A Non-Linear Viscoelastic Characterization of a Natural Rubber Gum Vulcanizate

Abstract

Abstract The utility of the generalized strain measure viscoelastic equation (the CBT theory) has been demonstrated in part by excellent agreement of experiment with pure shear predictions calculated from simple tension results. Similar successes employing the generalized strain measure have been reported elsewhere. FLV predictions also demonstrated good correlation by matching predictions based on the CBT theory. However, in order to avoid excessive sensitivity to experimental error, regression parameters appearing in the FLV theory, especially for the “third order” form, were evaluated from data first smoothed using the CBT tensile elastic equation. In the future, we expect the “third order ” form to be useful at large deformations where more regression constants are needed to adequately characterize a broad deformational domain. Predictions of the storage modulus in simple tension based on either the FLV or the CBT theory agree with experiment to within approximately 10% error. Although this error is considered good from an engineering point of view, efforts are underway to identify its origin and to reduce its magnitude. Loss modulus predictions of either theory are only in semi-quantitative agreement with experiment. The frequency response of experimental E2 values is matched reasonably well by theory, but the deformational dependence of the data is lost due to relatively large scatter.