thickness of flange are given in the Appendix. 
Typical load - displacement curves are compared in Figure 4.6.
52
Table 4.8 Results for T-Stiffener Pull off Tests.
Resin
Initial
Damage
Load
N/cm
Maximum
Load
N/cm
Displacement 
at maximum 
Load 
cm
Specimens
tested
CoRezyn 
63-AX-051
87
(5.57)*
135
(6.03)
0.68
(0.06)
3
PET-P460 120 164 0.84 I
Swancorp 980 
(batch a)
119
(9.29)
182
(6.03)
1.35
(0.18)
4
Derakane 8084 144 194 0.90 2
System 41 168 209 0.67 2
SC-14 132 192 1.91 2
Poly 15-D65 141 262 1.16 I
*(Std. Deviation)
SC-14
Derakane 
8084 ,
■p 200
S- 150
J  100
Epoxy 
Svstem 4 1
Polyester 
63-AX-051
Displacement (cm)
Figure 4.6 Load -  displacement curves for T-Specimens
Polyester resin 63-AX-051 and the toughened PET P460 had the lowest 
maximum loads and low ultimate displacements. The polyurethane Polyl5-D65 in fact
53 -
had the highest maximum load but its ultimate displacement was similar to the polyester 
resins. Initial damage load and displacement at initial damage are recorded at the onset 
of non-linearity on the load displacement curve for a T-Pull of test (Figure 2.10). 
Delamination growth as crack propagation in the specimen can be seen when the initial 
damage load is reached. One of the reasons for recording this load is to compare resin - 
effects when a wind ,turbine blade is going to develop cracks and delamination in skin 
stiffened regions. System 41 had the highest initial load of all resins.
The specimens differed significantly in thickness for various resins. Thinner 
specimens fail at lower loads and higher displacements for the same toughness 
(Appendix). A combination of high maximum load and high displacement at maximum 
load provide the toughest system. Delamination failure could be seen for polyester 
resins, epoxy System 41 and vinyl ester resin Derakane 8084. The difference between 
them is that CoRezyn 63-AX-051 and Derakane 8084 experienced a total delamination 
between skin and flange. System 41 and PET P460 resins also experienced delamination 
but the flange was still attached to the skin after the composite failure. System 41 and a 
. Derakane 8084 specimens can be seen in Figure 4.7.
54
Figure 4.7 Derakane 8084 and System 41 T-Specimens.
The toughened resins epoxy SC-14, vinyl ester Swancorp 980 (a), and the 
polyurethane Poly 15-D65 experienced a compression failure prior to delamination. 
These systems experienced no delamination between skin and flange. Swancorp 980 and 
SC-14 resins behave similarly in the way that noisy cracks were formed on the web 
region, but the polyurethane cracks were not heard due to its rubbery state and high 
damping. Shown in Figure 4.8 is an SC-14 T specimen, which shows the failure line at 
the bottom of the skin generated by the compression failure.
55
Compressive
failure
Figure 4.8 Epoxy SC-14 T-Specimen.
Figure 4.9 shows a comparison between maximum load for T-specimens and 
One. Mode II energy release values and maximum load for T-Specimens correlate for the 
different resins as shown on Figure 4.9. This is probably due to the nature of the loads 
during ENF and T-Pull off testing. Pull-off testing is a mixed mode (between modes I 
and II) dominated test [24]. The high performance of the non-toughened epoxy System 
41 for mode II and T-Pull off tests is again evident.
56
if
If
s  ^
300 
— 250
200
150
100 
50 -
CoRezyn
63-AX-051
__®
Derakane
808^
Epoxy System 41
...............•—
----mSwancorp 
980 (a)
•  Non-toughened resins 
■ Toughened resins
1000 2000 3000 4000
Cue (J/m2)
Figure 4.9 Comparison between Maximum load for Stiffener Pull off Tests and Gnc.
Transverse Strength
The ultimate transverse strength (UTS) of a composite is dominated by the resin 
matrix. A layup of [0/+45/0]s was used with D155/DB120 fabrics. Tests were conducted 
by loading in the 90° direction, so that the dominant ply stresses were transverse tension 
in the 0 0 plies and shear and transverse tension dominated in the +45 plies [24]. Results 
for different resins are shown in Table 4.9. Tensile results for Derakane vinyl ester resins 
using different fiber contents are shown in Table 4.10. Stress -  strain diagrams for the 
resins studied can be seen in the Appendix. Figure 4.10 gives a typical stress-strain
curves for different materials.
57
N
Table 4.9 Tensile results for [0/+45/0]s composite using different resins. Three specimens 
were tested for each resin. Vfis the fiber volume in %.
Resin , UTS
MPa
Knee stress 
MPa
Tensile E , 
GPa
Maximum 
% strain
CoRezyn 63-AX-051 73.75 29.47 10.42 2.97
37% Vf (4.06) (0.61) (0.23) (0.52)
Swancorp 980 (batch a) 107.40 52.10 6.91 3.81
36% Vf (2.12) (2.72) (0.19) (0.07)
Poly 15-D65 107.80 38.47 5.56 4.54 ■
39% Vf (13.03 (1.02) (0.07) , (0.79)
System 41 113.70 60.47 11.63 3.39 .
42% Vf (6.00) (0.33) (0.11) (0.32)
SC-14 111.28 60.53 9.41 3.80
38% Vf (6.91) (0.97) (0.07) (0.67)
*(Std. Deviation)
Table 4.10 Tensile results for [0/+45/0]s composite using Derakane vinyl ester resins. 
Three specimens were tested for each fiber volume (Vf).
Resin UTS
MPa
Knee stress 
MPa
Tensile E 
GPa
Maximum 
% strain
Derakane 411C-50 56.32 36.20 9.31 4.44
39% Vf (1.17) ' (0.57) (0.09) (0J7) '
Derakane 411C-50 59.11 46.37 8.22 3.94
35% Vf (0.56) (2.25) , (0.20) i ' (0.32)
Derakane 8084. 65.09 43.50 9.11 4,49 .
39% Vf : (1.66) (1.19) (0.41) (0.43)
Derakane 8084 62.97 44.16 8.35 4.10
35% Vf (0.24) (0.78) (0.21) (0.29)
*(Std. Deviation)
58
Epoxy
SC-14120 i
Polyurethane 
Polv 15-D652: 100 Polyester 
63-AX-051 Vinyl ester 
, 8084
«  60  -
Strain (%)
Figure 4.10 Stress-strain diagram for [0/±45/0]s composite with different resins.
Knee stresses were determined by a 0.2% strain offset technique described earlier. 
Knee stress is a more meaningful value than the ultimate tensile stress for a composite 
with no O0 fibers. The knee stress occurs when the composite starts to matrix crack, while 
the UTS is recorded when the composite has failed. With no O0 fibers, the knee stress is 
the limiting practical value for design [34]. Epoxy resins, System 41 and SC-14 had the 
highest knee stresses, twice as high as the Polyester 63-AX-051 which had the lowest 
knee stress of all the resins tested. Toughened vinyl esters Derakane 8084 and Swancorp 
980 (a) had the second highest knee stresses. The polyurethane Poly 15-D65 had similar 
knee stresses to the untoughened Derakane 411C-50, apparently due to the low yield 
stress of the rubbery urethane matrix.
Toughened materials and the non toughened Derakane 411C-50 had higher tensile
59
strain to failure than the CoRezyn. The polyurethane Poly 15-D65 had the highest 
transverse ultimate strength. The results show that toughened resins are more likely to 
have a lower transverse modulus but a higher UTS. Non-toughened and stiff resins such 
as CoRezyn 63-AX-051 and System 41 had higher transverse modulus than toughened 
thermosets. Epoxy SC-14 had the highest transverse modulus for a toughened resin. 
Most toughened resins show higher UTS than their non toughened base resin. High 
performance was observed in epoxy resins, with high transverse modulus, knee stresses 
and UTS. Delamination was observed on several sites in Polyester 63-AX-051 
specimens, and some delamination was observed in Derakane 8084 and Epoxy SC-14 
around the failure crack (Figure 4.11).
Figure 4.11 Tension specimens tested in the 90° direction.
60
Transverse tests on unidirectional [0]6 and (+45/-45)3 were carried out by 
Samborsky [35]. The transverse modulus for unidirectional specimens was predicted 
earlier in Equation 2.2. Experimental and predicted results can be seen on Figure 4.12.
9 i
% 4 - 
E 3
°o 2 
2L 1
O - -
2.7
Epoxy SC-14
I
2.8 2.9
Vinylester
411C-50 Vinylester
• g 8084
Fblyesterl ■
63-AX-051
#  Bcperimental values. 
■ Redicted values.
3 3.1 3.2 3.3
Tensile modulus of neat resin (GPa)
Figure 4.12 Experimental vs. predicted 90° Modulus for [OJs composite.
Predicted results were found using Equations 2.3. Good agreement with the 
experimental values can be seen. This indicates that, as predicted, the neat resin modulus 
dominates the composite transverse modulus.
A layup of [0]6 was tested for resins: polyester 63-AX-051, vinyl esters 411C-50 
and 8084 and epoxy Sc-14, while a layup of [±45]s was tested on polyester 63-AX-051 
and vinyl ester 8084 [35]. Tests were conducted by loading in tension transverse to the 
fibers in the 90° specimens, and the results are compared to the [0/+45/0]s test results. 
Results and comparisons for the 90 0 tensile modulus and the 90 0 knee stress are shown 
on Figures 4.13 and 4.14 respectively.
61
20
18
— 16 (0
Polyester Vinylester Vinylester Epoxy
63-AX-051 411C-50 8084 SC-14
a  E for neat resin
■ [0/+_45/0]s 
DB120/D155
□ [+_45]6 Dl 55
Figure 4.13 Modulus E, for neat resin and composites tested at 90° in tension.
Figure 4.14 Knee stress for neat resin and composites tested at 90° in tension.
Similar moduli for the neat resin are observed in the four systems. Polyester had 
the highest transverse modulus for the [0/+45/0]s layup. Derakanes 411C-50, 8084 and 
the epoxy SC-14 showed similar transverse modulus with a [0/+45/0]s layup. Vinyl ester
62
411C-50 had the highest transverse modulus for a (±45)3 layup, followed by the CoRezyn 
63-AX-051. The epoxy SC-14 had the lowest transverse modulus for a (±45)3 layup.
Derakane 8084 had the highest yield stress values for a neat resin, while epoxy 
SC-14 had the highest value for knee stress in [0/±45/0]s layups. The polyester had the 
lowest knee stresses for neat resin and for [0/±45/0]s composites. Derakane 411C-50 had 
the highest knee stresses and resin modulus for the (±45)3 laminates.
