Ultrasonic evaluation of matrix damage in impacted composite laminates

Conventional ultrasonic inspection methods are largely used for detection of delaminations in composite materials while only recently new techniques have been proposed to identify matrix cracks in simple tension loaded coupon specimens. In this study delaminations and matrix cracking caused by low-energy impacts on quasi-isotropic carbon/PEEK laminated plates are examined by means of different pulse-echo techniques: conventional time-of-flight and amplitude C-scans at normal incidence an used to check for the presence of delaminations, while backscattering C-scans tin which the transducer is set at an angle to the laminate plane) allow the detection of matrix cracks through the laminate thickness. Selected results from full waveform ultrasonic analysis of impacted carbon/PEEK laminates are discussed and compared with X-ray data in order to demonstrate the efficiency of the proposed inspection technique.