MINI-CONSTITUTIVE FINITE-ELEMENT MODEL FOR PLASTIC RESPONSE OF UNIDIRECTIONAL FIBER COMPOSITES

A micromechanical finite element model to compute the overall instanta neous stiffness of fiber-reinforced composites in elastoplastic respon se is presented. This model is applicable to a periodic diamond array of elastic circular fibers embedded in an elastic-plastic matrix subje cted to a plane stress loading. This model enforces symmetry and anti- symmetry conditions isolating the smallest unit cell and should greatl y increase the speed of doing ''built-in'' micromechanics within a lar ger finite element program, because of the small number of degrees of freedom (12-14 DOF). At this stage of development, effective propertie s of a composite with a nearly incompressible matrix are presented to assess the model's plasticity performance. Comparison with a fine grid finite element solution shows very good results and demonstrates the effectiveness of the mini-model presented.