Verification of hyperelastic test methods.

Abstract

Commercial finite element analysis (FEA) software packages are used extensively for the prediction of the performance of adhesive joints. The accuracy of any prediction will depend on the validity of the material model employed and the reliability of the test data input into the chosen model. Methods for obtaining design data for flexible adhesives are being investigated in Project PAJ1. The hyperelastic material models being investigated for characterising flexible adhesives require input data measured under conditions of plane strain and equi-biaxial tension. Studies verifying the test methods, developed in PAJ1, for generating these data are described in this report. The lap joint specimen used in PAJ1 has been further investigated. 3-D FEA has been used to explore the effects of misalignment of the test specimen. The force-extension response will be little affected. However, peel stresses will be greatly increased. This may lead to premature failure of the specimen. The studies described in this report have cleared up some of the uncertainties identified in earlier studies. The measurement methods employed have now been validated and better measurement practices identified. Therefore, future studies can be carried out with more confidence in the reliability of the test data.