Theses and Dissertations at Montana State University (MSU)
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Item Ice-templated ceramic-metal composites modified by interfacial metal aluminates(Montana State University - Bozeman, College of Engineering, 2024) Marotta, Amanda Rose; Chairperson, Graduate Committee: Stephen W. Sofie; This is a manuscript style paper that includes co-authored chapters.Interpenetrating phase (3-3) composites consists of two phases which are fully percolating throughout one system. Research efforts have been made towards routes to fabricate these composites that will allow for them to be utilized for applications like heat spreaders and leading-edge parts. Freeze-tape casting offers a potential avenue for developing 3-3 composites. The system can exhibit complete, long-range alignment through freeze-tape casting, in which both phases of the composite will be in constant periodicity of one another. To explore the potential of such ordering in 3-3 composites, ceramics, such as, yttria- stabilized zirconia (YSZ), alumina (Al 2 O 3) and zirconium diboride (ZrB 2) were freeze-tape casted and sintered to allow for second phase incorporation. Second phases, like copper (Cu) and silicon carbide (SiC) were utilized, so that ceramic-metal (cermet) freeze-tape casted composites and ultra-high temperature ceramic (UHTC) freeze-tape casted composites could be characterized. Initial composite property predictions were made using rule of mixtures (ROM). The work contained in this dissertation demonstrates that freeze-tape casted 3-3 composites can exhibit novel 3-axial anisotropic thermal behavior, and that, by ordering the percolating phases, high-temperature thermal behavior may be enhanced. This work, also, demonstrated that ceramic-metal interfaces are fragile, exhibiting thermal stress at the interface upon thermal cycling. Fostering interfacial adhesion between metal and ceramic phases is a primary tool for manipulating cermet properties. Common approaches to ceramic-metal joining include metallization and active brazing techniques. Though improvements in mechanical properties are notable, the functional capabilities can be sacrificed. To overcome these limitations, a novel approach, via a metal aluminate (copper aluminate), has been utilized to alleviate thermal stress along a ceramic-metal interface, and maintain adhesion of the ceramic-metal up to 100 psi. Mechanistically, it was not well- understood, as to what role copper aluminate played in modifying ceramic-metal interfaces. Chapter 5 of this work elucidates copper aluminate's role in fostering a ceramic-metal interface. By analyzing the surface and cross-sectional features of the cermet, it is discovered that through the formation of copper aluminate, porosity/roughness occurs to the bulk ceramic, allowing avenues for the metallic phase to penetrate through the thickness, fostering a mechanical interlocked joint.Item Effect of process variables on the uncured handleability and formability of stretch broken carbon fiber(Montana State University - Bozeman, The Graduate School, 2022) Rezaul, Riad Morshed; Chairperson, Graduate Committee: Cecily A. RyanCarbon fiber is a high-performance reinforcing material used extensively in aerospace composites. Although carbon fiber is used in both continuous and discontinuous form, the continuous carbon fiber is limited by its inability to stretch due to its low strain to failure during manufacturing structures with complex geometries. Stretch broken carbon fiber (SBCF) is a type of discontinuous and aligned carbon fiber which has the potential to solve this limitation of inextensibility of its continuous counterpart. The discontinuous nature of SBCF enhances its stretchability making this material a prime candidate for manufacturing parts with complex curvatures. SBCF is generated by stretching the fibers using a pair of differentially driven rollers, which breaks the fibers at their intrinsic flaws. Although SBCF can be stretched due to being discontinuous, it compromises the tensile strength due to the lack of fiber continuity. Therefore, a polymeric coating known as sizing is applied to the SBCF to reconstruct its tensile strength. In the context of SBCF production, sizing serves two important functions. Firstly, sizing provides uncured carbon fiber the desired handleability and back-tension ability. Secondly, sizing enhances the formability of SBCF, which is a defined as the ease at which a material can be formed into a desired shape without failure. The goal of this work is to investigate the effect of process variables on the generation of stretch broken carbon fiber with consistent and repeatable material properties. The stretch broken carbon fiber research group at Montana State University (MSU) has developed a stretch breaking machine known as 'Bobcat' to generate single tow MSU SBCF. The noteworthy process variables related to MSU SBCF production includes sizing deposition on the tow, stretch ratio, nip