CFRP barely visible impact damage inspection based on an ultrasound wave distortion indicator

The impact damage of carbon-fiber-reinforced polymers (CFRPs) must be considered important in order to avoid catastrophic accidents. Low-velocity impact commonly results in barely visible impact damages (BVIDs) in a CFRP component, and is impossible to be detected by visual inspection or machine vision. To rapidly and effectively detect BVIDs in CFRPs, this work proposes a damage inspection method based on an ultrasound wave distortion indicator. The indicator reveals ultrasound higher harmonics, subharmonics, and self-modulation caused by local damage in CFRPs. The experimental system was built after the proposed non-destructive testing (NDT) methodology was introduced. An intact CFRP plate specimen, and specimens with BVIDs and visible impact damage (VID) were tested using the proposed method. The relationship between impact energies and the ultrasound wave distortion indicator was built. The proposed method could provide an effective inspection means for assessing the impact damage of CFRP materials.