Biaxial Simple Shear of Rubber

Because the shear modulus is about 3 orders of magnitude less than the bulk modulus of rubber, the local state of strain of rubber in most engineering components approximates to simple shear. For rubber-steel laminates, the shear strain is approximately uniform, and stiffness is not affected by "shape factor" if the rigid inserts move parallel to each other, whereas the shear strain is non uniform and a the stiffness is affected by shape factor if the rigid inserts move orthogonal to their plane so that the thickness of the rubber layer is changed. The general local state of rubber in most engineering components therefore approximates to biaxial simple shear. 

Experimental results are reported for rubbers with and without reinforced filler in uniaxial simple shear, with the direction of shear strain varied throughout possible directions in the plane of the shear disc, and in a range of biaxial simple shear deformations, using a technique in which two arbitrary orthogonal shear strains may be applied simultaneously. The results are compared to the predictions of selected time domain stress-strain models, and the implications for the behaviour of rubber in biaxial simple shear and the type of model that might describe such behaviour are discussed.