Numerical modelling of fatigue degradation of fibre-reinforced composite materials

Fatigue of fibre-reinforced composite materials is a quite complex phenomenon, and the fatigue behaviour of these heterogeneous materials is fundamentally different from the behaviour exposed by metals. Due to the degradation of the stiffness properties during fatigue life, stresses are continuously redistributed across the composite construction, which is clearly not the case for metals. This paper presents a new finite element approach to model the fatigue behaviour of fibre-reinforced composite materials as well as the continuous stress redistribution due to the stiffness degradation. First the bending fatigue setup and the experimental results are discussed. Next a local damage model for stiffness degradation is proposed. This model has been implemented in both a numerical software package (Mathcad(TM) and a commercial finite element code (SAMCEF(TM)). The latter implementation proves to be a powerful tool to model the fatigue damage of composites and to predict the residual stiffness of the composite construction as a whole.