Vibro-acoustic Modulation Based Measurements in CFRP Laminates for Damage Detection in Open-Hole Structures

The occurrence of matrix cracks, fibre failures and delaminations results in a critical degradation of the structural integrity of composites. A reliable early detection of these damages is mandatory for a safe operation. In this paper, the application of Vibro-Acoustic Modulation measurement in notched carbon fibre reinforced polymers (CFRP) for damage detection is demonstrated. A piezoceramic actuator introduces an ultrasonic signal into the specimen, which is modulated by a low-frequency vibration excited by a servo-hydraulic testing system. The specimens tested are open hole tensile specimens according to ASTM D5766, made from a quasi-isotropic CFRP layup. Degradation in the form of matrix cracks or delaminations localised along the drill hole significantly reduces the stiffness and can be detected as a modulation increase. Taking into account the extent of the crack size and the acoustic emission (AE), a magnitude estimate of the modulation increase is possible. In consequence, the presented method can be used for damage monitoring in CFRP.