Numerical Analysis of the Three Point Bend Impact Test for Polymers

The three point bend impact test is analysed by employing the finite volume method. Numerical modelling was necessary to enhance understanding of the test and to obtain dynamic correction functions, which are convenient to calculate K and G from measured time to fracture. A simple model of the three point bend test and a more sophisticated model, which included contact effects, were analysed. A good fit with experiments was found when using the contact model. The anvils were found to be important only at a late stage in the test. Several test parameters were varied to investigate their influence on the dynamic correction function. The contact stiffness was found to have an important influence on the shape of the dynamic correction function. Due to the nonlinear contact stiffness the impact velocity also affects the dynamic correction function. For a polymer specimen and a steel striker the specimen width and the specimen material were found to have only a small influence on the dynamic correction function. The dynamic correction function for G was found to exhibit higher oscillations than the dynamic correction function for Kas expected, and hence the former is a more sensitive parameter.