Effect of strain rate on nonlinear deformation behavior in CFRP composites

Abstract

This paper presents the effect of strain rates on nonlinear deformation behavior of CFRP composites. An elastic-plastic constitutive model is developed on the basis of both a complementary elastic energy function and a plastic potential, assuming that linear elastic deformation occurs in the fiber direction and that nonlinear strain in the shear direction is decomposed into nonlinear elastic strain and plastic strain. A one-parameter and a two-parameter plastic potential are employed to describe post-yielding behavior of composite laminae. Nonlinear elastic shear strain is measured by means of loading/unloading tensile tests of [±45°]s specimens. Off-axis tensile tests are performed to obtain the universal effective stress-effective plastic strain relation under monotonic loading. It is shown that rate-dependence of effective stress-effective plastic strain relation can be explained by determining anisotropy parameters of the plastic potential as functions of initial effective plastic strain rate.