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Strain Rate Dependence of Fracture in a Rubber-Toughened Epoxy System



D T. Raghavan, J He, Donald L. Hunston, D Hoffman


The toughening mechanisms in rubber-modified epoxies appear to be viscoelastic in nature since the fracture behavior is dependent on loading rate. This behavior has been studied and modeled only for the most common toughened epoxy system. The present work examines the loading rate effect for a new material based on acrylic rubber by measuring the fracture energy in constant cross-head speed tests conducted over a wide range of speeds. As expected, decreasing the loading rate produced an increase in toughness. Just as in the previous studies, the fracture energies could be modeled with a power law relationship when the loading rate was characterized by the time to failure. Moreover, the parameters involved in the model are quite consistent with the earlier results. For most rates, the behavior was approximately linear elastic with little or no r-curve behavior. Below a critical rate, however, there was a transition to ductile failure with a large r-curve and very high fracture energies. This transition is very sharp which may help explain why some previous studies have observed large r-curves while others have not.
Journal of Adhesion


acrylic rubber, epoxy, fracture, r-curve, rate effect, toughening, viscoelastic


Raghavan, D. , He, J. , Hunston, D. and Hoffman, D. (2002), Strain Rate Dependence of Fracture in a Rubber-Toughened Epoxy System, Journal of Adhesion, [online], (Accessed July 19, 2024)


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Created December 31, 2001, Updated October 12, 2021