Engineering Commons^™

Numerical Simulation Of Laser Induced Elastic Waves In Response To Short And Ultrashort Laser Pulses., Alireza Zarei

All Dissertations

In an era of intensified market competition, the demand for cost-effective, high-quality, high-performance, and reliable products continues to rise. Meeting this demand necessitates the mass production of premium products through the integration of cutting-edge technologies and advanced materials while ensuring their integrity and safety. In this context, Nondestructive Testing (NDT) techniques emerge as indispensable tools for guaranteeing the integrity, reliability, and safety of products across diverse industries.

Various NDT techniques, including ultrasonic testing, computed tomography, thermography, and acoustic emissions, have long served as cornerstones for inspecting materials and structures. Among these, ultrasonic testing stands out as the most prevalent method, …

Microscale Transverse Compression Modeling: A Comparative Study Of The Analytical Mac/Gmc Methods To Experimental Results, Emily Zeitunian

Dissertations, Master's Theses and Master's Reports

Composite materials require a multi-scale approach to fully understand its behavior. At the micro level, material behavior analysis is conducted most often using numerical or analytical approaches. These models, however, require validation from experimental data to ensure material predictions are accurate. This study compares a semi-analytical micromechanical analysis tool, MAC/GMC, to experimental results of in-situ microscale transverse compression testing conducted at AFRL facilities. Effective properties, stress-strain curves, stress and strain fields, and damage predictions are compared with experimental outputs. Both generalized method of cells (GMC) and high-fidelity generalized method of cells (HFGMC) theories implemented within MAC/GMC show results that agree …

Solvent Analysis Of Phenolic Resin Glass Fiber Reinforced Prepreg During Out-Time, Sixin Zhai, Crystal Ipong

Materials Engineering

Phenolic resin glass fiber reinforced prepregs are highly suitable for airplane interior components due to their high fire resistance, high temperature performance, and low-density characteristics. Safran Cabin seeks to improve their storage of the phenolic resin prepreg during their manufacturing process. The issues the company faces are the occasional delamination of prepreg laminas or the loss of tackiness rendering the lamina unfit for use. The area of investigation was determining the weight loss of volatiles during out-time. The term “out-time” consists of the time the prepreg experiences in transit, on the shop floor, and in short-term temperature-controlled storage. Simulated storage …

Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts

Theses and Dissertations

Hybrid composites require further study and testing for future use in various fields. This study focuses on simulating a Hybrid Composite using IM7-977-3 laminae with steel foils in Abaqus under bolt loading by using Hashin and Tsai-Wu failure criterion. Initial simulations contain only the IM7-977-3 composite with cohesive layers. Foil samples were then tested for accurate material properties from which the simulations were then updated to include steel foils. The two models show that Tsai-Wu failure criterion, while great for anisotropic material in tension, does not prove accuracy around the hole of the composite material which is in compression. Hashin …

Interlaminar Damage Detection In Composite Materials, Hariharan Rangarajan

Williams Honors College, Honors Research Projects

Using ceramic matrix composites (CMCs) for high-temperature applications in jet engines increases durability and reduces weight and cooling requirements resulting in improved efficiency and fuel savings. Understanding, detecting, and monitoring different types of damage is essential to achieve optimal performance of CMC components. The Direct Current Potential Drop (DCPD) method is a non-destructive technique of estimating damage in composite materials.

DCPD technique works by measuring nodal potential differences when current is flown through the material. Direct current spreading in different woven and laminate composites is modeled to follow a ladder resistor network in which the nodal voltages decrease exponentially as …

Form Stable Phase-Change Materials, Russell Dent, Marjan Kashfipour, Nitin Mehra, Jiahua Zhu

Williams Honors College, Honors Research Projects

This work investigates the use of two different polyols, xylitol (Xyl) and erythritol (Ery), in conjunction with boron nitride (BN) aerogels, for the purpose of creating thermally conductive composites. While the BN filler in Xyl composites achieved a high anisotropic thermal conductivity of up to 4.53 W/m-K at 18.2 weight percent filler loading, they do not exhibit good phase-change material qualities due to a low solidification enthalpy even at low cooling rates. Alternatively, the BN-Ery composites have shown promising results with a solidification enthalpy of 225.14 J/g and a melting enthalpy of 385.84 J/g at a heat rate of 5 …

Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh

Doctoral Dissertations

Metamaterials (MMs) are nanocomposite materials consisting of metal-dielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications …

Synthesis And Behavior Characterization Of Multi-Scale Hierarchical Structured Composites, Jacob M. Mayfield

