Numerical assessment of composite laminate repeated load durability following low velocity impact for enhanced aircraft sustainment

摘要

Advanced experimentation techniques such as enhanced XmCT and pulse-echo ultrasonics were used to observe in detail damage mechanisms arising from a low velocity impact to a 32 ply carbon-fibcr-reinforced-plastic (CFRP) composite laminate. Extensive fibre and matrix damage mechanisms and a small impact and back face indentation were observed. The damage and indentation was digitally mapped for input into high fidelity finite element models using the Rx-FEM framework and delamination mapping for CB~2ATA framework to predict the compressive strength after impact (CAI) and the post-impact fatigue durability. Advanced experimental methods such as Thermoclastic Stress Analyses (ISA) and XmCT were used to monitor damage growth and observe in detail the evolved damage morphology. It was found that although the progression to failure was consistent for all specimens, there was quite a large scatter in the measured fatigue life following an 8 J impact and constant amplitude fatigue loading at 80% of the measured static strength. The shortest fatigue life measured was less than 10K. and the longest fatigue life was 115K with most specimens failing between 30K. and 60K cycles. The precise reasons for the scatter is the subject of an ongoing investigation.