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Item Characterization of multi-physics aging effects on the thermomechanical viscoelastic response of ultra high molecular weight polyethylene fiber reinforced composites(Montana State University - Bozeman, College of Engineering, 2024) Weaver, Jonmichael Andrew; Chairperson, Graduate Committee: David A. MillerUltra High Molecular Weight Polyethylene (UHMWPE) fiber reinforced composites have a high strength-to-weight ratio and are gaining attention as a material of choice for specialized applications subjected to extreme environmental conditions. Users value the water-repellent, lightweight, and flexible nature of the material for applications where weight is crucial. Marine, aerospace, and alternative energy sectors are exploring UHMWPE fiber reinforced composites for specialized applications in demanding environments where strength, flexibility, and weight efficiency are important design criteria. The viscoelastic and hydrophobic nature of UHMWPE makes it an attractive replacement for Kevlar® in ballistics protection shields and other industrial applications, providing similar performance while achieving upwards of 40% reduction in weight. However, the durability of UHMWPE composites under real-world aging conditions remains insufficiently examined. This research investigates how the viscoelastic properties of UHMWPE fiber reinforced composites, created through various manufacturing techniques, are altered after exposure to harsh conditions including immersion in water, temperature variations, humidity, and UV exposure. Additionally, the composites were irradiated with: X-rays, gamma-rays, and neutrons. After exposure to adverse environments, the thermomechanical viscoelastic response was characterized through Dynamic Mechanical Analysis (DMA). Surface morphology was evaluated using a field emission scanning electron microscope. DMA revealed an increase in the storage modulus with aging; however, elevated temperature creep tests showed that UV and hygrothermal aging had a higher creep compliance and decreased the ability of the composite to recover strain after unloading. Both single layer and pressed UHMWPE panels showed an increase in weight after submersion in water. Distilled water resulted in a faster rate of hydrolysis in the matrix than did salt water. The UV, gamma-ray, and neutron environments caused the composites to become brittle and yellow through chain scission and crosslinking, whereas the X-ray radiation exposure did not cause a measurable effect. Analysis on the surface of these composites after aging suggested the matrix protects these fibers from damage in harsh environments. Synthetic rubber matrix materials aged at a faster rate than the polyurethane rubber matrix materials. Increasing the strain rate showed an increase in moduli response during tensile DMA. These results quantify the limitations and strengths of this material for future models to accurately predict the lifespan and expand the application of this performance material in extreme environments to ensure safety for applications ranging from extreme sports to aerospace.Item Value-added composite bioproducts reinforced with regionally significant agricultural residues(Montana State University - Bozeman, College of Engineering, 2018) Solle, Matthew Arthur; Chairperson, Graduate Committee: Cecily Ryan; Jesse Arroyo, Stephan Warnat, Macdonald Burgess and Cecily Ryan were co-authors of the article, 'Evaluation of locally sourced agricultural residue in composites' submitted to the journal 'Composites science and technology' which is contained within this thesis.Biopolymers, such as polyhydroxybutyrate-co-hydroxyvalerate (PHBV), combined with natural fiber into biocomposites have potential as sustainable alternatives to traditional plastics and composites for which recycling is challenging. The addition of natural fibers, such as hemp, kenaf, and jute can increase the stiffness and strength of biopolymers at low weight and cost without compromising composite biodegradability. Because production of many natural fibers is limited by climate or geography, local and regional fiber sources collected as residues from agricultural crop production have potential to further reduce composite environmental impact by reducing embodied energy related to transportation and fiber cultivation. In this study four agricultural residue fibers (AF) were assessed: (i) hollow stem wheat, (ii) solid stem wheat, and (iii) barley as regionally significant food crop residues compared to (iv) hemp residue from seed and oil production as an industrially relevant control. These fibers were compounded into PHBV composites at fiber weight fractions of 0%, 10%, 20%, and 30%. Two fiber compatibilizing treatments were investigated for their potential to enhance the mechanical performance of AF-PHBV composites: (i) silane vapor deposited at room temperature and (ii) PHBV grafted to the fibers using reactive extrusion (gPHBV). Mechanical properties including flexural modulus and ultimate flexural strength were used to evaluate the impact of fiber fraction and treatments on biocomposites. Statistical analysis from our design of experiments indicated that some combinations of fiber, weight fraction, and treatment clearly outperformed others. In particular, samples with 30% silane treated hemp had the highest modulus and high flexural strength, while 30% gPHBV hemp had high modulus and the highest strength. Among residue composites, hollow stem wheat is most comparable to hemp, with similar modulus but lower flexural strength in treated