Compressive Strength
Compressive strength in the O0 direction is a critical property for wind turbine ' 
blades and is also a matrix dominated property [15]. Compressive strength results for the 
[0/+45/0]s composite loaded in the O0 direction are compared with 90° tensile knee stress 
and neat resin modulus for different resins in Table 4.11 and for different fiber volumes 
(Vf) using Derakane vinyl ester resins in Table 4.12.
Table 4.11 Results for [0/+45/0]s composite using different resins. Three specimens were 
tested for each type of resin.
Resin Compressive 
O0 Strength 
MPa
Tensile 90° 
knee stress 
MPa
Neat resin E 
GPa
CoRezyn 63-AX-051 517.39 29.47 3.18
36% Vf (29.24)* (0.61) (0.12)
Swancorp 980 (batch a) 420.37 . 52.10 1.63
36% Vf (25.17) (2.72) (0.02)
Poly 15-D65 378.93 . 38.47
39% Vf (24.25) . (1.02)
System 41 567.80 60.47 3.57
39% Vf (44.85) (0.33) . (0.06)
SC-14 531.64 60.53 2.80
37% Vf (10.71) (0.97) (0.03)
*(Std. Deviation)
63
Table 4.12 Results for [0/+45/0]s composite using Derakane vinyl ester resins. Three 
specimens were tested for different fiber volumes (Vf).
Resin Compressive
Strength
MPa
Tensile 90° 
Knee stress 
MPa
Neat resin E 
GPa
Derakane 411C-50 451.36 36.20 3.21
39% Vf (16.17) (0.57) (0.04)
Derakane 411C-50 572.39 46.37
35% Vf (21.19) (2.25)
Derakane 8084 461.60 . 43.50 3.25
39% Vf (11.92) (1.19) (0.15)
Derakane 8084 541.45 44.16
35% Vf (39.21) (0.78)
As predicted by Eq. (2.3), higher neat resin modulus correlates with higher 
compressive strength. Rubbery polyurethane and Swancorp 980 (a) showed the lowest 
compressive strengths. The Derakane resins processed in different molds with different 
fiber contents show significant differences in compressive strength which are not 
understood at this time. The higher values at 35% fiber are probably more representative, 
with some unknown problem evident in the 39% tests. Compressive strength should not 
be that sensitive to fiber content [14]. The matrix plays an important role in compressive 
failure. As discussed earlier, a compressive load can not be supported by the fibers 
themselves. Figure 4.15 Compares experimental compressive strength with predictions 
from Eq. 2.3. In both results, experimental and predicted, it was found that increases in 
modulus of the resin corresponded to increases in compressive strength of the composite. 
Predicted values were a factor of 3.5 higher than the experimental results. This model, 
which assumes perfectly straight fibers is expected to provide a high estimate of 
compressive strength by a factor of 2 to 4 [14]. Since the prediction does not include ± 45
64
layers, it is expected to be further increased relative to the laminate tested.
1. Vinylester 411C-50
2500 2. Polyester 63-AX-051 a  Predicted values
£ 3. Epoxy System 41 ■ Experimental values
C 2000 4. Vinylester 980(a)
S 5. Epoxy SC-14</>
1500
6. Vinylester 8084 A
. 1 1
I * 1000 ^ ▲o.
E
5 500 -
4
■
5 1
O
0 - ___________,__________ ,________
0 0.5 1 1.5 2 2.5 3 3.5 4
Tensile modulus of neat resin (GPa)
Figure 4.15 Experimental values for [0/+45/0]s versus predicted compressive 
strength for the O0 layers alone.
Toughness vs. Other Mechanical Properties
It is accepted that the toughening of a resin usually degrades its yield strength, 
modulus and Tg [5,7,20,26]. It is shown in Figure 4.16 that increases in Gic of a resin are 
associated with decreases in the composite transverse modulus, which is dominated by 
matrix modulus. Figures 4.17 compares Gic test (b) values and O0 compressive strength 
of [0/±45/0]s laminates. Again reflecting matrix modulus effects, increases in G,c for the 
tested thermoset resins correlate to moderate decreases in compressive strength. Current 
results indicate that interlaminar fracture toughness increases at the expense of some 
mechanical properties. However, as noted earlier, the 90° tensile knee stress is generally 
increased by toughening the resin. Finally, the main reason for toughening the resin is to 
increase the structural integrity, and T-section pull off tests in Figure 4.9 demonstrate a 
significant improvement for toughened resins with the exception of untoughened System
65
41, which inherently has a high Gnc-
-m 10 
CL
£  8
=J
I 6
E 4
s  ,
CoRezyn
63-AX-051
System  ^ s c . ^
Tterakane 
8084
411050
•  Non-toughened resins 
■ Toughened resins
Swancorp
980(a)
500 1000 1500 2000
Gic test (b) (J/m2)
2500
Figure 4.16 90° Modulus vs. Gic for [0/±45/0]s composite.
700 i
„ ~ 6 0 0
% I  500P 2
2 T  400
Q. *5
E Ot3Oo
Ii-O
100
0
3
a Neat non-toughened Resins
1. Polyester 63-AX-051
2. Epoxy System 41
3. Vinylester 411050
4. Poly 15-065
0 500 1000
7
Toughened resins
5. Derakane 8084
6. Epoxy 5014
7. Swancorp 980 (a)
1500 2000
Gic test (b) (J/m2)
2500
Poly 15-D65
3000
4
3000
Figure 4.17 O0 Compressive strength vs. Gic for [0/+45/0]s composite.
66
Moisture Effects on Mechanical Properties
Earlier results showed that the toughened vinyl esters decrease slightly in heat 
deflection temperature relative to untoughened vinyl esters. [0/±45/0]s composite 
specimens were also soaked in water for 330 hours at a temperature of 50 °C and tested at 
20°C while still wet.. Transverse tension and 0° compression tests were performed on 
specimens before and after water exposure. Results for 90° modulus, 90° tension, 
0°compression and 90° knee stress are shown in Figures 4.18, to 4.21 respectively. 
Polyester resin CoRezyn 63-AX-051 had ,a decrease of 15 % in its 90° modulus and 
0°compressive strength, while the 90° tensile strength was unaffected (it should be noted 
that longer term conditioning has produced more significant reductions for this resin 
[35]). Swancorp 980 (a) resin was less moisture sensitive, with decreases of around 5 % 
in its 90° modulus and tensile strength; its O°compressive strength was unaffected.
The polyurethane Poly 15-D65 was the most moisture sensitive resin. It had a 
decrease of almost 50% in its 90° modulus while its 90° tensile and 0° compressive 
strengths decreased 26 and 29%, respectively. Tg for Poly 15-D65 (and most urethanes) is 
below 0 °C, which reduces the performance at room and elevated temperatures. For the 
epoxy System 41, the 90° modulus and 90° tension strength values decreased 12%, while 
O°compressive strength decreased 5%.
67
The polyurethane resin mechanical properties decreased almost 10 times more 
than did those of the vinyl ester resin. Overall, Swancorp 980 is the least moisture 
sensitive resin. Epoxy and polyester resins behave similarly. Their mechanical properties 
were decreased three times more than for the Swancorp 980, when subjected to moist 
conditions. (More extensive hot/wet results for many of the resins tested in this study can 
be found in Reference [13]). Knee stresses were hot significantly reduced for most resins, 
except for the Poly 15-D65, which had a reduction of around a 30% in the knee stress 
after water absorption.
Polyester 63- Vinylester 980 Polyurethane Epoxy System 
AX-051 15-D65- 41
□  Dry □  After 330 hrs at 50 0C
iv
Figure 4.18 90° Modulus for wet and dry [0/f45/0]s composite tested at 
room temperature.
'O ’
68
120 -
£
WJ IUU "
2? OfY _
, ' ’
Io «■ 80
"I| i ”: Hi
- 1K
■M
, - J i
S  40
O 20 -
O) ; •
U H
Polyester 63-AX- Vinylester 980 Polyurethane 15- Epoxy System 41
Q  Dry
051 D65
C3 After 330 hrs at 50 0C
Figure 4.19 90° tensile strength for wet and dry [0/+45/0]s composite 
tested at room temperature.
> «  400
J= 100
Polyester 63- Vinylester 980 Polyurethane Epoxy System - 
AX-051 15-D65 41
O  After 330 hrs at 50 0CO  Dry *
Figure 4.20 O0 Compressive strength for wet and dry [0/±45/0]s 
composite tested at room temperature.
69
^  120 i
□  After 330 hrs at 50 0C□  Dry
Figure 4.21 90° Knee stress for wet and dry [0/±45/0]s composite tested 
at room temperature.
Water Absorption
Water absorption was measured on cured pure resin specimens and composite. 
Results for water absorption of pure resin and composite for specimens soaked for 300 
hours at 50 0C are shown on Table 4.13. Vinyl ester resins absorbed less water for neat 
resin and composites, followed by the polyester resin. Derakane 8084 absorbed 25 % 
less water for neat resin and 13 % less for the composite than did polyester. Swancorp 
980 absorbed 64 % less water for neat resin and 56% less for the composite than the
polyester.
(Table 4.13 Water absorption (% weight gain) for and average of 3 specimens of neat 
resin and [0/+45/0]s composite specimens.
Resin Neat resin Composite
(% weight ,gain) (% weight gain)
Polyester
CoRezyn 63-AX-051 1.41 0.47
Vinyl esters 
Derakane 411C-50 0.84 *0.35 ■
Derakane 8084 1.06 *0.41
Swahcorp 980 0.51 0.21
Epoxies 
System 41 2.51 ' 0.83
**SC-14 1.85 1.22
Polyurethane 
Poly 15-D65 2.25 0.87
(*) Tests performed by Li [13] on [0]6 composite specimens.
Epoxy resin System 41 absorbed the highest amount of,water for neat resin, 77% 
more water than for the polyester, and Epoxy SC-14 absorbed the most water for a 
composite, 159 % more water than for the polyester. Polyurethane 15-D65 resin is also 
very moisture sensitive, it absorbed 60% more water for the neat resin and 85% more 
water for the composite than did the polyester. The polyurethane resin absorbed similar 
amounts of water to the epoxy resins, but its mechanical properties were decreased much 
more after water absorption, apparently due to low Tg values.
Resin Pricing and Overall Comparisons
Resin Pricing
Prices of resins vary greatly and a comparison is given here for vendor quotes for 
40,000 lb lots in Spring, 1999. Price comparison between different polyester, vinyl ester 
and epoxy resins is shown in Figure 4.22. Polyester resins have the lowest prices of the 
resins used, while vinyl ester and the urethane prices are in between epoxies and 
polyester resins. Epoxy resins had similar prices and also the highest prices of all the 
resins tested. System Three and Applied Poleramic companies use non-toughened 
epoxies from Dow Chemical and Shell as the resin base for their products. Additives to 
increase mechanical properties are included in the resin which increases the price of the 
epoxy base resin from average prices of 1.75 $/lb to an average of 2.8 $/lb. Different 
prices can be seen for the non toughened Derakane resin 411C-50 and the rubber 
modified Derakane 8084, the second one being more expensive because of its additive
content to increase toughness performance.
