An homogenization procedure for the description of pre‐ and post‐yielding stages of isotropic polymer composites

Abstract There will be integrated and provided a complete set of relations for an exact description of the whole mechanical behavior of a composite, i.e. from low to high deformations and stresses. The results from an extended homogenization procedure will be presented here, starting from the fact that the basic material—polymer matrix—presents viscoelastic and viscoplastic response. Analyzing the results from a unidirectional compression loading of an isotropic polymer composite, we found a characteristic enhancement of yield stress and also a distinct hardening stage: Features that generally are absent from similar test sets of unidirectional tension loading. The need for a more systematic study of this loading case in order to explain and describe correctly this inversion/asymmetry in relation to tension reference case, led us to the identification of a yielding stress impetus quantity: k = τ/( s + a · p ), a critical stressed area, and to a true strain rate of loading matrix and reinforcement. We found that only by knowing the interaction between them and the entire equations set that controls the corresponding quantities, we will be able to describe correctly the real behavior of composites, i.e. their viscoelastic, viscoplastic, strain softening, and strain hardening response. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers