REFLECTION AND TRANSMISSION OF ACOUSTIC PLANE-WAVES ON AN IMMERSED ORTHOTROPIC AND VISCOELASTIC SOLID LAYER

This paper presents a method of characterizing orthotropic and viscoelastic behavior of some composite materials. The purpose is to measure the nine coefficients of the complex stiffness matrix, by using ultrasonic waves transmitted through a plate-shaped sample immersed in water. From a study of propagation in principal planes that has been reported in a previous publication [B. Hosten et al., J. Acoust. Soc. Am. 82, 1763-1770 (1987)], this paper emphasizes heterogeneous mode conversion and propagation through a nonprincipal plane, inside the composite. A numerical method is proposed for computing reflection and transmission coefficients of plane waves for any incidence plane through an orthotropic, lossy solid layer. Numerical calculations of reflection and transmission are compared to experimental data: Amplitudes, wave vectors, and damping vectors are given for a unidirectional graphite/epoxy composite.