Price comparisson for different resins for a 55 gallon drum
base
1. Corezyn 63-AX-051
2. PET P460
3. Arotran Q6038
4. Derakane 411C-50
5. Derakane 8084
6. Swancorp 980
7. System 41
8. SC-12
9. SC-14
10. Polytek 15-D-65
u  1 2 3  4 5 6 7 8 9  10
■  Non-toughened resins D  Toughened resins
Figure 4.22 Resin prices for a 40,000 lbs estimation.
72
Overall Comparisons
Figures 4.23 to 4.26 show prices and mechanical property comparisons of the 
baseline polyester CoRezyn 63-AX-051 with the other polyesters, vinyl esters, epoxies 
and polyurethanes, respectively. Price and results for each mechanical test were divided 
by the CoRezyn values in order to compare them. It is shown on Figure 4.23 that the 
other two polyester resins had higher Gic values than the base polyester. Gne values were 
almost twice as high for the PET P460 but the Arotran Q6038 Gnc values were almost 
four times lower than for the baseline polyester resin. Derakane vinyl ester 411C-5Q has a 
higher cost compared to polyester prices. It costs 50 cents per pound more than the 
CoRezyn but it was twice as tough in both delamination modes. Derakane 8084 costs 
one dollar per pound more than the polyester but is almost four times tougher. Swancorp 
980 rubber modified vinyl ester resin is more than 2.5 times more costly than CoRezyn 
but is also more than 11 times tougher. Its Gnc values were not very high compared to the 
Derakane values but at least 3 times higher than the CoRezyn. (Figure 4.24)
Epoxy resin results compared with CoRezyn are displayed on Figure 4.25. Prices 
for epoxy resins were almost three times higher than the CoRezyn. System 41 epoxy 
rosin did not show a significant increase in Gic compared with the CoRezyn but its Gnc 
value and T-pull off resistance were the highest of all resins. Epoxy SC-14 had the 
highest Gic value for epoxy resins, four times higher than for the CoRezyn. System 41 
and SC-14 epoxies had similar compressive strengths with a higher knee stresses than the
CoRezyn.
73
The CoRezyn polyester has a low toughness compared to the other resins tested, 
but it offered similar compressive strength to most resins at a very reasonable price. The 
polyurethane Poly 15-D65 had a superior toughness compared with all resins used at a 
relatively low price with a Gic value seventeen times greater than the CoRezyn, but its 0° 
compressive strength and 90° composite modulus were the lowest of all resins (Figure 
4.15). Its Ghc value could not be determined because the specimen failed in 
compression, and the value given in the results is an estimate of Gnc using the maximum 
compressive load. The urethane has too low of a compressive strength for use in wind 
turbine blades (Figure 4.26).
Figure 4.23 Comparison between polyester resins studied and the CoRezyn 
63-AX-051 whose values are in ().
74
□ Price (0.93 dls/lb) BGIc (159 J/mA2)
■ Gllc: (977 J/mA2) ■ Knee stress (29 MPa)
■ Compressive Strength ( 517 MPa)
c6
Figure 4.24 Comparison between vinyl ester resins studied and the 
CoRezyn 63-AX-051, whose values are in (). Derakane compressive 
strength are for the 35 % fiber batch.
□ Price (0.93 dls/lb) ■ Glc (159 J/mA2)
H Gllc: (977 JZ(TIaZ) ■  Knee stress (29 MPa)
H Compressive Strength ( 517 MPa)
Figure 4.25 Comparison between epoxy resins studied and the CoRezyn 63- 
AX-051 whose values are in ().
□ price (0.93 dls/lb) mGk (159 JZnYXZ)
B  Gllc: (977 J/rrY'2) ■ Knee stress (29 MPa)
■ Compressive Strength ( 517 MPa)
Poly 15-D65
Figure 4.26 Comparison between urethane resin studied and the CoRezyn 
63-AX-051 whose values are in ().
Processing Observations
The polyester and vinyl ester resins tested had similar low viscosities (100 to 200 
cp) which made them relatively easy to process by RTM and to wet out fibers by 
injecting at moderate speeds. The epoxy resins had higher viscosities, on the order of 500 
cp, which requires lower speed injection to decrease the probability of void formation 
and fiber wash out. The polyurethane resin had the lowest viscosity (50 to 80 cp), which 
made it easy to inject, but a disadvantage was that it developed porosity while curing. 
Anti-porosity forming agents are available for Poly 15 polyurethane series, which were 
not used because they can potentially accelerate the already rapid curing process and 
reduce the available injection time. For this study, most of vinyl ester resins needed to be 
promoted as discussed in Chapter 3 which is not very convenient since the user is
exposed to promoter chemicals. These can be supplied in promoted form if required as 
was one Derakane 8084 batch. It is important to add the proper amount of promoter, 
CoNap5 according to the amount of Trigonox catalyst to be used (Table 3.1). Ifthis is not 
followed, improper curing may result.
Vinyl ester resins, especially Swancorp 980, shrink more than any other resin 
cured. Molded parts such as flat plates experienced a slight deflection, therefore it is 
recommended to de-mold them before applying heat to post-cure them. Combined 
stresses generated on the mold glass plate by the shrinkage and thermal expansion 
coefficient differences relative to the glass represent a potential risk of breaking the mold 
glass (this is a special problem for the molds used in this study). Toughened epoxy resins 
required the most time to cure. System 41 required from 15 to 20 hours to cure but Epoxy 
resins SC-12 and SC-14 required at least 3 days at room temperature to start gelling. For 
these two epoxies the better way to cure them was by heating from 3 to 4 hours at 60 C 
to accelerate the curing process. Higher temperatures will degrade gaskets and cause 
thermal expansion problems. Once heat is applied to the resin, the plate can then be 
demolded and postcured following the resin curing cycles (Chapter 3). It is recommended 
to apply mold release agent on the rubber gaskets used for SC-12 and SC-14 epoxies 
since they bond to the gasket when curing. Mold release agents for each resin work better 
when applied six hours or more in advance of molding.
77
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
Several potential wind turbine blade resins differing in properties and cost have 
been evaluated in terms of their effects on composite laminate delamination resistance, 
matrix dominated mechanical properties, integrity of skin/stiffener substructure, 
environmental resistance and processing characteristics. Relative to the baseline polyester 
resin, most resins showed improved delamination resistance and transverse composite 
strength properties, while maintaining the desired level of compression strength and 
modulus. Several resins also showed improved temperature and moisture resistance. Two 
of the toughest resins, a toughened vinyl ester and a urethane, did not have the requisite 
modulus and temperature resistance for the wind turbine blade application. However, 
several resins did provide significantly improved properties over the baseline polyester at 
moderate increases in cost.
In general, the orthophthalic polyesters showed lower cost, the lowest toughness 
and structural integrity, and low temperature resistance with significant moisture 
sensitivity. The primary mechanical properties of the polyesters were adequate for wind 
turbine blades at moderate temperatures. The vinyl esters provided significant
improvements in toughness, increased temperature and moisture resistance and adequate 
strength and modulus properties, thus providing a compromise in properties and cost. 
Epoxy resins showed the best strength and toughness properties and improved 
temperature resistance, but were sensitive to moisture and had the highest costs and 
processing difficulties. The urethane was very tough, but did not have adequate modulus, 
temperature or moisture resistance.
The effects of changes in matrix stress-strain properties on composite properties 
followed expected trends. More ductile resins provided greater delamination resistance 
and structural integrity in the composites. Reductions in matrix modulus resulted in 
reduced composite modulus in the transverse direction as well as reduced compressive 
strength in the fiber direction. Resins with the greatest ductility also showed significant 
reductions in modulus and temperature resistance, including cases where relatively brittle 
base resins were modified to increase toughness. Modified resins were also more costly 
than unmodified resins. Resin moisture sensitivity correlated with composite moisture 
sensitivity. Non-toughened vinyl ester and epoxy resins showed significant improvements 
in mode II toughness over the baseline polyester, which also improved the structural 
integrity of skin-stiffened sections.
In terms of the best way to screen matrix materials, the results of this study lead to 
several conclusions. Ifthe neat resin can be tested, the stress-strain, heat deflection 
temperature, and moisture sensitivity data correlate well with the various composite 
properties determined in this study, as noted in each section. Critical composite tests are 
Gic and Gnc and compressive strength. The structural integrity of the stiffened skin
79
section correlated well with Gjio- Knee stress in an off-axis tension test is a good 
indicator of matrix modulus (if not available) and general off-axis, matrix dominated 
tensile strength properties (which depend on matrix strength, ductility, and bonding to 
fibers). Off-axis tests such as +45° are more convenient to run than are 90° tests on 
unidirectional materials.
Specific conclusions for each type of resin are as follows:
1. Polyester Resins. The baseline resin, CoRezyn 63-AX-051, was brittle, resulting 
in poor delamination resistance, low transverse knee stress, and poor structural 
integrity. However, its elastic modulus was high enough to provide adequate 
compressive strength. The temperature resistance was not sufficient for many 
applications and it was moisture sensitive. Relative to the baseline resin, the polyester 
PET P460 showed slight increases in mode I toughness, and greater increases in mode 
II toughness and skin-stiffener maximum loads at a lower price than the CoRezyn. 
The polyester Arotran Q6038 showed significant increases in mode I, toughness but 
its mode II toughness was much lower than the baseline polyester. Other 
disadvantages of the Arotran Q6038 where it higher cost and its high exothermic 
reaction while curing, which caused some processing difficulties.
2. Vinyl ester Resins. Swancorp and Derakane vinyl ester resins showed 
improvements in toughness, especially the toughened versions. Swancorp 980 batch 
(a) had a much higher toughness in mode I and the highest tensile knee stress for 
vinyl ester resins, but a lower modulus than is acceptable for wind turbine blades. 