force, line speed, fiber length distribution, and tow tenacity. Target amount of sizing deposition on MSU SBCF tow was achieved by choosing an appropriate sizing bath. A temperature-controlled tow tenacity result suggests that MSU SBCF possesses adequate handleability, back-tension ability and formability. MSU SBCF also shows a narrow fiber length distribution and relatively short mean fiber length which indicate improved formability. Reproducibility of these results were observed in the replicate batches of MSU SBCF. Suitable stretch ratio and nip force regimes were identified to optimize MSU SBCF production.Item Forming properties of stretch broken carbon fiber for aircraft structures(Montana State University - Bozeman, College of Engineering, 2023) Nold, Dalton Bradley; Chairperson, Graduate Committee: Dilpreet S. Bajwa; Douglas S. Cairns (co-chair); This is a manuscript style paper that includes co-authored chapters.Continuous carbon fiber is known to be a superior material for its strength, stiffness, and high strength-to-weight ratio and is often incorporated in aerospace composites. A challenge, however, is that it's not versatile in forming deep drawn geometries, which require convoluted manufacturing techniques resulting in expensive components. To overcome this, a type of carbon fiber with a random discontinuous fiber alignment called stretch broken carbon fiber (SBCF) is proposed. SBCF has potential to form parts with complex geometries with comparable or better mechanical properties to that of continuous carbon fiber. Montana State University (MSU) developed its own version of SBCF manufacturing processes, and research is being conducted to understand how SBCF prepreg tows react to stretch drawing at elevated temperatures using aerospace-grade epoxy resin systems. Currently, several new methods have been proposed to rapidly test these materials. This research revealed that SBCF forms with greater ease than continuous carbon fiber and is expected to substantially reduce manufacturing times for aircraft structures. To comprehend the material's behavior, simple tensile tests were coursed to understand how gauge length and temperature affected the peak loads when compared to continuous carbon fiber. It was discovered that on average, SBCF experienced stresses that were ten times less than continuous fibers. Additional tensile tests were conducted at elevated temperature to determine the true stress versus true strain. These tests are particularly important because they represent the material's most accurate mechanical properties. The results led to the discovery that SBCF experienced strain softening behavior. Furthermore, a series of forming tests using a novel "forming fixture" revealed that increasing the gap lowered the peak forming loads while the plunger geometry had little to no effect on peak forces at both room and elevated temperatures.Item Application of functionalized cellulose nanocrystals to improve their dispersion in polymer matrix and enhance the thermo-mechanical properties of polymer composites(Montana State University - Bozeman, College of Engineering, 2023) Chanda, Saptaparni; Chairperson, Graduate Committee: Dilpreet S. Bajwa; This is a manuscript style paper that includes co-authored chapters.In the past few years, Cellulose nanocrystals (CNC) and its derivatives are exploited as potential bio-based nanofillers for functional polymer composites. The main challenge for manufacturing CNC-based composites is to disperse CNC uniformly in the hydrophobic polymer matrix. The hydrophilicity of CNC hindered their uniform distribution in the matrix and reduced the overall thermal, mechanical, and physical properties of the composite system. To overcome this challenge, several methods have been developed, such as physical and chemical modification of CNC. Also, polymer-based composites are highly flammable in nature and can cause severe life-threatening incidence. The flame-retardants available commercially should be added to the composite for a very high add-on% and toxic in nature, which is not eco-friendly and can be dangerous for humans. In this study, two critical research gaps are addressed: 1) uniform dispersion of CNC in a hydrophobic matrix, and 2) improving fire-retardancy of polymer composites by using non-toxic inorganic oxides. In the first part, a chemical compound, aminosilane was used as a dispersing agent for CNC in polyethylene oxide (PEO) based composite films and their thermo-chemical properties were analyzed. In the next part, the silanated CNCs are coated with nano ZnO and nano B2O3 and added as a functional filler to manufacture high density polyethylene (HDPE) based composites. The ZnO coated composites showed a significant improvement in thermo-mechanical properties of the composites even at a low add-on%, due to the smaller size and higher surface area of nano ZnO. The lignin containing CNC (LCNC) was also used as a functional additive along with nano ZnO and B2O 3. The hydrophobic