Effects of Moisture Content on Nonlinear Deformation Behavior of CF/Epoxy Composites

Abstract

This paper presents the effects of moisture content on nonlinear stress-strain behavior of CFRP composites. First, a plane-stress elastic-plastic constitutive model is newly developed based on a fourth-order complementary elastic energy function and a one-parameter plastic potential in which an anisotropy parameter changes with plastic deformation. Secondly, elastic constants, the anisotropy parameter and the effective stress-effective plastic strain relation are determined at various moisture contents for both the present model and the conventional model where the anisotropy parameter is constant. Finally, the above results are utilized to predict the off-axis stress-strain response. The transverse and shear elastic moduli decrease with increasing moisture content, and the anisotropy parameter and the effective stress-effective plastic strain relation also vary with moisture content. Off-axis stress-strain curves predicted by the present model agree with experimental results better than those predicted by the conventional model.