Effects of variable amplitude fatigue on delamination and crack growth rate models

Abstract

Load history effects in fatigue-driven delamination in fibre-reinforced polymer composites are neglected in state-of-the-art non-interaction models although this assumption highly underestimates the delamination growth under variable amplitude (VA) loading. A new phenomenon called “transient delamination growth” has been observed in recent VA fatigue experiments by the authors. This phenomenon is a transient phase with a significantly increased crack growth rate that follows load amplitude changes in VA load spectra. In this presentation the transient delamination growth is characterised from block loading experiments and the phenomenological behaviours are integrated in a new crack growth rate (CGR) model for prediction of delamination under multi-level block loading