Seminar Spagnoli

Failure mechanisms in soft elastic materials: tearing and puncturing

Andrea Spagnoli

University of Parma, Italy

10th October 2025, 11:00-12:00 CEST, Room B-366 @ Thákurova 7, 166 29 Prague 6

Abstract: The topic of fracture mechanics in soft solids is relevant for a large class of materials, such as polymers, biomacromolecules, colloids, membranes, liquid crystals, granular matter, soft interfaces, complex fluids, surfactants, gels, nanomaterials, foams, silicones, biological tissues, etc. In the present seminar we discuss the extraordinary tearing resistance of soft solids, attempting an interpretation of this distinguishing feature by presenting a simplified model to describe elastic crack-tip blunting. Firstly, for incompressible hyperelastic solids the characteristics of crack profiles, obtained by means of detailed FE simulations, are discussed in relation to the material strain hardening. Then, the proposed model is employed to derive an analytical description of the progressive non-linear decrease of the crack tip curvature under loading, assuming a finite deformation of the solid surrounding the crack. Some experimental tests on silicone cracked specimens demonstrate the validity of the analytical model in predicting the flaw tolerance in the material. Fracture is a key behavioural feature when dealing with the mechanical problem of a foreign object penetrating into a soft material, due to the inevitable laceration of the target solid involved. We discuss the resistance to penetration of a rigid puncturing needle into a solid block. A theoretical model validated by FE simulations and proof-of-concept experiments is presented.

Andrea Spagnoli is full professor in Solid and Structural Mechanics at University of Parma, Italy. Andrea Spagnoli earned his PhD at Imperial College, London in 1997, discussing a thesis on the stability of shell structures. In the past two decades, his research interests have dealt with a variety of theoretical and numerical aspects related to fracture mechanics and fatigue of engineering materials and structures. More recently he started working on the mechanics of soft materials, including advanced polymers and biological tissues. Editor of the journal Fatigue and Fracture of Engineering Materials and Structures; member of the editorial board of the Int. J. Solids and Structures, Int. J. Fatigue, Fatigue and Fracture of Engineering Materials and Structures. Author of 120+ papers on peer-reviewed journals, with 3700+ citations (h-index=35).