Journal Papers Published by the Rubber Research Group
"A new approach to characterize the onset tearing in rubber."
Journal: Constitutive Models for Rubber VII edited by S. Jerrams and N. Murphy
Since Rivlin and Thomas (1953) the tearing behaviour of rubber has been characterized using fracture mechanics, whereby the rubber has a geometrically independent relationship between the crack growth rate during tearing versus strain energy release rate. This approach works well under conditions of steady tearing when the crack growth rate is easy to measure. However, this approach is much harder to interpret under conditions where the rubber exhibits discontinuous crack growth behaviour such as knotty tearing or stick slip tearing. This type of tearing often arises for filled rubbers and for rubbers that strain crystallize. The measured crack growth rate is now an average of a very rapid tear rate and a zero velocity tear rate. Sakulkaew et al. (2010) developed a new approach that characterizes the rate of increase in the strain energy at the crack tip just immediately before the onset of tearing in a trouser tear test piece. This is measured directly as the time derivative of the strain energy release rate . In this work the critical strain energy release rate Tcrit to propagate the tear relationship with is examined for a range of natural rubber compounds. The aim being to demonstrate the geometric independence of this relationship to verify that the behaviour measured using a trouser tear test piece produces a similar relationship to that measured using a pure shear tear test piece.