Viscoelastic behavior of rubber under a complex loading

Abstract

In the literature, the loss factor of an elastomer, expressed as tan d, has been reported to decrease with strain. This has been interpreted as a lowering of the internal viscosity due to chain orientation under strain. This contrasts with experimental findings showing that up to large strains, loss modulus does not change with strain. These experiments show that, as measured, tan d does decrease with strain. However, a simple analysis shows that this effect is due to geometric changes alone and that the essential viscoelastic behavior, expressed as the loss modulus, is constant with strain up to an extension of about 2 for the simple unfilled compounds investigated here. This article also shows that the prestrain does not induce any significant anisotropy in the loss modulus, at least up to an extension ratio of 2. This was measured by the stretching of a rubber sample by simple extension and then the subjection of the sample to free vibrations in either torsion or tension. By the measurement of the damping in this way, the anisotropy induced by the preextension was measured. The experiments in this work were all conducted on unfilled natural rubber or styrenebutadiene rubber compounds, with 2 different natural rubber compounds being used to investigate the effect of the crosslink density.

The viscoelastic behavior of rubber under a complex loading. II. The effect large strains and the incorporation of carbon black

“…Suphadon et al3 found for unfilled rubbers the loss modulus calculated with reference to the deformed dimensions of the test piece after prestraining was independent of prestrain for extension ratios less than 2 and was the same whether measured using the torsion oscillation (out of plane with the prestrain) or the tension oscillation (in plane with the prestrain). This work extends this earlier work to prestrains greater than two and also examines the behavior in filled rubbers.…”

“…The method whereby a sample prestrained in tension has an additional small torsion oscillation superimposed has been adopted previously by several researchers17–21 and again recently by Suphadon et al3 A suitable schematic for the test is shown in Figure 1. The base of the rubber cylinder was fixed and the top was mounted to a torsion inertia bar.…”

“…Busfield et al1 and Davies et al2 studied the dynamic behavior of prestrained strips of rubber subjected to tensile oscillations. Suphadon et al3 adopted this approach to study the anisotropy in the viscoelastic behavior resulting from the application of the prestrain. For unfilled rubber, at preextension ratios less than two where the storage and loss modulus are both calculated relative to the prestrained dimensions of the test piece, the loss modulus is seen to be independent of the prestrain and the energy dissipation depends upon the loss modulus and the test piece geometry alone.…”

On the Role of Both Polypropylene Fibers and Silica Nanoparticles on the Viscoelastic Behavior of Silicone Rubber Nanocomposites

“…This is why investigation of this behavior seems to be vital. Dependency of polymer properties to time and temperature causes to make complex characterization of their behavior [2][3][4]. Compression set and dynamic mechanical analysis (DMA) are some ways of studying viscoelastic behavior of polymers.…”

“…So, they can behave as an elastic solid or a viscous liquid and obey from both Hookean and Newtonian law. By applying a load to a polymer, the elastic part retains the energy and releases it after removing the load, unlike viscous part which dissipates this energy [1][2].…”