character of lignin could not improve the dispersion of LCNC in the HDPE matrix because of the reduction of the aspect ratio and aggregate formation of LCNC/inorganic oxides during freeze drying. The role of the new age material graphene quantum dots (GQD) as a dispersing agent for CNC was also exploited. The CNC/GQD inclusion complex showed excellent dispersion behavior in HDPE matrix along with the significant improvement in thermo-mechanical properties of the composites, even at very low add-on% of GQD. The preliminary idea of using CNC/GQD inclusion complex as an energy storage device was also developed. Overall, the current work addresses the two main challenges which hindered the functional application of CNC based polymer composites and developed safe, effective, and eco-friendly methods to overcome those challenges. CNC based polymer composites have strong potential to be used in various industrial applications from fire-retardant material to energy storage device.Item Forming evaluation metrics and methods for complex stretch broken and continuous carbon fiber parts(Montana State University - Bozeman, College of Engineering, 2023) Dube, Madison Eve; Chairperson, Graduate Committee: Cecily RyanCarbon fiber composites are an ideal material for aircraft structures due to their light weight and high strength and stiffness. Traditional continuous carbon fiber composites are limited by their ability to form into complex geometric features as they have minimal abilities to stretch into a mold. Stretch broken carbon fiber is discontinuous which allows for the different tows of carbon fiber to slip relative to each other allowing for laminate displacements unattainable to continuous carbon fiber. In order to develop and improve stretch broken carbon fiber manufacturing processes, a method is developed herein to analyze the forming quality of a complex carbon fiber part. This method quantifies common qualitative forming metrics by measuring, evaluating, and scoring carbon fiber defects including: bridging, wrinkling, variation in thickness, forming depth, corner thinning and thickening, resin pooling, and additional texture defects. The scores produced from evaluating the various forming metrics on formed carbon fiber parts are assembled in a weighted matrix to produce an overall forming score. This forming evaluation method is demonstrated on three different geometric mold designs to assess that it is quantitative, repeatable, accounts for many carbon fiber defects, and accounts for discrepancies between the formed part and the designed part. This method was also tested on different carbon fiber prepreg materials: MSU SBCF/Cycom 977-3 resin from Solvay, MSU SBCF/Hexcel 8552, and Hexcel IM7/8552. Through testing, the method is found to have achieved the method design goals as well as ascertaining areas of improvement for MSU SBCF prepreg which is still under development. Results show that stretch broken carbon fiber and traditional continuous carbon fiber achieve similar overarching forming scores, but outperform one another in different category metrics. MSU SBCF has higher scores in corner thickening and resin pooling; continuous carbon fiber has higher scores in wrinkling and bridging. The method forms the foundation to evaluate layup practices and autoclave cure cycles when systematically applied in a process development setting. This method is also extendable to dissimilar geometric part types with modifications in suitable metrics.Item Biodegradable composite hydromulches for sustainable organic horticulture(Montana State University - Bozeman, College of Engineering, 2023) Durado, Andrew Dalton; Chairperson, Graduate Committee: Dilpreet S. BajwaIn agriculture, mulch helps retain soil moisture and temperature while preventing weed growth. The most common material used for commercial mulching is low-density polyethylene (LDPE). At the end of the growing season, this plastic is typically buried or burned, causing a negative impact on the environment. This project aims to develop an alternative to LDPE mulch that is acceptable for organic farming and biodegradable. The tested hydromulch (HM) treatments contain a mixture of paper pulp, wood fiber, or hemp hurds combined with a tackifier and water. The tackifiers evaluated were guar gum, psyllium husk, and camelina meal, at various concentrations. These treatments were tested for tensile strength, puncture resistance, rain fastness, density, soil adhesion, porosity, and C:N ratio. The results have shown that samples containing tackifiers outperformed the control that contained no tackifier in the strength tests but not in the rain fastness or soil adhesion tests. Paper was the best fibrous material and guar gum was the top performing tackifier. When tackifier blends were considered, an interaction between two tackifiers occurred resulting in a decrease in strength. Blends containing wood fiber and hemp hurds did not show promising results. The puncture resistance of all