This resin also showed significantly different results for mode I toughness and resin
80
modulus in a later batch (b). Resin toughness was increased in the brittle Swancorp 
901 base resin by mixing it with the 980 batch (b) resin with minor changes in resin 
modulus. For Derakane resins, the 8084 showed a higher value for mode I toughness 
than the 411C-50, but they had similar modulus, mode II toughness, knee stress and 
compressive strength values, all higher than the baseline polyester. Costs for 
Derakane resins were moderately higher than for the baseline polyester. It is not clear 
whether the added cost of 8084 over 411C-50 is warranted considering the small 
improvement in properties. Some tests including skin-stiffener integrity were not run 
for the 411C-50. All vinyl ester resins showed a good resistance to moisture effects, 
with the Swancorp 980 the least moisture- sensitive. Their room temperature 
mechanical properties remained almost constant after water absorption for 330 hours 
at 50°C. Heat deflection temperature was improved for Derakane resins over the
baseline polyester. /
3. Epoxy Resins. Non toughened System 41 showed a stiff but brittle behavior. Its
mode I toughness value was not significantly higher than for the baseline polyester, 
but it had the highest mode II toughness and initial damage load in skin-stiffener 
tests of all the resins tested. Its tensile knee stress and compressive strength were 
similar to those for the toughened SC-14 resin, which had a much higher mode I 
toughness. The toughened SC-12 resin had lower mode I and II toughness values than 
SC-14 resin, similar to the non-toughened 411C-50 vinyl ester, but significantly 
higher than the baseline polyester. Batch SC epoxy resins showed a stiff and tough 
behavior. Epoxy resin System 41 absorbed the most percent weight of water, but its
mechanical properties were not substantially reduced after water exposure as they 
were for other resins. Epoxy SC-14 had the highest water absorption value for 
composites.
4. Polyurethane. The polyurethane Poly 15-D65 showed a very ductile behavior. It 
had the highest mode I toughness and maximum load for skin-stiffener specimens, 
but the lowest composite modulus and compressive strength. Its price is significantly 
higher than for the polyester, and it was the most environmentally sensitive resin. Its 
mechanical properties were greatly reduced after water exposure. This resin is not 
appropriate for wind turbine blades.
\
R ecommendations
Polyester resins are commonly less costly, so it is recommended to seek other 
toughened unsaturated orthophthalic polyesters with increased moisture and temperature , 
resistance at moderate cost and to study isophthalic polyesters which are known for 
increased mechanical, thermal, and environmental properties. Other non-toughened vinyl 
ester resins and blends of Derakanes 411C-50 and 8084 should also be considered due to 
their reasonable cost, good properties arid low environmental sensitivity. It is also 
recommended to explore neat epoxy resins with lower prices and no additives included to 
compare their mechanical performance with the baseline polyester. Thermoplastic resins 
might be added to the list if manufacturing methods which allow high resin viscosity are 
considered. The comparison of different resins in this study might be affected by the
82
general purpose coupling agent used with the reinforcement. Specific coupling agents for, 
say, vinyl ester resins might provide improved transverse strength and structural integrity.
Resins which have received favorable ratings in the screening tests used in this 
study should be subjected to more intensive testing. The vinyl esters such as Derakane 
411C-50 and 8084 appear to be strong candidates for wind turbine blades. They should 
be tested more intensively, including elevated temperature testing, fatigue under various 
loading conditions, and performance in substructural elements like beams as well as 
small blades. Only then can the full potential as a replacement for the baseline polyester 
be judged. It is possible that improved properties could reduce blade weight, more than 
offsetting the increased resin costs.
83
REFERENCES CITED
1. Mandell, J.F., Samborsky, D.D., “DOE/MSU Composite Material Fatigue Database: 
Test Methods, Materials, and Analysis,” Sandia National Laboratories Contractor 
Report, SAND97-3002. December 1997.
2. Hunston, D.L., Johnston, N.J., “Matrix Resin Effects in Composite Delamination: 
Mode I Fracture Aspects,” Toughened Composites, ASTM STP 937, American Society 
for Testing and Materials, Philadelphia, 1987, pp. 74-114.
3. Volume II, “Engineered Plastics,” ASM International, Engineered Materials 
Handbook, November 1988, pp. 240-292.
4. Valenti M “Resin transfer molding speeds composite making”, Mechanical 
Engineering - CIME, November 1992, Vol. 114, No. 11, pp. 46-49.
5. Astrom, B.T., “Manufacturing of Polymer Composites,” Department o f Aeronautics, 
Royal Insitute o f Technology, Chapman & Hall, 1997, pp. 1-175.
6. White, D.W., Puckett, P.M., “Resin Systems and Applications for Resin Transfer 
Molding” The Dow Chemical company US.A, Freeport, Texas, pp. 1-5.
7. Kinloch, A.J., Young, R.J. “Fracture Behaviour of Polymers,” Elsevier Applied 
Science Publishers, 1988, pp. 1-181.
8. Li, M., “Environmental Effects on Composites Materials,” Master’s Thesis in 
Chemical Engineering, Montana State Uniyersity-Bozeman, to be published.
9. Turi, E.A. “Thermal Characterization of Polymeric Materials,” Corporate Research 
and Development, Allied Corporation, Academic Press, New York, 1981, pp. 92-563.
10. Mallick, P.K., “Fiber Reinforced Composites: Materials, Manufacturing, and 
Design,” Department of Mechanical Engineering, University of Michigan-Dearbom, 
Michigan, Marcel Dekker Inc., New York, 1988.
11. Hong, X.C., Wing., Y.M., “The Effects of Particle Bulk Modulus on Toughening 
Mechanisms in Rubber-Modified Polymers,” Polymer Engineering and Science, 
October 1998, Vol. 38 HO, pp. 1763-1769.
12. “Tutorial on Polymer Composite Molding,” Developed by The Intelligent Systems 
Lab under the Technology Reinvestment Program,
http://islnotes.cps.msu.edu/trp/index.html, Michigan State University, 1999.
84
13. “Fabricating Tips: Derakane Epoxy Vinyl Ester Resins” Dow Plastics, a business 
group o f The Dow Chemical Company, Form No. 125-00082-196 SMG, Revised 
Edition October 1994, pp. 16-25.
14. Swanson, S.R. “Introduction to Design and Analysis with Advance Composite 
Materials,” Department o f Mechanical Engineering, University o f Utah, Salt Lake, 
Prentice Hall, Ed., 1997, pp. 29-101.
15. Agarwal, B.D., Broutman, L. J.,“Analysis and Performance of Fiber Composites,” 
SecondEdition, Wiley Interscience, 1990, pp. 55-113.
16. Hanks, R.W., “Materials Engineering Science: An Introduction,” Brigham Young 
University, Harcourt, Brace & World, Inc. 1970, pp. 3-14.
17. Strong, BA., “Plastics: Materials and Processing,” Brigham Young University, 
Prentice Hall Ed., 1996, pp.211-235.
18. Blankenship, L.T., White, M.N., Puckett, P.M., “Vinyl Ester Resins: For 
Composites,” Dow Chemical USA, Freeport, Texas, pp. 1-36.
19. Huang, D.D. “Applying fracture Mechanics to material selection,” Plastics 
Engineering, 1996 Society o f Plastics Engineers Inc., June 1996, Vol. 52, No. 6, pp. 
37-40.
20. “Fracture toughness” Guidelines for Characterization o f Structural Materials, 
Military Hand Book 17-1, Section 6.7.7.
21. Davies, P., Benzeggagh, M.L., “Chapter 3, Interlaminar Mode-I Fracture testing,” 
Application o f Fracture Mechanics to Composite Materials, K. Friedrich, Ed., 1989,
pp.81-112.
22. Aliff, N., Carlsson, LA , Gillespie, J.W.,“Mode I, Mode II, and Mixed Mode 
Interlaminar Fracture of Woven Fabric Cafbon/Epoxy, Composite Materials. 
Testing and Design, Thirteen Volume, ASTM STP 1242, S.J. Hooper, Ed., American 
Society for Testing and Materials, 1997, pp. 82-106.
23 . “Standard test Method for Mode I Interlaminar Fracture, toughness of Unidirectional 
fiber-Reinforced Polymer Matrix composites, D5528 -  94a”, 1997 Annual Book o f 
ASTMStandards, Vol. 15.03,1997, pp. 271-279.
24. Haugen, D.J. “Fracture of Skin-Stiffener Intersections in Composite Wind Turbine 
Blade Structures,” Master’s Thesis in Mechanical Engineering, Montana State 
University-Bozeman, August 1998.
85
25. Hunston D.L., “Characterization of Interlaminar Crack Growth in Composites with 
the Double Cantilever Beam Specimen,” National Bureau o f Standard, Polymers 
Division, Washington, D.C., 1985, pp. 2-28.
26. Bradley, W.L., “Chapter 5, Relationship of Matrix Toughness to Interlaminar 
Fracture Toughness,” Application o f Fracture Mechanics to Composite Materials, K. 
Friedrich, Ed., 1989. pp. 159-187.
27. Russell, A.J., Street, K.N., “Factors affecting the Interlaminar Fracture Energy of 
Graphite/Epoxy Laminates,” Progress in Science and Engineering o f Composites, ed. 
Hayashi, T, Kawata, K., and Umekawa, ICCMIV, Tokyo, 1982, pp. 27.
28. Mandell, J.F., Tsai, J.Y., “Effects of Porosity on Delaminatipn of Resin Matrix 
Composites,” Department o f Materials Science and Engineering, Massachusetts 
Institute o f Technology, Massachusetts 02139, April, 1990, pp. 8-10.
29. Scott, M.E., “Effects of Ply Drops on the Fatigue Resistance of Composite Materials 
and Structures,” Master’s Thesis in Chemical Engineering, Montana State University- 
Bozeman, August 1997,
30. “Standard test Method for Deflection Temperature of Plastics Under Flexural Load, D 
648 -  82”, ASTMStandards and Literature Referencesfor Composites Materials,
First Edition 1987, pp. 272-278.
31. Ullett, J.S., Chartoff, R.P. “Toughening of Unsaturated Polyester and Vinyl Ester 
Resins With Liquid Rubbers,” The Center for Basic and Applied Polymer Research, 
University o f Dayton. Dayton, Ohio. Polymer Engineering Science, July 1995, VoL 
35, No. 13, pp. 1086-1096.
32. Babbington, D., Barron, J., Enos, J., Ramsey, R., Preuss, W., “Evolution of RTM , 
with Vinyl Ester Resins,” How to ApplyAdvanced Composites Technology, Fourth 
Annual Conference on Advanced Composites, Dearborn, Michigan, ASM 
International, September 1988, pp. 269-280.
33. Flinn, RA., Trojan, P.K., “Engineering Materials and their Applications,” Third
edition, HughtonMifflin, 1986, pp.61-103. ,
34. Krock, R.H., Broutman, JLJ., “Principles of Composites and Composite 
Reinforcement,” Addison-Wesley Series in Metalurgy and Materials, Addison 
Wesley, 1967, pp. 365G71.
35. Samborsky, D., Master Thesis in Civil Engineering at Montana State University- 
Bozeman, to be published in December 1999.
APPENDIX
Individual Test Results
87
Tensile test results for neat resin.
