Influence of anisotropic fiber properties on tensile elastic modulus estimation for carbon fiber reinforced thermoplastics

Abstract

The influence of anisotropic fiber properties on estimation of the elastic modulus of carbon fiber-reinforced polyamide 6 (CFRPA6) was studied using two kinds of micromechanics models; Nairn et al. and Hashin (N–H) models, and Mori–Tanaka (M–T) model. First, these models’ accuracy was verified by comparison with an elastic modulus measured for injection molded dumbbell specimens of CFRPA6. Although there was a slight difference between the elastic moduli estimated from the N–H models and the M–T model, the difference was discussed in terms of model properties. Next, estimation errors caused by assuming carbon fiber (CF) as isotropic were calculated under several conditions. The maximum error occurred in the condition that the tensile direction was perpendicular to the fiber axis. Despite CF had large anisotropy, it was approximately 10% for both models. We infer that the small error was caused by a specific stress field.