J-shaped stress/strain curves and crack resistance of biological materials

Abstract

The influence of the stressistrain curve shape on the cracking of a brittle elastic material is analysed in terms of the energy balance theory of fracture mechanics. Both r-shaped and J-shaped elastic curves are investigated. For some cracking tests, for example the trouser tear and lubricated cutting tests, the shape of the stressistrain curve is found to have little effect on the crack extension force; this is determined mainly by the fracture surface energy of the material. However, in other tests such as tension, the shape of the stressistrain curve does influence the fracture stress, but not by a large amount when compared with the effect of reinforcement. Whether an r-shaped or J-shaped curve leads to a higher fracture stress depends on such factors as the fracture energy and the size of the preexisting crack. It thus appears that no general statement can be made about the effect of the shape of the stressistrain curve upon the crack resistance of materials, contrary to views expressed previously in the literature.

Characterization of fracture toughness exhaustion in pig aorta

“…Some of these include tearing tests using a variety of sample shapes in different configurations like ''trousers'', ''pure shear'', ''angled'' and ''split'' (Lake, 2003). Other methods use a sharp instrument to induce fracturing, such as the scissor test (McCarthy et al, 2007;Pereira et al, 1997) and assorted cutting tests with or without lubrications, like guillotines and similar bladed devices (Atkins and Mai, 1979;Darvell et al, 1996;Kendall and Fuller, 1987). For this study, a lubricated cutting test (guillotine) (controlled crack propagation under Mode 1) has been selected to assess fracture toughness.…”

Adhesion and composites

“…His adhesion experiment is easily demonstrated by peeling 'cling-film' from a glass oven dish. Frictionless cleavage of an adhesive joint follows the same equation [37]. In more complex situations, where the joint is stretched significantly during breakage as in the lap joint of Fig.…”

Characterization of aortic tissue fracture toughness and stiffness under cyclic fatigue loading

“…Some of these include tearing tests using a variety of sample shapes in different configurations like "trousers", "pure shear," "angled," and "split" [95]. Other methods use a sharp instrument to induce fracturing, such as the scissor test [78,96] and assorted cutting tests with or without lubrications, like guillotines and similar bladed devices [71,74,97]. Common to all these tests is that forces exerted on the sample and the displacement of the force-inducing actuators are recorded as the crack advances, thus providing a measure of the energy flux into the system.…”