VISUALIZATION OF ULTRASONIC WAVE IN CFRP WITH ACOUSTIC ANISOTROPY USING LASER SCANNING AND ESTIMATION OF ELASTIC CONSTANTS

Abstract

Carbon fiber reinforced plastic (CFRP) is made of stacks of plies, each of which is reinforced by carbon fibers. Since the anisotropy due to the fiber orientation and lay-up of plies shows directional dependency of wave velocity, it is important to know the acoustic property in CFRP in advance of ultrasonic testing. The elastic stiffness constants are fundamental input parameters for simulation of ultrasonic wave propagation in CFRP. In this paper, the elastic constants are determined using wavefield data of ultrasonic propagation on surfaces of CFRP. First the ultrasonic wave propagation is experimentally visualized by a non-contact ultrasonic generation method using scanning laser source. Then phase velocities are extracted from the wavefield data processed by the time-space Fourier transform. By optimizing the elastic constants in the Christoffel equation using the measured phase velocities, five independent components of the elastic constants in the unidirectional CFRP are determined. The accuracy of the estimated elastic constants is validated by a static compression test. Furthermore, the group velocities calculated in the finite element analysis using the estimated elastic constants are compared with the measured ones in the experiment.