Using a residual strength model to predict mode II delamination failure of composite materials under block fatigue loading

An experimental investigation was undertaken to measure delamination growth to the point of failure under spectrum loading including the effects of cycle sequences. Composite coupons were subjected to Mode II fatigue loading using a reversible three point bend test rig under displacement control. Stress-life curves were established using results from a series of constant amplitude fatigue tests. Variable loading effects were then assessed using a series of methodical block loading fatigue tests for which a residual strength method was successfully adjusted for use with displacement controlled test data. The model produced conservative predictions which displayed good agreement with experimental results.