Effect of physical non-linearity on cyclic fatigue life prediction of polymer matrix composites

Abstract

The objective of an on-going research project is to investigate the influence of physical non-linearity on the cyclic fatigue life prediction of polymer matrix composites. The experimental investigation of the material non-linearity, the subsequent derivation of mathematical models to describe this behavior and the increased computing effort for the calculation of fatigue life based on non-linear material models mean an additional work load. To assess the impact of non-linear material models on the cyclic fatigue life prediction of polymer matrix composites a parameter study on the influence of experimentally determined non-linear stress-strain relationships on the fatigue life calculation using computer experiments was carried out. A software to predict the fatigue life of composites was extended to include nonlinear stress analysis, inter-fiber failure effects and stiffness degradation based on the fracture plane concept of Puck. From parameter variations and parameter combinations to assess the influence of the intensity of the material nonlinearity of the in-plane stress-strain relationships it was found that material non-linearity effects the fatigue life prediction. Therefore, non-linear stress-strain relationships should be included in fatigue life prediction algorithms allowing a more realistic determination of the behavior of fiber reinforced polymer matrix composites under cyclic fatigue loading. ©Freund Publishing House Ltd.