Tear resistance of soft collagenous tissues

Abstract

Fracture toughness characterizes the ability of a material to maintain a certain level of strength despite the presence of a macroscopic crack. Understanding this tolerance for defects in soft collagenous tissues (SCT) has high relevance for assessing the risks of fracture after cutting, perforation or suturing. Here we investigate the peculiar toughening mechanisms of SCT through dedicated experiments and multi-scale simulations, showing that classical concepts of fracture mechanics are inadequate to quantify and explain the high defect tolerance of these materials. Our results demonstrate that SCT strength is only modestly reduced by defects as large as several millimeters. This defect tolerance is achieved despite a very narrow process zone at the crack tip and even for a network of brittle fibrils. The fracture mechanics concept of tearing energy fails in predicting failure at such defects, and its magnitude is shown to depend on the chemical potential of the liquid environment.

On the defect tolerance of fetal membranes

“…Crack propagation initiation in mode I fracture tests was identified from top-view images, allowing the quantification of local failure stretch l F and tension. The classical method described in [26] was adapted [20,23,27] in order to quantify the apparent membrane tearing energy for soft tissues…”

“…For the inflation experiments, 8 ml min 21 of liquid was pumped into the inflation cylinder until tissue rupture. The corresponding burst pressure was recorded and the critical in-plane stretches were extracted from analysis of the top-view images [23,34], evaluated based on a reference configuration for a tension of 0.0021 N mm 21 (cf. [6]).…”

“…figures 1b and 2b) or as representative areal elements under homogeneous loads. The influence of each parameter of the DNM was systematically investigated in our previous studies [3,9,23]. The proposed parameter set represents the best fit to the measured uniaxial and multiaxial deformation behaviour of AM (cf.…”

“…. ., N. The fibres are assumed to be embedded in a compressible matrix and the overall strain energy in terms of the left Cauchy-Green tensor b, its determinant J 2 ¼ det b and l f i reads C ¼ m 0 (e qg 2 1)/(2q), with [33,38] Hs, where s is the Cauchy stress tensor, H is the AM thickness in the initial state and l 3 is the stretch in the membrane normal direction [23]. Computations were performed in Abaqus with a user subroutine for the material model, using three-and four-node elements in plane stress state (CPS3, CPS4), and the results were analysed in consideration of a reference tension corresponding to the one applied in the experimental procedure.…”

Injectable Biomedical Devices for Sensing and Stimulating Internal Body Organs

“…To provide a design guideline of penetrating probes, a schematic illustration showing the relevant parameters during the penetration process is presented in Figure a. Also, Figure 3b summarizes the elastic modulus and ultimate tensile strength of the representative organs of our body 64–69. As there are only a few studies on fracture toughness and fracture nucleation energy of human organs, ultimate tensile strength is summarized which can be used to estimate the toughness 65,66,70–87…”