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Full-Text Articles in Engineering
Elasticity Of Planar Fiber Networks, Xiangfa Wu, Yuris A. Dzenis
Elasticity Of Planar Fiber Networks, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
A micromechanics model is proposed for the elasticity of planar fiber networks (FNs). The FN is created by random deposition of linearly elastic straight rods within a region. The rods are bonded rigidly at contacts. Under external in-plane loading, the FN deformation consists of fiber bending, elongation, and contraction. An effective constitutive relation for fiber network is developed by averaging the strain energy dissipated by all possible fiber deformations in all directions. Numerical calculations are performed to analyze the effects of fiber aspect ratio and fiber concentration on the effective stiffness of the planar random FN. Finite element analysis (FEA) …
Damage-Induced Modeling Of Asphalt Mixtures Through Computational Micromechanics And Cohesive Zone Fracture, Yong-Rak Kim, D. H. Allen, D. N. Little
Damage-Induced Modeling Of Asphalt Mixtures Through Computational Micromechanics And Cohesive Zone Fracture, Yong-Rak Kim, D. H. Allen, D. N. Little
Department of Engineering Mechanics: Faculty Publications
This paper presents a computational micromechanics modeling approach to predict damage-induced mechanical response of asphalt mixtures. Heterogeneous geometric characteristics and inelastic mechanical behavior were taken into account by introducing finite element modeling techniques and a viscoelastic material model. The modeling also includes interface fracture to represent crack growth and damage evolution. The interface fracture is modeled by using a micromechanical nonlinear viscoelastic cohesive-zone constitutive relation. Fundamental material properties and fracture characteristics were measured from simple laboratory tests and then incorporated into the model to predict rate-dependent viscoelastic damage behavior of the asphalt mixture. Simulation results demonstrate that each model parameter …
Antiplane Surface Acoustic Waves Propagating In Elastic Half-Space Coated With An Anisotropic Laminate, Xiangfa Wu, Yuris A. Dzenis
Antiplane Surface Acoustic Waves Propagating In Elastic Half-Space Coated With An Anisotropic Laminate, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
Dispersion relation of antiplane surface acoustic waves (SAWs) propagating in elastic half-space coated with an anisotropic laminate was determined explicitly by means of Stroh's formalism within the subsonic range, where is no energy leakage into the substrate. During the procedure, the governing dynamic equation in each anisotropic layer and the displacement–traction continuity at interfaces were exactly satisfied by Stroh's functions. Explicit algebraic equation was derived for determining the dispersion relation. As an example, the wave number vs. phase velocity diagram for steel half-space coated with a graphite-fiber/epoxy laminate with a [± 45°/0°2] lay-up was demonstrated. The given method …
Electrohydrodynamic Instability Of Thin Conductive Liquid Films, Xiangfa Wu, Yuris A. Dzenis
Electrohydrodynamic Instability Of Thin Conductive Liquid Films, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
This paper considers the effect of surface charges on the surface instability of thin conductive liquid films. A characteristic relation is obtained for determining the wave number of the fastest growing mode as a function of surface tension, dispersive van der Waals force, and electrostatic tractions exerted by the film surface charges. Two natural length scales of the microsystem are further introduced to account for the coupling effects on the dewetting pattern development. The present results can be used for controlled surface pattern modulation in a spinodal-dewetting scenario via amplification of surface waves of selected modes.
Experimental Determination Of Probabilistic Edge-Delamination Strength Of A Graphite–Fiber/Epoxy Composite, Xiangfa Wu, Yuris A. Dzenis
Experimental Determination Of Probabilistic Edge-Delamination Strength Of A Graphite–Fiber/Epoxy Composite, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
Probabilistic edge-delamination strength of a thermosetting polymer composite was studied experimentally in this work. During the procedure, by means of edge-delamination tensile test, the graphite–fiber/epoxy laminate made of unidirectional Toray P7051S- 20Q-1000 prepregs with an optimized lay-up of [122/–122/02]S was used for examining its probabilistic distributions of the edgedelamination onset stress and the ultimate tensile strength. Acoustic emission (AE) equipment and optical microscope were utilized to capture the edge-delamination initiation and characterize the failure modes during delaminating. Fractographical analysis based on scanning electron microscope (SEM) was conducted for the characterization of the microscopic …
Determination Of Dynamic Delamination Toughness Of A Graphite-Fiber/Epoxy Composite Using Hopkinson Pressure Bar, Xiangfa Wu, Yuris A. Dzenis
Determination Of Dynamic Delamination Toughness Of A Graphite-Fiber/Epoxy Composite Using Hopkinson Pressure Bar, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
Modified dynamic three-point-bending and compact shearing test configurations based on Hopkinson pressure bar (HPB) and crack detection gage (CDG) (Vishay Intertechnology, Inc) were used for the determination of the dynamic mode I and mode II delamination-initiation toughness of a unidirectional graphite-fiber/epoxy composite made of P7051S-20Q-1000 prepregs (Toray Composites America). The transient loading history was recorded precisely by the HPB installed with a highresolution digital oscilloscope, and the crack initiation and delay time were captured using the CDG. By means of dynamic finite-element analysis (FEA) of the impact processes with the loading history and crack initiation time as input, the critical …
Colossal Dielectric And Electromechanical Responses In Self Assembled Polymeric Nanocomposites, Cheng Huang, Q. M. Zhang, Jiang Yu Li, Manese Rabeony
Colossal Dielectric And Electromechanical Responses In Self Assembled Polymeric Nanocomposites, Cheng Huang, Q. M. Zhang, Jiang Yu Li, Manese Rabeony
Department of Engineering Mechanics: Faculty Publications
An electroactive polymer nanocomposite, in which high dielectric constant copper phthalocyanine oligomer (o-CuPc) nanoparticles are incorporated into the block polyurethane (PU) matrix by the combination of “top down” and “bottom up” approaches, was realized. Such an approach enables the nanocomposite to exhibit colossal dielectric and electromechanical responses with very low volume fraction of the high dielectric constant o-CuPc nanofillers (~3.5%) in the composite. In contrast, a simple blend of o-CuPc and PU composite with much higher o-CuPc content (~16% of o-CuPc) shows much lower dielectric and electromechanical responses.
A Model For Predicting The Evolution Of Damage In Viscoelastic Particle-Reinforced Composites, G. D. Seidel, D. H. Allen, K. L. E. Helms, S. E. Groves
A Model For Predicting The Evolution Of Damage In Viscoelastic Particle-Reinforced Composites, G. D. Seidel, D. H. Allen, K. L. E. Helms, S. E. Groves
Department of Engineering Mechanics: Faculty Publications
A viscoelastic cohesive zone model is employed within the framework of a finite element code to analyze a two-phase viscoelastic particle-reinforced composite material consisting of a relatively stiff aggregate embedded in a copolymer binder. The composite of interest, LX17, is noted to have a very large aggregate volume fraction and as such, aggregate grain boundaries were generated within finite element meshes along which viscoelastic cohesive zones have been embedded to model the binder. It has been observed experimentally that the majority of damage in LX17 occurs within the binder, and thus, a damage evolution law has been applied to the …