Air-coupled ultrasonic C-scan technique in impact response testing of carbon fibre and hybrid: glass, carbon and Kevlar/epoxy composites

The ultrasonic air-coupled C-scan technique and X-ray radiography were used to detect impact damage in thin carbon fibre/epoxy composite plates. The sizes of damage zones were found in good agreement for both techniques employed. The presence of a polymer film on the sample surface has been shown to be useful in detecting the impact damage. Air-coupled C-scan technique was selected for defect size estimation in further studies of impact and post-impact response of hybrid laminates for naval structures. Reinforcements of carbon and glass, woven Kevlar/carbon and Kevlar/glass fabrics have been studied. Minor differences in post-impact compression performance of laminates, in which carbon fibres have been partly replaced by glass fibres, may indicate that regarding the impact behaviour, carbon fibre laminates can be safely replaced by cheaper carbon/glass or Kevlar glass laminates and woven Kevlar/carbon laminates by Kevlar/glass ones.