A study of obliquely propagating longitudinal shear waves in a periodic laminate

The basic purpose of this work is to demonstrate, by quite simple and explicit calculation, the possibility that a simple laminate composed of ordinary materials can display the kind of response associated with a "metamaterial". Specifically, a wave of Floquet--Bloch type is analyzed, taking careful account of the requirements of causality and passivity. Then, the generation of such a wave by transmission, from ordinary homogeneous material, into a half-space composed of the laminate is considered. As is well-known for any dispersive material, phase velocity is distinct from group velocity, and information is carried by the latter. Thus, in line with the discussion of photonic crystals by Notomi [1], refraction is considered in terms of the group velocity. Negative refraction appears never to occur, if the interface between ordinary material and composite is parallel to the interfaces in the composite but negative refraction is possible, over an appreciable frequency range, if the interface between ordinary material and composite is orthogonal to the interface in the composite.

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