Micromechanical studies of progressive failure of S2 glass/toughened epoxy composites and composite joints.
Item
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Title
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Micromechanical studies of progressive failure of S2 glass/toughened epoxy composites and composite joints.
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Identifier
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AAI3205017
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identifier
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3205017
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Creator
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Cheung, Chin Keung.
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Contributor
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Adviser: Benjamin Liaw
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Date
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2006
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Mechanical
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Abstract
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In this dissertation, micromechanical studies of progressive failure of S2 glass/toughened epoxy composites and composite joints under tensile loading tested from low to elevated temperature are presented. Because of their superiority in light-weight, high specific stiffness, strength and toughness S2 glass/toughened epoxy composites have been used to replace traditional metals and conventional composites with brittle resin in many engineering structures. One of the salient features of the thermomechanical behavior of unidirectional S2-glass fiber/toughened-epoxy matrix composites is that when loaded under uniaxial tension, its dominant failure mode is fiber breakage, instead of the more-frequently observed matrix cracking in most commercial composite materials with untoughened matrix. The main objective of this research is to use micromechanics-based experimental-analytical-numerical approaches to investigate the progressive failure of this advanced composite under uniaxial tensile load at various temperatures.;Two micromechanical approaches were adopted for the study of progressive failure of dog-bone tensile specimens: a Mechanics-of-Materials approach for unidirectional lay-up configuration and a 3-D Elasticity approach for cross-ply, angle-ply and quasi-isotropic lay-up configurations. The dominant failure mode for unidirectional specimens was fiber breakage. Using Strength of Materials and the rule of mixture, stress-strain curves for unidirectional specimens were predicted in good agreement with experimental results. For the cross-ply, angle-ply and quasi-isotropic configurations, the dominant failure modes were transverse matrix cracking and/or shear failure. A 3-D Elasticity approach was adopted to simulate the stress-strain curves and failure progression. The predictions matched the experimental results very well.;For the composite strips with a center hole and pin-joint specimens, several design parameters (e.g., hole/pin size, the distance from the hole center of the pin joint specimen to edge, stacking sequence, temperature, etc.) were varied. Damaged-induced stress-strain curves for [0°], [90°] and [+/-45°) dog-bone specimens under uniaxial tension were first characterized experimentally to document damage evolution along the longitudinal direction (i.e., fiber breakage), perpendicular to the longitudinal direction (i.e., transverse matrix cracking) and shear failure, respectively. A nonlinear elastic orthotropic material model based on these data was then proposed. (Abstract shortened by UMI.).
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