high fiber samples. Solid stem wheat and barley composites generally had lower modulus, lower strength, and less consistent mechanical properties. Increasing fiber fraction consistently increased flexural modulus. Grafted samples had inconsistent flexural strength due to deleterious effects to the gPHBV matrix, as observed with scanning electron microscopy and differential scanning calorimetry. The mechanical properties of the different AF-composites occupy a similar application space, indicating potential for robust composite processing using AF.Item An acoustic emission and hygrothermal aging study of fiber reinforced polymer composites(Montana State University - Bozeman, College of Engineering, 2019) Newhouse, Kai Jeffrey; Chairperson, Graduate Committee: David A. MillerFiber reinforced polymer matrix composites are a premier choice for offshore wind turbines and Marine Hydro-Kinetic Devices, which operate in harsh and isolated marine environments. These factors combined with decades long target service life make imperative the understanding of damage mechanisms and the environmental effects thereof. Acoustic emission monitoring is a research technology that uses specialized sensors to detect transient elastic waves in a material which originate from damage sources. Waveform parameters have been correlated with different damage mechanisms in fibrous composites. A diverse set of fiber-matrix combinations configured into a variety of layups totaling more than 30 laminates were mechanically tested in quasi-static uniaxial tension while monitoring acoustic emission. A subset of these materials was aged prior to testing in an artificial marine environment by soaking in a water bath of simulated seawater at 50 degrees Celsius. Various acoustic emission waveform parameters were investigated with respect to expected damage between layups and possible material-based differences. Among the conditioned material set, mechanical changes from moisture absorption shows mixed levels of degradation among different material systems. Moduli were generally unaffected with a few minor decreases. Strengths were reduced by as much as 41%, and failure strains fell as much as 47%. From acoustic emission investigation, good correlation is found between Fast Fourier Transform peak spectral frequency bands and expected damage mechanisms between layups. Material based peak frequency differences are found exclusively in interphase failures (de-bond and fiber pullout). Layup-based correlations in conjunction with elastic wave theory were used to put forth new frequency band ranges associated with damage types.Item Manufacturing reliability for C-channel composite beams(Montana State University - Bozeman, College of Engineering, 2014) Bauer, Michael Wayne; Chairperson, Graduate Committee: Douglas S. CairnsA new manufacturing method has been developed for fabricating c-channel composite beams. The beams are to be used as test articles in four point bending tests. The motivation behind this thesis is to study the effects that specific manufacturing parameters have on the resulting amounts of porosity and fiber volume in these three-dimensional sub-scale structures. The parameters considered are number of layers of flow media, fabric architecture, flow rate of the resin, temperature of the resin, and level of vacuum pressure used. The manufacturing parameters were varied in a 1/2 factorial design of experiments where sixteen beams were manufactured, all with varying values for each parameter. A taguchi design of experiments was also formed to provide a comparison. The resulting average porosity percentages and fiber volume percentages were then determined for every beam. In addition, compression and tension tests were conducted to find the average maximum stresses for each. Once all the data had been gathered an Analysis of Variance (ANOVA) study was conducted to determine the effects and their levels of significance. It was found that the level of vacuum pressure has the most significant effect on the porosity while the fabric architecture has the most significant effect on the fiber volume. Overall, every parameter has some sort of quantifiable effect on porosity and fiber volume. There are also significant two and three way interaction effects present for each. Additionally, the 1/2 factorial design seemed to provide more accurate results compared with the taguchi design, which was inherently not comprised of data with a normal distribution and does not include interaction effects. Regression models were developed for the output levels of porosity and fiber volume. This allows manufacturers to create these beams with predetermined output levels for each and can improve testing capabilities. Also, using two layers of flow media greatly improved the consistency of the beams, while reducing porosity and slightly reducing fiber volume percentage. It is recommended to further implement the use of two layers of flow media into large sub-scale structures and potentially full scale turbine blades.Item Effect of fiber diameter on stress transfer and interfacial damage in fiber reinforced composites(Montana State University - Bozeman, College of Engineering, 2011) Peterson, William Matthew; Chairperson, Graduate Committee: Christopher H. M. JenkinsIn this work, the effect of fiber diameter upon the strength, stiffness, and damage tolerance of a fiber-reinforced polymer composite laminate structure was investigated. Three cases were considered, in which the fiber diameters of 16, 8, and 4 microns were used. A fiber volume fraction of 32% was assumed in each