Electronic Theses and Dissertations

The purpose of the synthesis of a multi-scale hierarchical composite material was to create a material with a high specific strength, a low mass, and high strength material. To achieve this the material categorization of the Formlabs Tough V2 resin was conducted. The resin was used in the construction of a bio-mimicry diamond lattice structure. The structure was subjected to compression testing to characterize the material properties. The Tough V2 resin structure combined with cellulose created a multi-scaled material on Macro and Micro levels to show the bio-inspired design to increase the material properties in a favorable manor. The Tough …

In Mold Flow Of Long Fibers In Compression Molding Process, Gleb Meirson

Electronic Thesis and Dissertation Repository

Long Fiber Thermoplastics (LFT) are promising new materials with high physical properties and low density. These high properties are obtained by embedding very long fibers (~100 mm) into a thermoplastic matrix. Such a high fiber length dictates the use of a compression molding process for manufacturing as the length of discontinuous fibers in injection molding is limited by pellet length.

LFT composites are of great interest for the automotive industry. These materials are already used in some interior and exterior car parts such as bumpers, seat structures, door module etc. This research is inspired by the desire to manufacture load …

Fatigue Behavior Of Im7/Bmi 5250-4 Composite At Room And Elevated Temperatures, James T. Tipton

Theses and Dissertations

The tension-tension fatigue and tension-compression fatigue behaviors of the IM7/BMI 5250-4 composite were investigated. The tension-tension fatigue of the composite with 0/90 and ±45 fiber orientations was studied at 23, 170, and 190°C. The tension-compression fatigue of the composite with 0/90 fiber orientation was examined at 23°C. The tensile and compressive properties of the composite were also evaluated at room and elevated temperatures for both 0/90 and ±45 fiber orientations. Elevated temperature had little effect on the tensile properties of the 0/90 fiber orientation, but strongly influenced the ±45 tensile properties as well as the compressive properties of both fiber …

Solution To Certain Problems In The Failure Of Composite Structures, Jonathan Goodsell

Open Access Dissertations

The present work contains the solution of two problems in composite structures. In the first, an approximate elasticity solution for prediction of the displacement, stress and strain fields within the m-layer, symmetric and balanced angle-ply composite laminate of finite-width subjected anticlastic bending deformation is developed. The solution is shown to recover classical laminated plate theory predictions at interior regions of the laminate and thereby illustrates the boundary layer character of this interlaminar phenomenon. The results exhibit the anticipated response in congruence with the solutions for uniform axial extension and uniform temperature change, where divergence of the interlaminar shearing stress is …

Effect Of Thermal Annealing And Carbon Implantation On The Functional Properties Of Nanocomposite Tisin Coatings On Steel, Mohammad Shoeb Ahmed

Theses: Doctorates and Masters

This PhD research contributes to the part of advanced materials technology. The machining industry currently faces tremendous pressures with the need for durable cutting tools suitable for eco-friendly high speed machining operations becoming acute. In this thesis innovative design and synthesis strategies are explored to tailor the properties of nanocomposite coatings. Advanced characterisation techniques are applied to identify the mechanisms that control the mechanical, tribological, and corrosion behaviours of these coatings. Cutting tools protected by these coatings are anticipated to exhibit a unique combination of superior toughness and greater resistance to wear and corrosion, providing significant economic and environmental benefits. …

Structural Health Monitoring Of M1114 High Mobility Multipurpose Wheeled Vehicle Armor System, Frank T. Sha

Theses and Dissertations

The M1114 High Mobility Multipurpose Wheeled Vehicle (HMMWV) has been the workhorse vehicle of the U.S. Armed Forces in Afghanistan and Iraq. Donald Rumsfeld, Secretary of Defense, was faced with massive public criticism in 2004 for not equipping our military personnel in Afghanistan and Iraq with M1114s that had the proper ballistic armor. In May 2004, a $618M Senate Bill was passed to increase the production level of HMMWVs and improve their ballistic protection capabilities while minimizing additional weight. While the military is taking advantage of using composite armor on the HMMWV, it does not have a rigorous method to …

Creep Behavior In Interlaminar Shear Of A Cvi Sic/Sic Composite At Elevated Temperatures In Air And Steam, Matthew T. Pope

Theses and Dissertations

This research investigated the interlaminar shear performance of a SiC/SiC ceramic matrix composite. The interlaminar shear performance was observed in compression of double notched specimens (DNS) at 1200°C in both laboratory air and in steam. Compression to failure tests determined the as-processed interlaminar shear strength and interlaminar shear creep tests were conducted with stresses ranging from -22 MPa to -16 MPa. Primary and secondary creep regimes were observed in all creep tests. The specimens tested in creep at -16 MPa in air achieved run-out, defined as 100 hours at creep stress. The residual strength decreased slightly after 100 h of …

