Fracture in soft elastic materials: Continuum description, molecular aspects and applications

A large class of materials, including polymers and biological tissues, exhibits the common feature of high deformability under mechanical stimuli with minimum damage, helping to achieve an extraordinary fracture toughness. In this chapter, a state of the art on mechanics and fracture of soft elastic materials is presented, deliberately neglecting time dependence and other dissipative mechanisms. The role played by large deformations is discussed following a continuum-scale description. In particular, analytical solutions of the singular near-tip stress fields for incompressible hyperelastic cracked solids are thoroughly illustrated together with solutions coming from detailed finite element models. Elastic crack blunting—a distinguishing feature of fracture behavior in soft materials—is described with respect to strain hardening and flaw tolerance of the materials. The effect of blunting is also discussed with respect to the application of fracture mechanics principles to the process of cutting in soft elastic materials. Other relevant applications being presented in this chapter are related to experimental methods to measure the fracture toughness of soft matter. Finally, a molecular-scale description of polymer-like soft materials typically characterized by a microstructure made of long polymeric chains is presented, in order to provide an insight into the inherent microscale mechanisms leading to damage and fracture of these materials.