ULTRASONIC NDE TECHNIQUES FOR THE EVALUATION OF MATRIX CRACKING IN COMPOSITE LAMINATES

Experimental methods for detecting matrix cracking in composites speci mens are often costly and time consuming. fn an effort to maximize the information obtained from experimental tests and to establish a corre lation between the experimental and non-destructive evaluation (NDE) t echniques, a series of investigations have been undertaken. To evaluat e the progression of matrix cracks in BMI composite laminates, three N DE techniques were selected and compared as to their relevance and acc uracy: acoustic emission, ultrasonic C-scans, and ultrasonic polar bac kscattering methods. While traditional C-scans are sensitive to delami nations but not to matrix cracks in the specimen, polar backscattering scans are evaluated for the detection of crack initiation, location, evolution, as well as crack density. These results are compared with t he results obtained from acoustic emission techniques and through opti cal microscopy.