Development of nonlinear constitutive laws for anisotropic and asymmetric fiber reinforced composites

A plane-stress constitutive law was developed to describe the inelastic nonlinear, anisotropic, and asymmetric mechanical behavior of fiber reinforced composites under the elasto-plasticity framework, in particular, based on the kinematic hardening model. A yield criterion that describes anisotropic and asymmetric yield behavior was proposed, while the anisotropic translation of the yield surface was assumed to account for the directional difference of hardening behavior. The proposed constitutive equation was then implemented into the commercial FE program ABAQUS with the aid of the user material subroutine. Experimental procedures to characterize the material parameters of the proposed constitutive equation were presented for 313 braided glass/Kevlar fiber reinforced composites. Verification performed for three point bending tests showed good agreements.