Acoustic emission based fatigue failure criterion for CFRP

The aim of the study presented here was to determine whether an acoustic emission (AE) based failure criterion could be designed for determining the failure of an assembled commercial CFRP product during cyclic testing. The failure was defined by a stiffness based criterion. A total of 75 products were cyclic tested and AE measurements made at regular intervals. Presented is an AE based failure criterion equivalent to the stiffness based criterion. This is accomplished for a complex shaped composite under multi-axial loading conditions. The criterion determines a failure when the value of a parameter being monitored exceeds a specified threshold. The parameter used is a function of the number of AE hits in each measurement. Instead of filtering out AE hits from damage growth, the failure criterion is based on AE hits from both cumulative damage and damage growth. The results show that the AE technique can be applied in a realistic setting where AE from cumulative damage greatly outnumber AE related with damage growth.