■ Yield Tensile Maximum
CoRezyn UTS strength
63-AX-051 (MPa) ‘ (MPa) E (GPa) % strain
poly-1 59.63 47.36 3:01 2.4
poly-2 48.26 41.73 . 3.25 1.66
poly-3 54.31 46.48 3.29 1.93
Average 54.07 45.19 3.18 2.00
Std dev 4.64 2.47 0.12
Swancorp 980 (batch a)
12.88M031 25.23 19.96 1.60
M032 25.86 21.13 1.64 26.32
M033 25.85 20.6 1.65 49.33
Average 25.65 20.56 1.63 29.51
Std dev 0.29 0.48 0.02
Swancorp 980 (batch b)
0.716980-1 22.04 3.10
980-2 19.13 2.99 0.66
980-3 24.79 3.06 0.84
Average 21.99 3.05 0.74 -
Std dev 2.31 0.04
Swancorp 901
3.27 1.52901-1 46.91
901-2 35.15 3.40 1.08
901-3 46.32 ■ , 3.43 1.46
Average 42.79 3.37 1.35
Std dev 5.41 0.07
Swancorp 901 & 980 (batch b)
40.89 2 68 4.52100-1 63.89
100-2 65.44 38.73 2.81 4.65
100-3 65.08 44.39 2.80 4.16
Average 64.80 41.34 2.76 4.44
Std dev 0.66 2.33 0.06
thickness
(mm)
2.87
2.84 
2.83
2.85
2.71
2.63
2.67
2.67
3.09
3.14
3.12
3.11
3.18
3.18 
3.20 '
3.19
3.37
3.30
3.31 
3.33
88
Yield
UTS strength Tensile Maximum thickness
Derakane (MPa) (MPa) E (GPa) % strain (mm)
411C-50
41IC-I 57.2 47.13 3.26 2.02 3.23
411C-2 58.79 53.17 3.16 2.14 3.21
411C-3 57.06 50.88 3.21 2.02 3.23
Average 57.68 50.39 3.21 2.06 3.22
Std dev 0.78 2.49 0.04
Derakane
8084
8084-1 75.11 58.35 3.04 3.36 3.32
8084-2 73.81 54.53 3.33 2.95 3.35
8084-3 68.79 52.61 3.38 2.6 3.40
Average 72.57 55.16 3.25 2.97 3.36
Std dev 2.73 2.39 0.15
System 41
sys3-l 51.11 51.11 3.59 1.54 2.77
sys3-2 53.1 ' 53.1 3.63 1.58 2.77
sys3-3 53.62 53.62 3.49 1.67 2.79
Average 52.61 52.61 3.57 1.60 2.78
Std dev 1.08 1.08 0.06
SC-12
scl2-l 41.12 3.48 1.26 3.38
sc 12-2 48.46 3.43 1.55 3.33
sc 12-3 43.44 3.52 1.32 3.35
Average 44.34 3.48 1.38 3.35
Std dev 3.06 0.04
SC-14
scl4-l 72.1 50.06 2.83 3.68 3.36
sc 14-2 66.27 46.81 2.76 3.15 3.37
sc 14-3 66.57 48.62 2.82 3.09 3.36
Average 68.31 48.50 2.80 3.31 3.36
Std dev 2.68 1.33 0.03
Te
ns
ile
 s
tre
ss
 (M
Pa
) 
Te
ns
ile
 s
tre
ss
 (M
Pa
)
89
Stress-strain diagrams for tensile tests on neat resin (3 specimens).
Tension test on neat resin 
CoRezyn 63-Ax-051
Strain (%)
Tensile test on neat resin 
Swancorp 980 batch (a)
(%) Strain
Te
ns
ile
 s
tre
ss
 (M
Pa
) 
St
re
ss
 (M
Pa
)
90
Tensile test on neat resin 
Swancorp 980 batch (b)
Strain (%)
Tensile test on neat resin 
Swancorp 901
Strain (%)
Te
ns
ile
 s
tre
ss
 (M
Pa
) 
Te
ns
ile
 s
tre
ss
 (M
Pa
)
91
Tension test on 50-50% blend 
of Swancorp 901 & Swancorp 980
Strain (%)
Tension test on neat resin 
Derakane 411C-50
Strain (%)
Te
ns
ile
 s
tre
ss
 (M
Pa
) 
Te
ns
ile
 s
tre
ss
 (M
Pa
)
92
Tension test on neat resin 
Derakane 8084
Strain (%)
Tension test on neat resin 
System 41
Strain (%)
Te
ns
ile
 s
tre
ss
 (M
Pa
) 
Te
ns
ile
 s
tre
ss
 (M
Pa
)
93
Tension test on neat resin 
SC-12
Strain (%)
Tension test on neat resin 
SC-14
Strain (%)
94
Results for heat deflection temperature (HDT) tests on neat resin.
CoRezyn
63-AX-051 HDT (0C)
poly-1 53.60
poly-2 55.34
poly-3 55.08
Average 54.67
Std dev 0.94
Swancorp 980 batch (b).
980-1 57.42
980-2 .60.13
980-3 60.63
Average 59.39
Std dev 1.73
Derakane 411C-50
41lc-1 73.5
411c-2 80.157
411c-3 79.59
Average 77.75
Std dev 3.69
Derakane
8084
8084-1 72.60
8084-2 74.70
8084-3 75.20
Average 74.17 '
Std dev 1.38
System 41
sys3-l 59.38
sys3-2 52.90
sys3-3 53.28
Average 55.19
Std dev 3.64
thickness (mm) load (gr)
2.85 592
3.11 638
3.38
3.41
3.33
3.37 682
3.36 683
2.78 581
SC-12 HDT (0C)
95
thickness (mm) load (gr)
scl2-l 92.74 3.40 ' ■
sc 12-1 94.75 3.40 ,
sc 12-1 94.95 3.40
Average 94.15 3.40 703
Std dev 1.22
SC-14
scl4-l 80.49 3.37
sc 14-2 82.69 3.40
sc 14-3 84.28 3.42
Average 82.49 3.40 680
Std dev 1.90
96
Results for 90° tension of [0/±45/0]s composites.
CoRezyn UTS Knee stress
63-AX-051 (MPa) (MPa)
1T01 68.19 29.9
1T02 75.24 29.9
1T03 77.80 28.6
Average 73.75 29.47
Std dev 4.06 0:61
Swancorp 980 (batch a)
55.92T01 105.3
2T02 106.6 50.7
2T03 • 110.3 49.7
Average 107.40 52.10
Std dev 2.12 2.72
Poly 15-D65
37:63T01 89.4
3T02 117.9 37.9
3T03 116.1 39.9
Average 107.80 38.47
Std dev 13.03 1.02
System 41
4T01 108.5 60.9
4T02 122:1 60.4
4T03 110.5 60.1
Average 113.70 60.47
Std dev 6.00 0.33
Derakane 411C-50 (39% Vf)
ts411-l 57.61 ' ' 35.4
ts411-2 54.77 36.6
ts411-3 56.59 36.6
Average 56.32 36,20
Std dev 1.17 0.57
Derakane 411C-50 (35% Vf)
t411-l 59.88 45.15
t411-2 58.56 44.44
t411-3 58.88 49.52
Average 59.11 46.37
Std dev 0.56 2.25
Tensile 
E (GPa) 
10.65 
10.52 
10.10 
10.42 
0.23
7.09
6.98
6.65
6.91
0.19
5.47
5.65
5.57
5.56
0.07
11.66
11.75
11.48
11.63
0.11
9.25
9:24
9.45
9.31
0.09
Maximum 
% strain 
2.26 
3.14 
3.51 
2.97 
0.52
3.71
3.85
3.88
3.81
0.07
3.51
5.42
4.68
4.54
0.79
3.02
3.8
3.34
3.39
0.32
4.39
4.92
4.01
4.44
0.37
(% Vf) Fiber 
volume 
37.3 •
37.38
37.56
37.41
36.72
36.04
36.04 
36.27
38.48 
38.62
38.48 
38.53
42.25
42.84
42.31
42.47
39.15 
39.02
39.28
39.15
8.03 4.32 35.32
8.13 3.95 35.59
8.49 3.54 35.59
8.22 3.94 35.50
0.20 0.32
97
Derakane 8084 UTS Knee stress
(39% Vf) (MPa) (MPa)
ts8084-l 63.79 43.60
ts8084-2 67.44 44.90
ts8084-3 64.04 42.00
Average 65.09 43.50
Std dev 1.66 1.19
Tensile , Maximum (%  V f )  Fiber
E (GPa) % strain , volume
9:27 5.07 39.54
9.52 4.04 39.54
8.55 . 4.35 39.54
9.11 4.49 39.54
0.41 0.43
Derakane 8084
(35% Vf) 
t8084-l . 62.74 44.25. 8.61 3.70 35.32
t8084-2 62.87 45.07 8.33 4.39 ' 35.32
18084-3 63.31 43.17 • 8.11 . 4.21 ■ 35.32
Average 62.97 44.16 8.35 4.10 35.32
Std dev 0.24 0.78 0.21 0.29
SC-14
tscl4-l 108.65 61.5 9.37 3.21 . 37.43
tscl4-2 120.75 60.9 9.51 4.73 37.83
tscl4-3 104.44 59.2 9.36 3.45 37,96
Average 111.28 60.53 9.41 3.80 37.74
Std dev 6.91 0.97 0.07 0.67
98
Stress-strain diagrams for 90° tensile test of [0/+45/0]s composites (3 specimens).
100
« 80 
$
6  v  60
— % /n
90° tension of CoRezyn 63-AX-051 
[0/+45/0]s 37% Vf
» B. 40
H ZU
0  4
)
% SI
’ 3 4
train
99
140
« 120
90° tension of Poly 15-D65 
[0/+45/0]s 33% Vf
a) 100
« « 80 0) u_
■3; I .  60
a> 40
20  
o - _____ I-------—
ID 0 5 1.5 2 2.5 3 3.5
% Strain
90° tension of System 41 
[0/+45/0]s 42% Vf
140
Ot 120OT2 100 -T1 ■—■ __OT OT S0 -
OT &  60 ^
g 40
H  20 
0
0 0.5 1 1.5 2 2.5 3 3.5
% Strain
4
100
90° Tension of Derakane 411C-50 
[0/+45/0]s 35% Vf
% Strain
90° tension of Derakane 411C-50 
[0/+45/0]s 39 % Vf
70
$
S ^  50<0 re 40 8^gTTjH—
T
en
si
le (M
F
M
 
W
 
O
O
O
O - t
r -
Q O.5 1 1 .5 2 2.5 3 3.5 4 4.5 5 5.5
% Strain
101
90° Tension of Derakane 8084 
[0/+45/0]s 35% Vf
S 30
% Strain
90° tension of Derakane 8084 
[0/+45/0]s 39 % Vf
O ^  40
% Strain
102
140
90° Tension of Epoxy SC-14 
[0/+45/0]s 38% Vf
_____ ^« 120
" ' J--------100
« 2  80
» & 60
S 40
20  
o -
r y i
D 0 5 1 5 2 2
% S
5
train
3 3.5 4 4.5
103
Results for 0° compression test of [0/±45/0]s composites.
