THE DETECTION AND MEASUREMENT OF IMPACT DAMAGE IN THICK CARBON-FIBER-REINFORCED LAMINATES BY TRANSIENT THERMOGRAPHY

Transient thermography (TT) images of impact damaged 3.44, 8.66 and 13 .76 mm thick composites, from the impact face and rear face, are compa red with the corresponding ultrasonic c-scan (UCS) images. Comparisons of apparent delamination area and size were made using novel image an alysis techniques. The defect image sizes were also compared with crac k lengths obtained from a selected number of specimens that were secti oned. For all composite thicknesses, the UCS damage area was proportio nal to the impact energy. The damage area obtained by TT from the fron t faces of the specimens did not correlate to the UCS damage areas alt hough there was a correlation for the rear face damage on 3.44 and 6.8 8 mm thick specimens. Crack lengths obtained from sectioning showed th at UCS damage length was equal to the maximum crack length and back an d front sub surface cracks corresponded to back and front TT images. ( C) 1998 Elsevier Science Ltd. All rights reserved.