Failure Properties of Filled Elastomers as Determined by Strain Endurance Tests

Abstract

Determination of the resistance of a material to failure when held at constant strain for an extended period of time is of great practical importance. For elastomers the failure properties are usually described by the well known Smith’s “failure envelope”. This failure envelope is accepted to be independent of the kind of experiment used for its determination and is applicable in all cases in which the material remains basically (chemically and physically) unchanged during the period of investigation. In reality almost all elastomers fail as a result of their stress or strain history. During this history the load changes and the material has to withstand different stresses for long periods of time. Simultaneously the material ages and internal structural changes may occur. These aging effects are probably accelerated due to the fact that the material is kept deformed and its internal energy is higher than in the case of an unstrained system. Thus, the real failure properties of a material which is being used can not be probably represented by a failure envelope determined by testing of unaged materials only.