Anisotropy Effects on Lamb Waves in Composite Plates
There is currently considerable interest in metal matrix composites for applications in space structures. Both particle and fiber reinforced materials are under investigation. Our recent studies [1,2] have shown that these materials can usually be characterized as transversely isotropic having five distinct elastic stiffnesses. Using a wave scattering formalism, models of their rheology were derived for predicting these five elastic stiffnesses. Manufactured parts (plates, tubes, etc.) containing these materials have unique properties, which are subjects of considerable interest for ultrasonic nondestructive evaluations, impact response, and vibrations. In this paper we have studied guided wave propagation in plates of two different materials: SiC particle-reinforced aluminum alloy and graphite fiber-reinforced magnesium. As was shown in previous investigations [1,2], both of these materials show transverse isotropic symmetry. Here it has been assumed that the axis of symmetry lies in the plane of the plate. Thus for propagation in an arbitrary direction parallel to the plate, the motion is three dimensional, i.e., the equations governing the three components of displacement are coupled. This causes considerable complexity in the dispersion equation. Here we have presented solutions to this equation showing different behaviors for the two materials.