Fatigue life simulation of multi-axial CFRP laminates considering material non-linearity

The objective of an on-going DFG research project is to investigate the effect of non-linear stress–strain curves (e.g. τ12–γ12) on the fatigue life simulation of carbon fiber reinforced polymer (CFRP) laminates under variable amplitude cyclic loading. Based on the critical element concept of Reifsnider and Stinchcomb appropriate models including a secant modulus iteration for the non-linear stress analysis, the evaluation of inter-fiber fracture effects applying a fracture plane criterion, and appropriate continuum mechanics based stiffness degradation algorithms to treat both inter-fiber cracking and ply delamination were implemented into an existing fatigue life prediction software. Using this software the fatigue life of a quasi-isotropic vinylester/urethane/carbon fiber composite laminate subjected to miniTWIST variable amplitude loading was analyzed and compared to experimental data.