mulches significantly decreased at 50% moisture level regardless of tackifier type. Some formulations performed well and could be promising in future field trials. The next step will be to examine these formulations outdoors in large-scale field studies.Item Influence of pretreatment, lignin extraction, and chemical modification on lignin properties and the performance of lignin-formaldehyde resins and lignin-PLA composite materials(Montana State University - Bozeman, College of Engineering, 2022) Saulnier, Brian Keith; Chairperson, Graduate Committee: David Hodge; This is a manuscript style paper that includes co-authored chapters.Bio-ethanol can be produced from lignocellulosic biomass in a biorefinery as part of a three step process, a chemical or mechanical pretreatment, enzymatic hydrolysis of the cell wall, and fermentation of these sugars to ethanol. One of the byproducts of this process is lignin, a complex biopolymer composed of a heterogeneous aromatic structure. Lignin is often burned to provide energy for the biorefinery. Incorporating lignin into higher-value products is crucial to the viability of the biorefinery process and the full utilization of the renewable carbon contained in biomass. Challenges to the inclusion of lignin in value-added products include recalcitrance of the cell wall to deconstruction and lignin extraction, heterogeneity of the lignin chemical structure, polydisperse molecular weight distributions, and low reactivity. In this thesis we address these challenges by using feedstock selection, selection of pretreatment and lignin extraction process conditions, lignin fractional precipitation, and direct chemical modification of lignin. Chapter 1 provides an overall introduction and background of previous work. Chapter 2 uses a diverse panel of corn stover genotypes subjected to dilute acid pretreatment using a variety of process conditions. The response of the biomass to pretreatment was characterized with special attention given to glucose hydrolysis yields and p-coumarate (pCA) content. Chapter 3 uses a single corn stover source pretreated using a variety of dilute acid conditions followed by two different lignin extraction methods. The influence of pretreatment and lignin extraction conditions on lignin properties was characterized with focus on lignin pCA content. This study found that lignin-formaldehyde resins using lignin from optimized process conditions achieved lap shear strengths higher than conventional phenol-formaldehyde resins. Chapter 4 addresses lignin polydispersity and heterogeneity using the fractional precipitation of lignin from formic acid liquors to obtain differing molecular weight lignin fractions while allowing for successful enzymatic hydrolysis of cellulose. Chapter 5 uses fractional precipitation of corn stover alkali liquors along with modification using propylene carbonate to obtain a panel of multi-component biopolymer fractions for manufacture of biopolymer-PLA composite materials. These materials were fully characterized finding materials made with modified biopolymers exhibited better lignin dispersion, and improved thermal and mechanical properties.Item Forming parameters and quantification of continous and stretch broken carbon fibers(Montana State University - Bozeman, College of Engineering, 2021) Janicki, Joseph Charles; Chairperson, Graduate Committee: Dilpreet S. Bajwa; This thesis contains two articles of which Joseph Charles Janicki is not the main author.Continuous carbon fibers are premium reinforcing material for aerospace composites. Carbon fiber reinforced polymers are five times stronger than steel and twice as stiff, making it an ideal candidate for structural aircraft components where weight is an important factor. The challenge with continuous carbon fibers is their difficulty to form deep drawn parts requiring intricate manufacturing techniques that increase manufacturing time, cost, and material waste. An alternative to continuous carbon fibers is stretch broken carbon fiber (SBCF). SBCF is a form of aligned discontinuous fiber, it has been proposed as an alternative to overcome this formability challenge. SBCF provides flexibility to form complex shapes while maintaining comparable strength and stiffness. A variety of testing methods have been developed to study both the ability of SBCF to form over traditional continuous carbon fiber and how different iterations of SBCF perform against each other. These include testing carbon fiber tows in tension on a universal test stand as well as designing and creating a forming tool that tests resin impregnated tows under different geometry conditions and temperatures. Tensile properties of both a continuous tow and a SBCF tow were evaluated at different gauge lengths and temperatures. It shows that SBCF tow maximum load increases as the gauge length decreases as well as elevated temperature has a clear effect on the tensile properties when fiber continuity is considered. Cross-sectional areas of continuous