FRACTURE OF NON-LINEAR BIOLOGICAL-MATERIALS - SOME OBSERVATIONS FROM PRACTICE RELEVANT TO RECENT THEORY

A recent theoretical analysis of the effects of non-linear elasticity on the toughness of biological materials as measured by tear tests emphasises the importance of considering energy storage in the legs of the test piece. This is supported here by reference to practical results on tearing biological tissues. The load-deformation curves are shown for tear tests on four different biological materials; (a) the mesogloea (body wall connective tissue) from a sea anemone, (b) rat skin, (c) pig aorta (the main artery coming out of the heart) and (d) cooked meat (beef semitendinosus muscle cooked to 80 °C). All four curves display an initial J-shaped pre-tearing region followed by a 'plateau' in which slow crack propagation takes place with marked oscillations in the