Scale dependent effects on the fatigue response of woven textile composites

Abstract

The tensile fatigue response of notched twill textile composites is studied in this investigation. The goal is to evaluate the effect of a notch of fixed size and its placement (with respect to the textile’s mesostructure), on the tensile fatigue response, thereby showing that scale effects are important in understanding and explaining the obtained experimental results. Load-controlled fatigue experiments, supplemented with the Digital Image Correlation (DIC) technique to monitor strains, are conducted. A finite element based fatigue damage model is presented to model matrix degradation and the fatigue response of the twill textile composite. Based on the experimental results, we can distinguish between two types of fatigue response — fatigue resistant (FR) and fatigue susceptible (FS). Because the size of the notch is comparable to the characteristic geometric length scales of the mesostructure, its placement with respect to the mesostructure affects the overall damage evolution and fatigue life across these two families of specimens. The finite element model is shown to reproduce the key features observed in the experiments.