and SBCF tows were calculated using both areal weight and scanning electron microscopy showing that in general continuous fiber tows have a larger cross-section than SBCF. Using a forming fixture to test samples, results were statistically analyzed in order to display the significance of geometry and temperature on the maximum forming load of different fibers. The suite of testing and results indicate that in general SBCF maintains superior formability to that of continuous fibers. Overall lower maximum force is required for SBCF to form into deep drawn shapes. This supports their ability to be used more readily in complex aircraft structure while minimizing the disadvantages posed by traditional carbon composites.Item Fiber shape effects on the compressive strength of unidirectional carbon fiber composites: a computational study(Montana State University - Bozeman, College of Engineering, 2020) Clarke, Ryan; Chairperson, Graduate Committee: David A. MillerThe tensile strength tends to be much higher than the compressive strength for carbon fiber reinforced polymer composites because of a change in failure modes. Current research activities are looking at novel precursors for reducing overall costs of carbon fiber production. The potential cost savings in new precursor carbon fiber make it economically feasible to use in large structural components. Some fiber precursors and manufacturing methods produce carbon fibers that have a kidney-shaped cross-section whereas traditional carbon fiber is circular. The aim of this study is to investigate the differences in compressive failure responses between fiber shapes in carbon fiber composites. A finite element micromechanical model was developed in ABAQUS of a single carbon fiber embedded in a square matrix with periodic boundary conditions. Two fiber cross-sectional geometries were examined: circular and kidney shaped. Three factors that affect the compressive failure response of carbon fiber reinforced polymers were investigated. These include fiber misalignment, volume fraction, and multiaxial loading. The results showed negligible differences between the compressive failure response of fibers with different cross-sectional shapes. Compressive strength was shown to have a decaying sensitivity to increasing fiber misalignment. Decreasing the volume fraction did decrease the compressive strength but also increased the compressive failure strain. In addition, adding in-plane shear loads proved detrimental to the compressive load-carrying capacity of a composite structure. This research showed minimizing fiber misalignment in manufacturing processes is only beneficial for high tolerance processes. In addition, decreasing volume fraction could be beneficial for highly flexible structures. Finally, the results demonstrated the need to minimize multiaxial loading for optimal composite compressive response.Item Developing a load acquisition system for a multiaxial test frame(Montana State University - Bozeman, College of Engineering, 2019) Carpenter, Aaron James; Chairperson, Graduate Committee: David A. MillerMaterial testing has traditionally been completed by using a uniaxial load frame which isolates a single stress component. Engineers however, design components for applications in a multi-axial world to withstand stress in multiple directions. The In-Plane Loader (IPL) at Montana State University expands the realm of material testing to three degrees of freedom within a two-dimensional plane. Applications of the IPL include composite material testing and experimental validation of constitutive models in multiple axes. The multi-axial test frame has been in place at MSU for several years. One of the primary challenges associated with the IPL is its ability to accurately measure multi-axial load components. The purpose of this work was to develop and validate an updated multi-axial load acquisition system for the IPL. The procedure included design, manufacture, implementation, and validation of the system. Validating the system in multiple axes required isolating single stress components along each of the planar axes. Tension tests were completed to isolate the vertical component, and shear tests were completed to isolate the horizontal component. Each of the results were compared to results of standardized test procedures designed to isolate their respective stress components. Digital image correlation was implemented as a non-contact method of measuring displacement for the testing procedures. The data collected in this study provides confidence in the ability to measure multi-axial loading in combination with digital image correlation to expand the capabilities of multi-axial testing. The system provides the ability to study load dependent failure of materials as well as displacement dependent failure. The information presented provides an understanding of challenges associated with multi-axial testing which hopes to assist in the development of future multi-axial test frames.