Nondestructive Evaluation Of Aircraft Composites Using Terahertz Time Domain Spectroscopy, Christopher D. Stoik

Theses and Dissertations

Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive …

Analysis Of Multi-Layered Materials Under High Velocity Impact Using Cth, Jason K. Lee

Theses and Dissertations

Multi-layer armor containing ceramic and metallic layers has become more common in the past two decades. Typically, ceramics have high compressive strength which combined with their low density make them highly desirable for armor applications. This research effort numerically simulates high velocity impact of cylindrical projectiles on multi-layer metallic and ceramic targets of finite thickness. The impact of the projectile occurs normal to the surface of the target. The projectiles used are made of either S7 tool steel or tungsten. The targets consist of either rolled homogeneous armor, 4340 steel and boron carbide ceramic or rolled homogeneous armor and boron …

Effects Of Environment On Creep Behavior Of Nextel 720/Alumina-Mullite Ceramic Composite At 1200°C, Christopher L. Genelin

Theses and Dissertations

The creep behavior of an oxide-oxide ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air, in steam and in argon. The composite consisted of a porous alumina-mullite matrix reinforced with laminated, woven mullite/alumina (Nextel/720) fibers. The composite had no fiber coating and relied on its porous alumina/mullite matrix for flaw tolerance. Tensile stress-strain behavior was investigated and the tensile properties were measured at 1200°C in laboratory air. Tensile creep behavior of the CMC was examined for creep stress levels of 73, 91, 114 and 136 MPa. Creep run-out, set to 100 h, was achieved for stress levels ≤ …

Modeling Fracture In Z-Pinned Composite Co-Cured Laminates Using Smeared Properties And Cohesive Elements In Dyna3d, Jason K. Freels

Theses and Dissertations

The purpose of the present research was three-fold: 1) gain a more sophisticated understanding of the response of co-cured composite joints with and without through-thickness reinforcement (TTR), 2) compare the behavior of specimens reinforced with various sizes and densities of reinforcement, and 3) use experimental data to verify the existing DYNA3D smeared property model. Double cantilever beam, end-notch flexure and T-section specimens reinforced with 0.011" diameter z-pins at 2% and 4% volume densities were tested to determine the mode I, mode II and mixed mode (I and II) behavior. Results were added to preliminary research in which tests were conducted …

Characterization Of Functionally Graded Materials, Benjamin D. Chapman

Theses and Dissertations

The purpose of this study was to characterize the behavior of a functionally graded material through experimentation and analytical modeling. Functionally graded materials are a ceramic metal composite which transitions from metal on one face to ceramic on the opposite face. Creating reliable models required verifying the material properties. This was accomplished through the use of a static modulus of elasticity test as well as a dynamic ping test. The natural frequencies from the dynamic test were compared with finite element models to determine which material properties most accurately represented the functionally graded material. It was found that the material …

Creep-Rupture And Fatigue Behaviors Of Notched Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature, Mark A. Sullivan

Theses and Dissertations

Oxide/oxide composites are being considered for use in high temperature aerospace applications where their inherent resistance to oxidation provides for better long life properties at high temperature than most other ceramic matrix composites (CMCs). One promising oxide/oxide CMC is Nextel 720/A (N720/A) which uses an 8-harness satin weave (8HSW) of Nextel 720 fibers embedded in a porous alumina matrix. Possible aerospace applications for N720/A will likely require inserting holes into the material for mounting and cooling purposes. The notch characteristics must be understood to ensure designs using the material are sufficient for the desired application. This research effort examined the …

Experimentation And Analysis Of Composite Scarf Joint, Benjamin M. Cook

Theses and Dissertations

Composite bonded scarf repairs were examined by experimentally measuring and analytically predicting the residual curing strains and strains due to mechanical loading. To accomplish this a three prong approach was used: a full strain field through a repaired laminate's thickness was measured for both a loaded specimen and a specimen with the residual strain released, models were developed for comparison to both states, and data was collected for large tensile test specimens at various stages of being scarf repaired. A ~14:1 straight scarfed one-inch wide specimen was used to collect Moire interferometry data to calculate a full strain field due …

Creep Behavior Of An Oxide/Oxide Composite With Monazite Coating At Elevated Temperatures, Sean S. Musil

