Damage-property analysis of carbon fiber-reinforced plastic based on homogenization theory

In this study, the damage-development behavior of carbon fiber-reinforced plastic (CFRP) laminates considering the nonlinear mechanical properties of a matrix resin was investigated through a numerical simulation based on a homogenization theory and continuum damage mechanics. A scalar damage variable was applied to elasto-viscoplastic constitutive equations, following which, the constitutive equations were introduced into the homogenization theory for elasto-viscoplastic materials. Uniaxial tensile tests including unloading and reloading phases under several strain rates were performed using a specimen made of an epoxy resin. The damage-development behavior of the unidirectional CFRP laminates was then analyzed using the homogenization theory. From the numerical results, viscoplastic behavior was observed in the stress–strain curves, and the stress decreased drastically as the damage of the epoxy resin developed. The microscopic distributions showed that the failure initiated at the epoxy resin around the fibers arranged along the loading direction and progressed by connecting the high damage variable regions of the epoxy resin. Uniaxial tensile tests of the unidirectional CFRP laminates were also performed to validate the numerical results. The experimental fracture stresses were distributed between the maximum and minimum stresses at the failure starting points obtained from the numerical results. Thus, it was confirmed that the proposed numerical method could analyze the damage-development behavior of CFRP laminates.