The effect of clamping conditions on tearing energy estimation for highly stretchable materials

A typical measure for the toughness of highly stretchable materials is the energy for tearing, determined in mode I fracture tests on wide specimens with a lateral cut. In the present paper we show that, when slippage occurs in the grips that hold the specimens, the classical analysis of this test leads to an overestimation of the tearing energy, if sample stretches are determined from the grip displacements. Unlike for elastic properties, the use of local strain data retrieved by an optical measurement system does not remedy this issue but, vice versa, underpredicts the tearing energy. Here we propose a simple post hoc correction of the measured tearing energy, and an improved clamp design to prevent slippage. Applied to a commercial acrylic elastomer, the corrected tearing energy was independent of the occurrence of slippage and consistent with the result obtained with the new clamping system as well as values reported in literature.