Puncturing of soft tissues: experimental and fracture mechanics-based study

The integrity of soft materials against puncturing is of great relevance for their performance because of the high sensitivity to local rupture caused by rigid sharp objects. In this work, the mechanics of puncturing is studied with respect to a sharp-tipped rigid needle with a circular cross sectio...

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Bibliographic Details
Published in:Soft matter 2023-05, Vol.19 (2), p.3629-3639
Main Authors: Montanari, Matteo, Brighenti, Roberto, Terzano, Michele, Spagnoli, Andrea
Format: Article
Language:English
Subjects:
Crack propagation
Failure modes
Finite element method
Fracture mechanics
Fracture toughness
Linear elastic fracture mechanics
Needles
Propagation modes
Silicones
Soft tissues
Stiffness
Strain energy
Two dimensional analysis
Two dimensional models
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Summary:The integrity of soft materials against puncturing is of great relevance for their performance because of the high sensitivity to local rupture caused by rigid sharp objects. In this work, the mechanics of puncturing is studied with respect to a sharp-tipped rigid needle with a circular cross section, penetrating a soft target solid. The failure mode associated with puncturing is identified as a mode-I crack propagation, which is analytically described by a two-dimensional model of the target solid, taking place in a plane normal to the penetration axis. It is shown that the force required for the onset of needle penetration is dependent on two energy contributions, that are, the strain energy stored in the target solid and the energy consumed in crack propagation. More specifically, the force is found to be dependent on the fracture toughness of the material, its stiffness and the sharpness of the penetrating tool. The reference case within the framework of small strain elasticity is first investigated, leading to closed-form toughness parameters related to classical linear elastic fracture mechanics. Then, nonlinear finite element analyses for an Ogden hyperelastic material are presented. Supporting the proposed theoretical framework, a series of puncturing experiments on two commercial silicones is presented. The combined experimental-theoretical findings suggest a simple, yet reliable tool to easily handle and assess safety against puncturing of soft materials. Penetration of a rigid circular needle into soft target solids is studied combining closed-form solution based on linear elastic fracture mechanics, FEM simulations and experiments. The results provide a manageable tool to assess safety of soft materials against puncturing.
ISSN:1744-683X
1744-6848
DOI:10.1039/d3sm00011g