Failure modes characterization of impacted carbon fibre reinforced plastics laminates under compression loading using acoustic emission

Composite laminates have low resistance under dynamic loading, particularly impact loading. A low-velocity impact on laminated composites causes various types of damage, such as delamination, fibre breakage, matrix cracking and fibre matrix interfacial debonding. Post-impact compressive strength is one of the greatest weaknesses in carbon fibre reinforced plastics laminates. After impact, due to the delaminations present in the laminates, local instability is triggered, which ultimately reduces considerably their residual strength. In this work, symmetric cross ply carbon fibre reinforced plastics laminates [(0 degrees/90 degrees)(2)](12) were subjected to falling weight impact at two different velocities, 2.5 and 3.5m/s. Compression after impact studies showed substantial differences in failure mode between the two cases, passing from end crushing to crack propagation with higher impact energy. Acoustic emission technique was able to confirm this result and characterize the different types of failure modes during compression after impact test, in particular by frequency distribution.