model. Micromechanical, shear-lag, and progressive damage analyses were performed using finite element models of the structure, which was subjected to tensile loading in the fiber direction. Fiber-matrix load transfer efficiencies and the stress distributions near broken fibers within the composite structure were investigated and results compared for each fiber diameter. In addition, the effect of fiber diameter upon the initiation and evolution of fiber-matrix interfacial damage and debonding was studied using cohesive interface elements. For a specified volume fraction and load condition, as the fiber diameter was decreased the load transfer efficiency and effective stiffness of the broken fiber model increased. Also, as the fiber diameter was decreased, the initiation of damage at the fiber-matrix interface occurred at greater stresses and the subsequent growth of damage was less extensive. These results indicate that, for the same total mass, the performance and damage tolerance of composite materials may be enhanced simply by using smaller diameter fibers.Item Fatigue performance of macro-fiber piezoelectric composite actuator with respect to variable beam geometry(Montana State University - Bozeman, College of Engineering, 2012) Rosatti, Lyric Michael; Chairperson, Graduate Committee: David A. MillerThis study is an investigation into the reliability and performance over the lifetime of the piezoelectric fiber composite, macro fiber composite (MFC), with respect to variable beam geometry. MFC's are a class of smart structure utilizing the piezoelectric effect. The MFC is a thin flexible composite system that can be laminated to surfaces or embedded in classic composite structures for actuation and sensing. These piezocomposite structures are rectangular patches made of Lead-Zirconium-Titinate (PZT) piezoceramic fibers, copper-clad polyimide film, and epoxy. MFC's were originally developed at NASA Langley Research Center and are now commercially available from a single manufacturer. In this study, lifespan and performance were characterized by using the MFC as an actuator to impart deflection in a substrate. This structure is referred to as a Unimorph. The beam geometry affects the bending stiffness of the beam, and thus affects the reaction of the MFC. The only free geometrical dimension in this study was beam height. The unimorph was actuated cyclically by an electrical field of 3E+6 volts per micron at a frequency of 3750 Hz. Expected cycles to failure was 10 9 cycles. The test specimens consisted of cantilevered A2 tool steel beams, with six discrete beam heights, and an MFC patch laminated to one surface by a two-part epoxy. Beam tip displacement measurements were taken using a laser displacement sensor as an indication of cyclical performance over time. The beams were cycled until failure or 10 9 cycles for all beam geometries. The results of the experiment indicate a severe drop off in life with an increase of work energy out of the system. This is a function of the ratio of beam stiffness to MFC stiffness. After a break-in period of less than 250E+6 cycles, no significant degradation in operational performance was indicated by the recorded tip displacement despite an immense amount of crack propagation in the piezoceramic fibers. The results of this testing can be used in designing piezoelectric actuators and as a basis for further study of MFC's.Item Macrofiber piezoelectric composite for lunar exploration actuator(Montana State University - Bozeman, College of Engineering, 2010) Henslee, Isaac Andrew; Chairperson, Graduate Committee: David A. MillerUnderstanding the nature and location of water and other resources on Earth's Moon is an essential component to the National Aeronautics and Space Administration's (NASA) space exploration efforts. To aid in these exploration efforts, an investigation into lightweight and reliable materials for a lunar valve actuator design has lead to characterizing the lifetime performance of the piezoelectric fiber composite, macro fiber composite (MFC). MFC's are thin rectangular patches made of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate fibers and are commercially available. As a basis for this consideration, the useful life of the MFC is being characterized to determine the effect of temperature on the performance of the material as it is fatigued by cyclical piezoelectric excitation or actuation. The test specimen consist of the MFC laminated to a cantilevered stainless steel beam using epoxy and is actuated at the first resonant frequency of the beam laminate by the cyclic application of 1000 volts. Strain and beam tip displacement measurements are used as a basis for determining the performance of the MFC as it is cyclically actuated under various operating temperatures. The temperature of the beam laminate is held constant during cyclic actuation and cycled to failure or 250 million cycles, to determine the useful life of the MFC over a temperature range from -15°C to 145°C. The results of the experimentation efforts show a strong temperature dependence on operational life for the MFC. No significant degradation in operational performance was identified thru monitoring of the MFC, as the MFC was cyclically actuated up to the point of failure, regardless of temperature or actuation cycle. The results of the experimental testing can be used to better inform designs, such as actuators, using MFC in environments where operational temperatures differ from standard laboratory temperatures, as well as, to better design temperature controlled environments where MFC's are used as actuators.