Characterization of composite materials by ultrasonic methods: modelization and application to impact damage

This paper presents some ultrasonic methods to detect and to characterize defects, possibly obtained after damage caused in composite materials. Firstly, a two-dimensional ultrasonic cartography, performed section by section, at different positions from the impact point, allows the participation of the delamination mechanisms which took part through the thickness of a pultruded glass fiber-reinforced plastic composite beam, to be analyzed. A very good agreement has been found with destructive testings. Furthermore, some examples are given on the use of an ultrasonic propagation model which has been developed. This model permits optimum experimental configurations to be determined, by the use of transmission and reflection coefficients or of Lamb waves. In addition, experimental and modelized time signals have been compared. (C) 1998 Elsevier Science Limited. All rights reserved.