Experimental investigation of fatigue after impact damage growth in CFRP
D. Biagini (TU Delft - Group Pascoe)
John- Alan Pascoe (TU Delft - Group Pascoe)
René C. Alderliesten (TU Delft - Group Alderliesten)
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Abstract
Damage propagation in fatigue after impact of CFRP is usually monitored by measuring the external area or simply the one-dimensional width of impact delamination using ultrasound inspection. The present work provides experimental evidence demonstrating that this procedure does not account for all the possible damage propagation taking place in CAI fatigue. In the present work, impact and compression after impact fatigue tests were conducted on CFRP laminates. The impact damage, inspected using through-thickness attenuation ultrasound scan, showed the presence of a non-delaminated cone caused by the out of plane compression during impact. In the following fatigue test, first delamination grew internally inside the non-delaminated cone and, only after, outwards, towards the sides of the specimen. In addition to that, the process of stiffness degradation started before any observable damage growth. This provides experimental confirmation to the necessity to reconsider the current definition of fatigue growth in compression fatigue after impact.
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