Ultrasonic inspection of composites materials: Application to detect impact damage

Failures detection in composite laminates is complicated respect to conventional non-destructive testings for metal structures, due to their sensibility to echoes drown in noise depending by the different properties of the constituent materials and the multi-layered composites structures. The latter, in particular, are sensitive to impact damage and also a low-energy impact can results in a severe loss of the load capacity as a result of delamination. In this study, the effectiveness of the detection of the damage in low-velocity impacts in several different composite laminates, at different energy levels, is investigated by using ultrasonic technique. The latter technique was adopted to verify its capability to afford info on the shape and the size of the delamination, also in the presence of entirely different parameters. It was useful even to test the influence of different factors on the dynamic behavior of the studied composites. Pulse-echo method with faced array transducers (f = 5 MHz) was used to diffuse and receive ultrasound waves. The results provided information useful to understand the damage mechanisms and the onset and the propagation of the damage.