Characterization of fatigue delamination growth under mode I and II: Effects of load ratio and load history

The study of fatigue delamination growth in composite materials aims to develop a slow-growth approach for composite materials that would provide conservative and reliable results. The present work focuses on the study of the load ratio effect on fatigue crack growth at constant amplitude and on the effect of variable amplitude loading on crack propagation. With this in mind, a Crack Driving Force (CDF) is chosen to attempt to overlap delamination growth curves obtained from different load ratio values for mode I and mode II. It is shown that the CDF collects the effect of the load ratio on the crack growth curves and allows to build a crack growth master curve for mode I and II. Variable amplitude loads are then considered for delamination propagation in mode I. However, variable amplitude loads bring to light a load history effect during fatigue crack growth that the CDF does not take into account.