Material BehaviourThe viscoelastic behaviour of rubber under a small simple shear oscillation superimposed on a large pure shear

Previous papers have reported measurements of the viscoelastic behaviour of rubber as a function of a large tensile pre-strain superimposed with an additional much smaller torsion or tension oscillation. It has been shown that the loss modulus, calculated using the dimensions of the test piece after the application of the pre-strain, is independent of pre-strain and is also isotropic for most of the engineering strain range and for most filled and unfilled elastomers. This has been further investigated here using a new and totally different test piece geometry, whereby a static pure shear is superimposed with a small strain additional simple shear oscillation. The results confirm the conclusions of the previous work and show that the loss modulus G″ calculated relative to the pre-strained test piece dimensions is virtually independent of the amount of the pre-strain over the majority of the engineering strain range for unfilled rubber and for rubber compounds containing carbon black fillers. This is of potentially great importance to help a design engineer understand how to calculate energy dissipation in a rubber component and to allow a more detailed examination of the fundamental energy dissipation mechanisms to be made.