Damage initiation, progression and failure of polymer matrix composites due to manufacturing induced defects

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Title: Damage initiation, progression and failure of polymer matrix composites due to manufacturing induced defects
Author: Chowdhury, Khairul Alam
Abstract: In polymer matrix composites (PMCs ) manufacturing processes can induce de - fects , e .g . , voids , fiber misalignment , irregular fiber distribution in the cross -section and broken fibers . The effects of such defects can be beneficial or deleterious de - pending on whether they cause failure suppression or enhancement by localized de - formation processes e .g . , crazing , shear yielding and fiber -matrix debonding . In this study , a computational approach is formulated and implemented to develop solu - tions for general boundary -value problems for PMC microstructures that accounts for micromechanics -based constitutive relations including fine scale mechanisms of material failure . The defects considered are voids , and the microstructure is explic - itly represented by a distribution of fibers and voids embedded in a polymer matrix . Fiber is modeled as a linearly elastic material while the polymer matrix is mod - eled as an elastic -viscoplastic material . Two distinct models for the matrix behavior are implemented : (i ) Drucker ? ? ? ? ? ?Prager type Bodner model that accounts for rate and pressure -sensitivity , and (ii ) improved macromolecular constitutive model that also accounts for temperature dependence , small -strain softening and large -strain harden - ing . Damage is simulated by the Gearing -Anand craze model as a reference model and by a new micromechanical craze model , developed to account for craze initiation , growth and breakdown . Critical dilatational energy density criterion is utilized to predict fiber -matrix debonding through cavitation induced matrix cracking . An extensive parametric study is conducted in which the roles of void shape , size and distribution relative to fiber in determining damage initiation and evolution are investigated under imposed temperature and strain rate conditions . Results show there are significant effects of voids on microstructural damage as well as on the overall deformational and failure response of composites .
URI: http : / /hdl .handle .net /1969 .1 /5787
Date: 2007-09-17

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Damage initiation, progression and failure of polymer matrix composites due to manufacturing induced defects. Available electronically from http : / /hdl .handle .net /1969 .1 /5787 .

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