Fiber and continuum scale contributions to the intrinsic and apparent fracture of soft collagenous tissue via cutting.

Abstract

Soft collagenous tissues inspire material design because of their excellent fracture properties. Their fracture is integral to surgical procedures and unavoidable in many forms of trauma and disease, yet measuring it remains challenging. Sample size limitations and emergent, strain-induced anisotropy increase boundary condition effects within classic test geometries, prohibiting cross-study comparison. Further, classic tests can neither sense internal heterogeneities nor disentangle their energetic contributions to the apparent fracture energy. Leveraging in situ microstructural observations from second harmonic generation imaging, we demonstrate that Y-shaped cutting addresses these limitations in bovine Glisson's capsule (bGC). We show cutting's sensitivity to tissue heterogeneity through characterization of bGC's sawtooth cutting force. We also report a boundary-condition-independent, intrinsic cutting energy for bGC in phosphate buffered solution (PBS). At 276 ± 17 J m^-2, it is surprisingly lower than expected. Contextualizing bGC response against commercial silicone, we show that its excellent failure behavior arises primarily from management of stress concentration near the crack tip over a characteristic microscale, rather than from an unusually high intrinsic fracture energy.