ABSTRACT
The concept of complex modulus was developed with the goal of characterising the steady state response of materials to sinusoidal strain, originally in the context of linear viscoelasticity. Experiments have been carried out using cyclic shear deformations of a filled styrene-butadiene rubber material and capturing detailed stress-strain data especially for the transient phenomena at the transition from one amplitude to another. During the course of work on modelling the results of an experimental characterisation of filled rubber the effect of change in amplitude on the dynamic stiffness was discussed, but the detailed behaviour following a reduction in amplitude of a sinusoidal excitation was not at that time addressed. Generalised Maxwell models are often used for inelastic material behaviour. With such models, steady-state sinusoidal stress-strain loops are always perfect ellipses, if the elements are linear. For a given frequency, the gradient and proportions of these ellipses are independent of amplitude, leaving no possibility of the Fletcher-Gent effect.