Theses and Dissertations

This study focuses on experimental investigation of stress-rupture behavior (creep response) of an oxide/oxide composite in a cross-ply (0/90) lay-up at elevated temperature. The test material, Nextel 610/monazite/alumina composite, employs monazite, an oxidation-resistant interfacial coating designed to improve performance at elevated temperatures. The experimental program included monotonic tensile tests to failure and creep-rupture tests at elevated temperatures. Tensile tests served to establish an ultimate tensile strength (UTS) for the material. The ensuing creep-rupture tests involved stress levels at varying percentages of the UTS. Stress-rupture curves at 900 and 1100 degrees C were established. A family of creep curves for various …

Mechanics Of A Functionally-Graded Titanium Matrix Composite, G. Brandt Miller

Theses and Dissertations

Functionally-graded Titanium Matrix Composites, (F/G TMCs) combine the ideal properties of titanium matrix composites with the more practical machining qualities of monolithic (unreinforced) alloy. This material shows great promise in application to aerospace structural components - even in parts whose design requirements have defied the use of composite materials in the past. Successful implementation of such a material would lead to enhanced aircraft performance. However, the basic properties of a functionally-graded titanium matrix composite need to be investigated. The composite/alloy transition region, or joint area, may be less strong than its constituents and therefore determine the overall performance of the …

Investigation Into The Behavior Of Geometrically Nonlinear Composite Arches, John C. Bailey

Theses and Dissertations

This research modifies the existing finite element formulation of a potential energy based large deformation and moderate rotation theory. Hermitian shape functions replace the existing linear bending angle interpolations. Negligible differences between the two formulations indicate the underlying kinematics limit the accuracy, not the finite element interpolations. Using the new program, numerous nonlinear arch geometries are modeled to investigate the effects of arc length and thickness variations. Local and global snapping phenomena are captured as well as through the thickness shear driven nonlinearities.

An Experimental And Analytical Investigation Of The Iosipescu Shear Test For Composite Materials, Barry Stuart Spigel

Mechanical & Aerospace Engineering Theses & Dissertations

Mechanical properties of composite materials under shear loading are difficult to determine. The Iosipescu Shear test, originally proposed for metals, has in recent years been applied to composites. It has the advantages of small specimen size, simple loading and a reasonably uniform shear stress in the test section.

The purpose of this work is to study the validity of the Iosipescu test method for measuring the shear modulus and shear strength of composites. Finite element analyses indicate that optimum specimen geometry and load locations depend upon the degree of orthotropy of the composite. Test results for a quasi-isotropic graphite/epoxy laminate …

Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel

Theses and Dissertations

This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …

An Experimental And Analytical Investigation Of The Iosipescu Shear Test For Composite Materials, Barry Stuart Spigel

Mechanical & Aerospace Engineering Theses & Dissertations

Mechanical properties of composite materials under shear loading are difficult to determine. The Iosipescu Shear test, originally proposed for metals, has in recent years been applied to composites. It has the advantages of small specimen size, simple loading and a reasonably uniform shear stress in the test section.

The purpose of this work is to study the validity of the Iosipescu test method for measuring the shear modulus and shear strength of composites. Finite element analyses indicate that optimum specimen geometry and load locations depend upon the degree of orthotropy of the composite. Test results for a quasi-isotropic graphite/epoxy laminate …

Curing And Flow Of Thermosetting Resins For Composite Materials Pultrusion, Howard L. Price Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Fibrous composite materials for mechanical and structural applications often are expensive due to high labor costs. One economical way of making composites is pultrusion, a manufacturing process in which resin-impregnated fibers are pulled at a constant speed through a heated die which shapes the resin-fiber mass and cures the resin. Most of the work which has been done on the process has been of an empirical nature, with limited understanding of the process principles. Most of the experience with pultrusion has been gained with polyester resins and glass fibers. Very little experience has been gained with higher performance, more costly …

Analysis Of Moisture Absorption And Diffusion In Fiber Reinforced Polymeric Resin-Matrix Composite Materials, Stephen Stern Tompkins

Mechanical & Aerospace Engineering Theses & Dissertations

The diffusion of moisture through fiber reinforced polymeric-matrix composite materials has been studied analytically. The diffusion in the orthotropic, nonhomogeneous material was modeled, in detail, with a two-dimensional transient diffusion analysis. An effective diffusivity for the composite was determined in terms of the fiber volume fraction and the resin diffusivity. This effective diffusivity is in better agreement with recent data than those previously determined using less complex models.

The influence of both material and environmental parameters on the moisture content of the composite was determined analytically. Predicted moisture contents were compared over a wide range of values for emittance, solar …