Elastic wave propagation in honeycomb structures

Abstract

An investigation into elastic stress wave propagation through three types of honeycomb structures - two made of aluminum with different cell sizes, and one constructed from reinforced phenolic resin fiberglass - is undertaken. They are subjected to lateral elastic compression, both quasi-statically and via impact. Loading is applied in the two (orthogonal) directions of symmetry to determine the respective apparent overall elastic modulus and apparent wave speed. As symmetry in these two directions differs, the structure is anisotropic and the results show that the mechanical and wave propagation characteristics are governed by several parameters, such as the cell size, cell wall length ratio, angle between cell walls, cell wall thickness and cell wall material. Estimates of the apparent wave speed in both directions, based on continuum analysis, are compared with experimental results. This reveals that such an approach is untenable. Analysis of elastic stress transmission along the solid cell walls of the structure shows that wave propagation is governed by two modes of load transmission - longitudinal and flexural waves - depending on the orientation of the cell walls to the direction of the applied load.