CoRezyn Compressive
63-AX-051 strength (MPa)
ICOl 484.69
1C02 541.04
1C03 526.43
Average 517.39
Std dev 29.24
Swancorp 980 (batch a)
2C01 447.05
2C02 397.06
2C03 ' 417.00
Average 420.37
Std dev 25.17
Poly 15-D65
3C01 404.12
3C02 376.94
3C03 355.75
Average 378.93
Std dev 24.25
System 41
4C01 596.63
4C02 516.13
4C03 590.64
Average 567.80
Std dev 44.85
Derakane 411C-50 (39% Vf)
411-1 432.86
411-2 462.80
411-3 458.42
Average 451.36
Std dev 16.17
Derakane 411C-50 (35% Vf)
t411c-l 587.88
t411c-2 548.25
t411c-3 581.05
Average 572.39
Std dev 21.19
Maximum thickness Vf
Load (kg) (mm) (%)
3768.88 2.98 37.38
4563.12 3.26 34.48
4329.06 3.18 35.32
4220.35
408.13
3.14 35.73
3411.45 3.00 . 37.17
3156.53 3.10 36.11
3364.28 3.14 35.72
3310.75 3.08 36.33
135.63
3056.29 2.91 38.09
2960.58 3.01 37.04
2842.19 3.08 36.32
2953.02 3.00 37.15
107.25
4521.84 2.87 38.49
3904.05 2.83 38.95
4441.10 2.88 38.36
4289.00 2.86 38.60
335.81
3265.85 2.90 38.22
3457.72 2.84 38.75
3310.30 2.77 39.54
3344.62 2.84 38.84
100.43
4848.88 3.18 35.32
4526.37 3.20 35.06
4740.02 3.18 35.32
4705.09 3.18 35.23
164.06
104
Derakane Compressive
8084 (39% Vf) strength (MPa)
808-1 470.76
808-2 465.92
808-3 448.12
Average 461.60
Std dev 11.92
Derakane 8084 (35% Vf)
t8084-l 510.16
t8084-2 585.43
t8084-3 528.76
Average 541.45
Std dev 39.21
SC-14
sc 14-1 523.89
sc 14-2 527.16
sc 14-3 543.86
Average 531.64
Std dev 10.71
Maximum Thickness Vf
Load (kg) (mm) (%)
3517.14 2.87 38.49
3436.40 2.82 39.02
3339.78 2.86 38.62
3431.11
88.80
2.85 38.71
4228.82 3.20 35.06
4862.48 3.20 35.06
4342.67 3.23 34.79
4477.99
337.81
3.21 34.97
4089.11 3.02 36.91
4080.04 . 3.00 37.17
4209.32 3.00 37.17
4126.16 3.01 37.08
72.16
105
T-Pull off test results.
CoRezyn Initial Displacement Maximum Displacement
63-AX-051 damage at initial Load at maximum
Specimen load (N/cm) damage (cm) (N/cm) load(cm)
2601 82 0.23 134 0.68
2602 93 0.26 141 0.74
1505 86 0.22 129 0.63
Average 87 0.24 135 0.68
Std dev 5.57 0.02 6.03 0.06
PET-P460
2305 120 0.3 164 0.84
Swancorp 980 (batch a) 
2501 . 114 0.58 172 1.59
2502 108 0.51 176 1.24
2503 125 0.62 183 1.25
2504 123 0.6 188 1.56
Average 119 0.58 182 1.35
Std dev 9.29 0.06 6.03 0.18
Derakane 8084 
2801 138 0.47 192 0.89
2802 150 0.51 195 0.91
Average, 144 0.49 194 0.90
Std dev
System 41 
2701 161 0.37 210 0.67
2702 175 0.39 207 0.67
Average 168 0.38 209 0.67
Std dev
SC-14
2901 140 0.6 198 1.91
2902 123 0.59 186 1.91
Average 132 0.60 192 1.91
Std dev
Poly 15-D65 
2408 141 0.46 262 1.16
Flange + Skin 
tickhess (mm) 
5.62 
5.74 
6.37 
5.91
6.69
5.91
5.88
5.9
5.93
5.90
5.25
5.15
5.20
6.33
5.99
6.16
5.37
5.29
5.33
6.54
L
oa
d 
(N
/c
m
) 
Lo
ad
 (N
/c
m
)
106
Load-displacement diagrams for T Pulloff tests.
T Pulloff test of CoRezyn 63-AX-051 
3 specimens
T - Pulloff test of Swancorp 980 (batch a) 
4  specimens
Displacement (cm)
Lo
ad
 (N
/c
m
) 
Lo
ad
 (N
/c
m
)
107
I  Pullofftest of PET P460 
1 specimen
Displacement (cm)
T Pulloff test of Poly 15-D65 
1 specimen
Displacement (cm)
108
T Pulloff test of Derakane 8084 
2 specimens
Displacement (cm)
T Pulloff test of System 41 
2 specimens
100
Displacement (cm)
109
T Pulloff test in SC-14 
2 specimens
200
1:
:g 150
M 100
5  Sn50
o -I
) 0 5 1
Displacer
5
nent (cm)
I 2.5 3
no
Summary of DCB results for [0]e composites.
Polyester
CoRezyn 63-AX-051
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
(J/mA2) (J/mA2)
1011 162 179 345 5
1012 . 152 ' 152 I
1013 139 139 ' I
1014 157 138 148 2
Average 153 159 196 Total
Tests
Std Dev 10 29 99 7
Polyester PET P460
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
(J/mA2) (J/mA2)
1021 111 220 229 3
1022 232 297 264 2
1023 116 133 124 2
1025 139 239 189 2
1026 121 205 196 3
Average 144 219 201 . Total
Tests
Std Dev 50 59 52 12
Polyester Arotran Q6038
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
(J/mA2) (J/mA2)
1061 153 309 235 3
CoRezyn 63-AX-051 using bonded fabric with polyester veil
(Veil-Veil)
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
1111
(J/mA2)
202
(J/mA2) 
258 ' 326 5
1112 229 294 287 . ' ■ 3 . '
Average 216 276 307 „ Total
Std Dev
■ Tests 
8
I l l
CoRezyn 63-AX-051 using bonded fabric with glass Veil
(Veil-Veil)
Overall Gic (J/mA2)Specimen Gic (a) initial Gic (b)
(J/mA2) (J/mA2)
1121 209 360 357 .
1122 167 187 226
Average 188 274 292
Std Dev
Tests Performed
4
3
Total
Tests
I
CoRezyn 63-AX-051 using bonded fabric with polyester veil (Glass-
Glass)
Specimen Gic (a) initial Gic (b)
(J/mA2) (J/mA2)
1131 130 116
1132 98 165
Average 114 141
Std Dev
Overall Gic (J/mA2) Tests Performed
143 3
168 3
156 Total
Tests
6
Vinyl ester Swancorp 980 (batch a)
Specimen Gic (&) initial Gic (b) Overall Gic (J/m 2) 
(J/mA2) (J/mA2)
1031 1308 1758 1869
1032 1635
1033 1754
1034 1066
Average 1441
Std Dev 313
Vinyl ester Derakane 8084
Specimen Gic (a) initial 
(J/mA2)
1091 348
1092 335
1093 347
Average 344
Std Dev 7'
1666 1908
2030 2060
1906 1855
1840 1923
161 94
Gic (b) Overall Gic (J/mA2)
(J/mA2) ■
442 472
671 . ■ 496
673 606
595 524
133 71
Tests Performed
4
5 
3 
3
Total
Tests
15
Tests Performed
5
3
3
Total
Tests
11
112
Vinyl ester Derakane 
411C-50
Specimen Gic (a) initial Gic (b)
(J/mA2) (J/mA2)
1101 231 493
1102 238 298
Average 234 396
Std Dev
Vinyl ester Swancorp 901
Specimen Gic (a) initial Gic (b)
(J/mA2) (J/mA2)
901-1 193
901-2 230
901-3 200
Average 208
Std Dev 20
Vinyl ester Swancorp 901 & 980
(batch b) 
Specimen Gic (a) initial Gic (b)
(J/mA2) (J/mA2)
100-1 552
100-2, 560
100-3 595
Average 569
Std Dev 23
Vinyl ester Swancorp 980 (batch b)
Specimen Gic (a) initial Gic (b)
(J/mA2) . (J/mA2)
980-1 670 846
980-2 641
980-3 1070
Average 852
Std Dev 215
Overall Gic (J/mA2) Tests Performed
539 5
343 3
441 Total
Tests 
8
Overall Gic (J/mA2) Tests Performed
306 3
299 3
262 3
289 Total
Tests
24 9
Overall Gtc (J/mA2). Tests Performed
638 3
587 3
679 3
635 Total .
Tests
46 9
Overall Gic (J/mA2) Tests Performed
803 4
708 • 3
915 3
809 Total
Tests
104 1.0
113
Epoxy - System 41 
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
1041
Il (J/mA2)
263 294 5
1042 220 • 240 229 3
1043 196 189 215 3
Average 219 231 246 Total
Std Dev 22 38 42
Tests
11
Epoxy SC-14 
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
1071
(J/mA2)
703
(J/mA2)
589 653 5
1072 591 511 584 4
1073 621 814 692 3
Average 638 638 643 Total
Std Dev 58 157 55
Tests
12
Epoxy SC-12 
Specimen Gic (a) initial Gic (b) Overall Gic (J/mA2) Tests Performed
1081
(J/mA2)
379
(J/mA2)
445 511 5 •
1082 315 409 365 3
Average 347 427 438 Total
Std Dev
Tests
8
Polyurethane Poly 15-D65
Specimen Gic (a) initial 
(J/mA2)
Gic (b) 
(J/mA2)
Overall Gic (J/mA2) Tests Performed
1051 2411 2752 2512 4
1052 2914 2914 I
Average 2663 2752 2713 Total
Tests
5
114
Individual DCB test results. 
