Abstract

In this talk we discuss how nonlinear pre-stress affects the manner by which elastic waves propagate in complex materials. We begin with an overview of how pre-stress changes propagation in simple homogeneous elastic media. The key point here is that it induces anisotropy in the material, but it can also induce a (perhaps unexpected) modification to the symmetry properties of the incremental elastic modulus tensor. This property is then exploited to explain how pre-stress than be employed as a natural cloaking mechanism around a region of space for specific types of nonlinear materials. We then go on to take this property further in complex materials with periodic arrays of coated scatterers. We show that materials can be designed such that the band-gap structure is invariant, or at least close-to-invariant to imposed deformation for both in-plane and antiplane waves propagating in the pre-stress structure. We finish by discussing pre-stressed foams, including some recent experimental results on the buckled microstructure of syntactic foams under large pre-stress.