Acoustic Emission Monitoring of Compression-After-Impact Test of CFRP Laminates Damaged by Simulated Lightning Strikes

초록

Impact-damaged laminates of carbon-fiber reinforced plastics (CFRP) were tested under compression-after-impact (CAI) mode and the progress of further damage due to compressive loading has been monitored by acoustic emission (AE). The impact damage was induced not mechanical loading but by a simulated lightning strike. The CFRP laminates were made of CFRP prepregs prepared by coating of conductive nano-particles directly on the fibers and the coupons were subjected to the simulated lightning strikes with a high voltage/current impulse of 10~40kA within a few microseconds. The effects of nano-particles coating and the degree of damage induced by the simulated lightning strikes on the AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the initiation of AE activity with the compressive loading. The degree of damage was also measured in terms of damage area by using ultrasonic C-scan images after being damaged by the simulated lightning strikes. From the results assessed during the CAI tests of damaged CFRP showed that AE monitoring appeared to be very useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.