CoRezyn 63-AX-051
Specimen b= 2.5146 cm initial a (cm) Overall
1011 disp (mm) load (kg) 4.72 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 5.66 2.31 4.89 161.92 344.80 176.23
b) 6.56 2.28 5.28 178.77
c) 10.78 3.02 5.65 360.74
d) 13.33 3.26 6.17 449.95
e) 17.70 3.41 572.63
b= 2.48 cm initial a (cm) Overall
1012 disp (mm) load (kg) 4.75 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 5.61 2.17 4.84 . 151.63 151.63
b= 2.48 cm initial a (cm) Overall --
1013 disp (cm) load (kg) 4.73 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 5.04 2.21 4.88 139.28 139.28
b= 2.53 cm initial a (cm) Overall
1014 disp (mm) load (kg) 4.75 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 5.64 2.28 ■ 4.87 157.22 147.73 13.43
b) 5.69 2.03 138.23
Polyester PET P460
■
b= 2.54 cm initial a (cm) Overall
1021 disp (mm) load (kg) 4.44 GIC GIC (J/mA2) Stdev
(J/mA2) ,
a) Initial 4.11 2.07 4.52 110,78 228.97 123.12
b) 6.20 2.77 4.80 219.63
c) 8.55 3.46 5.13 356.50
b= 2.56 cm initial a (cm) Overall
1022 disp (mm) load (kg) ' 4.53 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 6.37 2.87 4.96 231.82 264.48 46.18
b) 8.40 3.05 297.14
115
b= 2.52 cm initial a (cm) Overall
1023 disp (mm) load (kg) 4.47 GIC GIC (J/mA2) • Stdev
(J/mA2)
a) Initial 4.34 2.04 4.67 115.73 124.29 12.10
b) 4.82 2.20 4.80 132.85
b= 2.53 cm initial a (cm) Overall
1025 disp (mm) load (kg) 0.91 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 0.25 8.61 1.26 138.64 189.06 71.29
b) 0.65 7.95 • 1.43 239.47
b= 2.52 cm initial a (cm) Overall
1026 disp (mm) load (kg) 0.48 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 0.10 10.24 1.29 120.83 195.62 70.45
b) 0.38 11.95 2.21 205.29
O 1.06 9.30 2:63 260.74
Polyester Arotran Q6038
b= 2.37 cm initial a (cm) Overall
1061 disp (mm) load (kg) 1.05 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 0.30 8.80 1.58 153.15 234.90 78.00
b) 0.87 9.04 2.11 308.51
c) 1.18 6.98 2,44 243.04
CoRezyn 63-AX-051 using bonded fabric with polyester veil
(Veil-Veil)
Overallb= 2.54 cm initial a (cm)
Stdev1111 disp (mm) load (kg) . 2.43 GIC GIC (J/mA2)
(J/mA2)
a) Initial 1.76 4.80 2.89 201.68 326.47 115.39
b) 2.55 5.06 2.97 258.28
c) 3.02 5.33 \  3.15 314.90
d) 3.44 5.55 3.23 351.33
e) 4.50 6.26 3.39 . 506.15
b= 2.54 cm initial a (cm) Overall
1112 disp (mm) load (kg) 2.49 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 1.97 5.02 2.81 229.49 287.91 . 55.62
b) 2.85 5.00 3.17 294.01
c) 3.63 5.13 3.64 340.23
1.16
CoRezyn 63-AX-051 using bonded fabric with glass Veil
(Veil-Veil)
b= 2.54 cm initial a (cm) Overall
1121 disp (mm) load (kg) 2.43 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 1.87 4.70 2.66 209.38 356.95 105.44
b) 2.83 5.82 2.87 360.12
c) 3.42 5.85 , 3.14 405:28
d) 4.30 5.72 3.41 453.03
b= 2.52 cm initial a (cm) Overall
1122 disp (mm) load (kg) 2.29 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 1.36 4.81  ^ 2.68 166.90 226.32 86.21
b) 1.78 4.81 2.97 186.86
c) 2.94 5.64 3.45 325.20
CoRezyn 63-AX-051 using bonded fabric with polyester veil Overall
(Glass-Glass)
b= 2.54 cm initial a (cm) GIC (J/mA2) Stdev
1131 disp (mm) load (kg) 2.47 GIC 142.82 34.69
(J/mA2)
a) Initial 1.50 3.69 2.85 129.94 '
b) 1.83 3.13 3.26 116.41
c) 2.93 3.50 3.72 182.11
b= 2.55 cm initial a (cm) Overall
1132 disp (mm) load (kg) 2.48 GIC GIC (J/mA2) Stdev
(J/mA2).
a) Initial 1.23 3.44 2.73 97.97 168.12 71.71
b) 1.96 4.00 3.00 165.09
0 2.78 4.53 3.31 241.30
Vinyl ester Swancorp 980 (batch a)
b= 2.51 cm initial a (cm) Overall
1031 disp (mm) load (kg) 1.69 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 2.67 14,15 1.98 1308.20 1868.50 459.61
b) 3.45 17.28 2.26 1757.57
c) 4.61 16.79 2.66 2001.36
d) 6.59 16.63 3.17 2406.86 1
117
1032
b= 2.53 cm 
disp (mm) load (kg)
a) Initial 3.03 16.13
b) 3,13 17.32
c) 4.32 16.47
d) 4.97 .16.0.1
e) 7.06 15.83
1033
b= 2.53 cm 
disp (mm) load (kg)
a) Initial 2.85 18.72
b) 3.62 19.48
c) 4.52 19.42
1034
b= 2.52 cm 
disp (mm) load (kg)
a) Initial 2.21 14.48
b) 3.51 17.59
O 4.60 19.90
Vinyl ester Derakane 8084
b= 2.55 cm
1091 disp (mm) load (kg)
a) Initial 2.50 5.92
b) 2.97 6.50
c) 4.44 7.29
d) 4.22 4,89
e) 5.48 . 5.53
b= 2.54 cm
1092 disp (mm) load (kg)
a) Initial 2.60 5.56
b) 4.97 6.73
c) 5.11 5.16
initial a (cm) Overall
1.74 GIC (J/mA2) Stdev
1.89 1634.51 1907.56 289.89
2.14 1666.00
2.38 1936.70
2.76 1944.67 .
2.93 2355.90
initial a (cm) Overall
1.77 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.02 1753.84 2059.81 321.96
2.13 2029.91
2.61 2395.68
initial a (cm) Overall
1.75 GIC
(J/mA2)
GIC (J/mA2) Stdev
1.89 1066.45 1855.03 764.57
2.06 1905.55
2.47 2593.09
initial a (cm) 
2.46 GIC
Overall 
GIC (J/mA2) Std'ev
' 2.52
(J/mA2)
348.39 ,471.56 127.52
2.80 442.14
3.13 668.69
3.38 381.63
3.60 516.94
initial a (cm) 
2.50 GIC
Overall 
GIC (J/mA2) Stdev
2.89
(J/mA2)
335.36 495.96 168.48
3.18 671.33
3.94 481.19
118
1093
b= 2.52 cm 
disp (mm) load (kg)
a) Initial 2.52 5.71 .
b) 3.91 7.49
c) 5.42 7.37
Vinyl ester Derakane 411C-50
1101
b= 2.53 cm 
disp (mm) load (kg)
a) Initial 2.13 4.65
b) 3.56 6.28
c) 5.07 6.08
d) 5.42 5.55
e) 7.49 6.45
1102
b= 2.53 cm 
disp (mm) load (kg)
a) Initial 2.31 4.51
b) 2.88 4.74
c) 4.78 5.51
Vinyl ester Swancorp 901
901-1
b= 2.55 cm 
disp (mm) , load (kg)
a) Initial
b) 1.59 5.08
c) 3.25 6.30
d) 4.37 4.58
901-2
b= 2.55 cm 
disp (mm) load (kg)
a) Initial
b) 1.78 5.13
c) 2.30 5.31
d) 2.97 . 5.72
initial a (cm) Overall
2.42 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.55 346.96 605.54 232.41
2.93 672.64
3.26 797.01
initial a (cm) ' Overall
2.50 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.63 230.61 538.78 212.59
2.98 493.07
3.18 599.53
3.42 549.23
. 3.80 821.46
initial a (cm) Overall
2.54 P GIC (J/mA2) Stdev
2.66 238.00 343.27 133.52
3.10 298.37
3.48 493.46
initial a (cm)
GIC
(J/mA2)
Overall 
GIC (J/mA2) Stdev
2.41 306.48 110.61
2.85 193.30
3.70 414.32
4.88 311.81
initial a (cm)
GIC
(J/mA2)
Overall 
GIC (J/mA2) Stdev
2.30 299.41 . 73.30
2.41 229.80
2.61 292.53
2.85 375.91
119
901-3
b= 2.55 cm 
disp (mm) load (kg)
a) Initial
b) 2.06 4.04
c) 2.87 4.99
d) 3.30 4.17
Vinyl ester Swancorp 901& 980
(batch b) 
100-1
b= 2.55 cm 
disp (mm) load (kg)
a) Initial
b) 3.81 6.49
c) 5.64 6:49
d) 8.28 5.26
100-2
b= 2.54 cm 
disp (mm) load (kg)
a) Initial
b) 4.14 $.35
c) 5.74 5.72
d) . 8.23 4.90
100-3
b= 2.55 cm 
disp (mm) load (kg)
a) Initial
b) 3.76 7.08
c) 5.33 6.94
d) 6.91 6.12
initial a (cm)
P
Overall 
GIC (J/mA2) Stdev
2.40 262.46 56.85
2.66 199.92
2.88 310.98 -
3.11 276.49
initial a (cm) Overall
GIC GiC (J/mA2) Stdev
(J/mA2)
2.58 . 637.64 75.36
3.04 552.06
3.77 ' 694.08 .
