Ultrasonic NDE techniques for the evaluation of matrix cracking in composite laminates

Abstract

Experimental methods for detecting matrix cracking in composites specimens are often costly and time consuming. In an effort to maximize the information obtained from experimental tests and to establish a correlation between the experimental and nondestructive evaluation (NDE) techniques, a series of investigations have been undertaken. To evaluate the progression of matrix cracks in BMI composite laminates, three NDE techniques were selected and compared as to their relevance and accuracy: acoustic emission, ultrasonic C-scans, and ultrasonic polar backscattering methods. While traditional C-scans are sensitive to delaminations 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 the results obtained from acoustic emission techniques and through optical microscopy.