Study of First Ply Failure in CFRP by Non-destructive Evaluation

Abstract

Carbon fibre reinforced plastic (CFRP) is used in an increasing number of aerospace structures and the integrity of the structures under load must be ensured. It is therefore necessary to be able to detect any possibility of premature failure during testing. First ply failures in uniaxially loaded CFRP specimens have been detected using the acoustic emission technique and identified by the use of amplitude analysis of the emissions. In this way it has been possible to define a criterion for first ply failure which has been applied to difference CFRP matrix systems with several fibre layups and to the off-axis loading situation. A comparison has been made between the predicted behaviour and the experimental results. Analyses based on the Tsai—Hill criterion cannot take into account stacking sequences and this can lead to important differences in behaviour. The criterion which is proposed takes into account the effect of stacking sequence.