4.41 666.78
initial a (cm)
GIC
(J/mA2)
Overall 
GIC (J/mA2) Stdev
2.73 587.47 24.37
3.19 559.74
3.86 597.18
4.87 605.49
initial a (cm)
GIC
(J/mA2)
Overall 
GIC (J/mA2) Stdev
2.58 678.75 73.53
2.91 594.97
3,44 732.61
4.23 708.65
120
Vinyl ester Swancorp 980 (batch b)
b= 2.55 cm initial a (cm) Overall
980-1 disp (mm) load (kg) 2.06 GIC GIC (J/mA2) Stdey
(J/mA2) '■ ' .
a) Initial 2:74 8.75 2.45 670.36 803.26 113,38
b) 4.11 8.75 2.94 845.75
c) 5.54 7.03 3.77 . 761.82
d) 9.30 6.58 5.04 935.10
b= 2.55 cm initial a (cm) Overall
980-2 disp (mm) load (kg) GIC GIC (J/mA2) Stdey
(J/mA2)
a) Initial 2.26 707,60 60.17
b) 3.48 7.21 2.84 641.23
c) 5.49 6.49 3.41 723.01
d) 7.67 5.85 4.42 758.57
b= 2.59 cm initial a (cm) Overall
980-3 disp (mm) load (kg) GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial . 2.26 914.94 144,08
b) . 4.19 10.16 2.80 1070.41
c) 5.13 7,53 3.35 785.90
d) 7.65 6.85 3.96 888.52
Epoxy - System 41 • ■
b= 2.49 cm initial a (cm) Overall
1041 disp (mm) load (kg) 1.34 GIC GIC (J/mA2) Stdev
(J/mA2)
a) Initial 0.69 7.95 1.64 . 240.44 293.55 , 54.63
b) 0.97 7.50 2.05 263.05 -
c) 1.43 6,81 2.57 .279.57
d) 2.18 6.03 3.00 302.14
e) 3.23 6.01 3.85 382.53
b= 2.58 cm initial a (cm) - Overall
1042 disp (mm) load (kg) 1.39 GIC GIC (J/mA2) Stdev
•• (J/mA2)
a) Initial 0.60 8.88 1.63 219.97 229.19 10.14.
b) 0.83 8.30 1.98 240.05
c) 1.13 . 6.97 2.19 227.57
121
b= 2.8 cm
1043 disp (mm) load (kg)
a) Initial 0.74 7.06
b) 0.80 7.63
c) 1.26 8.03
Epoxy
SC-14 b= 2.47 cm
1071 disp (mm) load (kg)
a) Initial 1,68 11.21
b) 2.48 8.55
c) ■ 3.57 8.52
d) 5.15 6.21
e) 6.85 5.61
1072
b= 2.47 cm 
disp (mm) load (kg)
a) Initial 1.86 9.87
b) 2.32 7.99
c) 3.20 8.90
d) 3.62 6.46
1073
b= 2.5 cm 
disp (mm) load (kg)
a) Initial 2.60 8.99
b) 3.93 8.62
c) 5:04 6.57
Epoxy
SC-12 b= 2.53 cm
1081 disp (mm) load (kg)
a) Initial . 2:43 6.26
b) 3.71 5.79
c) 5.57 5.87
d) 7.07 4.56
e) 9.58 4.86 -
initial a (cm) Overall
1.40 P GIC (J/mA2) Stdev
1.71 196.01 215.11 39.52
2.04 188.77
2.43 260.55
initial a (cm) Overall
1.59 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.14 . 703.00 653.34 65.85
2.44 589.26
3.13 . 741.91
3.66 606.79
4.10 625.73
initial a (cm) Overall
1.85 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.16 591.19 583.87 114.32
2.28 - 510.56
2.83 742.57
3.65 491.16
initial a (cm) 
2.22 GIC
Overall 
GIC (J/mA2) Stdev
2.44
(J/mA2)
620.51 692.27 106.05
3.03
3.40
814.08
642.21
initial a (cm) Overall
2.34 GIC
(J/mA2)
GIC (J/mA2) Stdev
2.81 379.05 510.95 109.50
3.22 ' 444.79
3.83 591.84
4.18 489.64
5.41 649.46
122
1082
b= 2.53 cm 
disp (mm)
a) Initial 2.23
b) 3.39
c) 4.27
Polyurethane Poly 15-D65
1051
b= 2.57 
disp (mm)
a) Initial 4.20 .
b) 6.40
c) 7.57
d) 9.55
1052
b= 2.56 
disp (mm)
a) Initial 5.00
initial a (cm)
load (kg) 2.34
5.69 ■ 2.73
5.66 . 3.20
4.77 3.49
initial a (cm)
load (kg) 1.93
19.40 2.36
17.71 2.67
14.81 3.13
14.23 4.1:4
initial a (cm)
load (kg) 2.06
20.90
Overall
C; rs GIC (J/mA2) Stdev
315.16 365.09 47.31
409.24
370.87
OverallP GIC (J/mA2) Stdev
2410.92 2512.33 163.07
2751.64
2406.57
2480.19
Overall
GIC . GIC (J/mA2) Stdev
(J/mA2)
2914.28 2914.28
123
Results for Enf tests of [0]g composites. 
CoRezyn crack length 
63-Ax-OSI from support
Specimen center a (cm) load (kg) h (mm) Vf EL* (GPa) GIIC
(J/mA2)
1012 3.77 38.92 1.69 0.40 33.15 1169
1013 2.33 51.71 1.72 0.39 32.56 724
1014 1.86 74.84 1.68 0.40 33.36 1037
Average 2.66 55.16 1.69 0.40 33.03 977
Std dev 0.99 18.21 0.02 0.01 0.42 229
Polyester PET-P460
1021 2.18 83.46 1.70 0.40 32.92 1729
1022 3.55 54.88 1.73 0.39 32.42 1848
1023 3.86 47.17 1.73 0.39 32.31 1679
1025 3.90 56.25 1.89 0.35 29.41 2072
Average 3.77 52.77 1.78 0.37 31.38 1866
Std dev 0.19 4.89 0.09 0.02 1.70 197
Polyester Arotran Q6038
1061 1.02 85.27 1.97 0.33 28.04 305
Vinylester Swancorp 980 (batch a)
1031 1.89 124.28 1.91 0.35 29.21 2358
1032 2.67 102.51 1.95 0.33 28.40 3017
1033 3.13 100.24 1.96 0.33 28.29 3972
Average 2.57 109.01 1.94 0.34 28.63 3116
Std dev 0.63 13.27 0.03 0.01 0.50 812
Vinylester Derakane 411C-50
1101 2.49
1102 3.70
Average 3.09
Std dev
Vinylester Derakane 8084
1091 1.86
1092 2.65
1093 v 3.09
Average 2.53
Std dev 0.62
81.65 1.56 0.43 35.45 2620
54.43 1.57 0.43 35.22 2495
68.04 1.57 0.43 35.34 2557
95.25 1.57 0.43 35.17 1992
82.10 1.54 0.43 35.86 3054
69.40 1.57 0.43 35.29 2867
82.25 1.56 0.43 35.44 2638
12.93 0.02 0.00 0.37 567
124
Epoxy crack length
System 41 from support
Specimen center a (cm) load (kg) h (mm) ' Vf EL*(GPa) GIIC
(J/mA2)
1041 1.74 141.07 1.89 0.35 29.39 2593**
1043 2.95 102.51 1.89 0.35 29.53 3776
Average 2.35 121.79 1.89 0.35 29.46 3776
Std dev
Epoxy SC-14
1071 1.89 119.75 1.72 0.39 32.64 2769
1072 2.91 83.01 1.72 0.39 32.63 3110
1073 3.19 84.82 1.71 0.39 32.65 3791
Average 2.66 95.86 1.72 0.39 32.64 3223
Std dev 0.68 20.71 0.00 0.00 0.01 520
Epoxy SC-12
1081 2.41 80.29 1.57 0.43 35.27 2350
1082 2.98 70.31 1.57 0.43 35.17 2710
Average 2.69 75.30 1.57 0.43 35.22 2530
Std dev
Polyurethane Poly 15-D65
- . ■
1051 2.33 121.56 1.99 0.32 27.60 3145**
** Specimens failed in compression, no crack propagation occurred.
I "
125
Results for 90° tension test of [0/+45/0]s wet composites after 330 hrs.
CoRezyn UTS Knee stress Tensile Maximum Fiber
63-AX-051 (MPa) (MPa) E (GPa) % strain Volume (Vf)
1T04 77.17 27.02 • 8:94 2.95 36
1T05 71.92 28.44 8.68 2.78 36
1T06 75.83 28.3 9.02 2.79 36
Average 74.97 27.92 8.88 2.84 36.00
Std dev 2.23 0.64 0.15 0.08
Swancorp 980 (batch a) 
2T04 99.67 50.13 6.33 3.94 36
2T05 99.71 49.27 6.59 3.97 35
2T06 105.06 46.96 6.88 4.31 36
Average 101.48 48.79 6.60 4.07 35.67
Std dev 2.53 1.34 0.22 0.17
Poly 15-D65
3T04 81.31 28.68 3.1 3.3 37
3T05 82.37 22.57 2.73 4.06 37
3T06 76.11 28.5 2.91 3.98 37
Average 79.93 26.58 2.91 3.78 37.00
Std dev 2.74 2.84 0.15 0.34
System 41 
4T04 101.62 57.92 9.69 2.93
4T05 . 101.93 56.89 ■ 10.74 2.45 40
4T06 96 57.9 10.06 3.28 38
Average 99.85 57.57 10.16 2.89 40.00
Std dev 2.73 0.48 0.43 0.34
126
Results for 0° compression test of [0/+45/0]s wet composites after 330 hrs
90° tension of CoRezyn 63-AX-051 
[0/+45/0]s (wet) 37% Vf
O U
T
en
si
le
 s
tr
es
s
_ 
M
 
Jl
uIP
aL
 m
 
-
o
o
o
o
o
o
o
c --
) 0 5 1.5 2 2.5 3 3.5
(%) Strain
90° tension of Swancorp 980 batch (a) 
[0/+45/0]s (wet) 36% Vf
% Strain
127
90° tension of Poly 15-D65 
[0/+45/0]s (wet) 33% Vf
- i nn ..... . _ _ _ ... . . _
M  on
OT tiU
S •—. en .
I
</) CTJ OU
<2 B ^  _
COTi— onZU
nU i
C 0 5 1 5 2
% SI
2
train
5 : 3 5 /
90° tension of System 41 
[0/+45/0]s (wet) 42% Vf
I ^ .U
v> 100
<f)
QfX-b ^  oU
OT CO
to “  OU 
C  -  4 n _____________ _____________
O
H  2 0 Z/
I
U  I--------------------------
0 I >
I (%)
) /
128
Results for 0° compression test of [0/+45/0]s composites after water absorption.
CoRezyn Compressive Maximum thickness Vf
63-AX-051 strength (MPa) Load (kg) (mm) (%)
1C04 433.77 3552.52 3.13 35.72
1C05 470.15 3753.46 3.06 36.44
1C06 401.64 3277.64 3.12 35.85 '
Average 435.19 3527.87 3.10 36.00
Std dev 34.28 238.87
Swancorp 980 (batch a)
2C04 411.90 3243.17 3.09 36.11
2C05 403.95 3295.30 3.19 35.13
2C06 432.77 3376.10 3.07 36.37
Average 416.21 3304.86 3.12 35.87
Std dev 14.88 66.98
Poly 15-D65
3C04 245.45 1888.30 2.97 37.43
3C05 291.35 2261.60 2.97 37.43
3C06 259.68 2046.14 3.02 36.90
Average 265.49 2065.35 2.99 37.25
Std dev 23.50 187.39
System  41
4C04 518.68 3517.14 2.57 41.58
4C05 510.62 3756.63 2.67 40.46
4C06 587.18 4622.08 2.91 38.09
Average 538.83 3965.28 2.72 40.04
Std dev 42.07 581.27
(36 - T  B l l t l
I 8/99 3056B-37 iB
- BOZEMAN