ABSTRACT
Normal stresses appear as a consequence of finite deformations under simple shearing. Following the discussion by Ferry (1980) and based on a simple
1 INTRODUCTION
1.1 Background
Understanding and modeling the mechanical response of polymers and polymer-based composites is of great interest for defense and commercial applications related to the need for predictive constitutive model descriptions for use in largescale finite-element simulations of damage and deformation. Cellular solids are a type of polymer composites where a large fraction of the material is in the form of voids. The relative density (ρr/ρs) is an important feature of cellular solids, ρr is the density of the cellular material, ρs, the density of the solid matrix. In general if the relative density is above 0.3, the material can be regarded as a solid containing more isolated pores (voids) rather than a cellular structure (honeycomb). Since this foam like materials are used for applications which require mechanical strength, a fundamental understanding of the mechanical behavior of foams is indispensable. Therefore, the properties of foams must be measured under different loading and dynamic conditions to develop theories that describe and explain their behavior. Due to the fact that foams are often used under compression and an additional shear stress is imposed by motions of the system, combined loads should be studied and the foam behavior should be predicted accordingly.
