Micro-Scale Numerical Simulation for Residual Strength of CFRP After Cyclic Tensile or Out-of-Plane Shear Loadings Fatigue

In this study, micro-scale numerical simulations were performed to evaluate the residual strength of carbon fiber reinforced plastics (CFRP) subjected to cyclic transverse and out-of-plane shear loading fatigue. The simulations utilized a finite element method incorporating an entropy-based damage criterion for the matrix resin. This method aimed to link entropy generation to strength degradation, with the parameter α_o (s)determined as a function of entropy. Cyclic tensile and shear analyses were conducted to correlate residual strength with entropy accumulation, establishing a linear relationship for α_o (s). The results demonstrated meso-scale strength degradation based on micro-scale numerical simulations. Material constants for the epoxy resin matrix were determined through creep and tensile tests, and a generalized Maxwell model with 15 elements was used to represent the viscoelastic behavior. Numerical simulations employed the Abaqus/Standard 2020 software, with the epoxy resin matrix behavior implemented via a UMAT subroutine. The analysis revealed a linear relationship between entropy and residual strength for both cyclic tensile and out-of-plane shear loading. This approach enhances experimental insights with numerical predictions, offering a comprehensive understanding of CFRP strength degradation under fatigue loading.