A comment on ‘The trousers fracture test for viscoelastic elastomers’, JAM 90(7), 071010, 2023

The Rivlin-Thomas classical energy balance model for tearing tests suggests that the fracture energy G is proportional to the work of the external load in the legs (potential energy), for not too large stretches in the legs, so the increase of G with loading rate is observed or measured, but not really explained by the model. Shrimali & Lopez-Pamies (SLP) have recently built a theory on viscoelastic fracture from recent experimental evidence of a critical (stretch rate independent) stretch on nucleation of cracks in pure shear tests. The theory in other words incorporates this evidence in an otherwise energy based criterion. In the paper “The trousers fracture test for viscoelastic elastomers”, JAM 90(7), 071010, 2023, they seem to obtain the critical (stretch rate independent) stretch condition for the case of trouser tests (applying their theory from a long enough crack) both in nucleation and steady state propagation. This outcome seems reasonable since for a linear material, looking at the elastic limit cases of very slow and very fast rate it would produce an increase of the load, and hence of the fracture energy, proportional to the increase of the modulus, which is in line with what has been found experimentally, although possibly in contrast with classical theories.