Predicting and Designing Failure in Soft Materials

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Fracture toughness is usually reported as a material property, yet the same soft polymer can fail in rather different ways depending on what multiphysics field is applied to it, how its network was crosslinked, and what touches its surface. This raises the following question: what actually sets failure in a soft polymer, and can we predict it well enough to design it? This talk looks at a few of those dependencies with bespoke predictive continuum mechanics-based frameworks, informed by experimental observations. In ultra-soft magnetorheological elastomers of a stiffness of around 1 kPa, remanent magnetization induces compressive stresses that reduce stress concentration at the crack tip and delay propagation. Large deformation also allows less familiar fracture modes, among them sideways cracking, where the crack deviates to run along the loading direction rather than perpendicular to it in a PDMS elastomer. A continuum phase-field model links critical energy release rate and crosslink density to design fracture-tolerant soft heterogeneous structures. Predictions of this kind depend on the assumed crack driving force and constitutive law, which motivates approximating the J-integral at large strains through the Configurational Force Method, and identifying data-adaptive spline-based strain-energy functions from experiments rather than choosing them beforehand. These threads come together in soft cutting, where failure is imposed by a blade in contact. A gelatin hydrogel, an elastomer and a meat-based material show three different cutting regimes, which a coupled cohesive-zone and contact model helps to separate. By unifying fracture, normal contact, tangential friction, and adhesion, the framework explains mechanisms in cutting of soft matter. Looking ahead, this framework provides a basis for a research program on soft cutting in multiphysics and heterogeneous materials. At TU/e, I would combine continuum mechanics-based and multiscale modelling with advanced mechanical characterization, imaging, and rheology to connect material architecture and interfacial processes to macroscopic cutting response. This direction would create opportunities for collaboration across the Processing and Performance of Materials, Mechanics of Materials, and Microsystems sections, as well as the Department of Biomedical Engineering, with applications ranging from bio-inspired materials and hydrogels to food processing and flexible electronics.

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