Mechanics of Elastomer--Shim Laminates

The mechanics of laminates of elastomer and shims of high modulus material are reviewed. Such structures are often built to provide engineering components with specified, and quite different, stiffnesses in different modes of deformation. The shims may either be rigid or flexible, flat or curved, but are usually close to inextensible, being made of a high modulus material such as steel. On the other hand, rubber has an exceptionally low shear modulus, about one thousandth of its bulk modulus, so that shear of the rubber layers and flexure of the high modulus layers (if thin) are the dominant mechanisms of deformation of the composite. In comparison, extension of the layers and changes to their separation are highly constrained.
Modes of failure are addressed as well as force-deformation behaviour. For compression normal to the laminations, the shear in the rubber results in in-plane tension in the shims, possibly leading to tensile failure. For tension normal to the laminations, the elastomer can cavitate, which would relieve the shear in it and hence the in-plane compressive stress applied to the shim. In flexure, shear in the rubber can apply in-plane compressive stress to the shims and cause buckling failure.