No abstract

Working on quasi-static phase-field fracture modeling in nearly incompressible solids for crack propagation is a challenging task. To avoid arising locking effects therein, a mixed form for the solid displacement equation is developed, resulting in two unknowns: a displacement field and a hydro-static pressure variable. In order to fulfil an inf-sup condition, stable Taylor-Hood elements are employed for the displacement-pressure system. The irreversibility condition of the crack evolution is handled by help of a primal-dual active set method. To get both a sharper crack and reasonable computational costs, adaptive meshes are used based on a predictor-corrector scheme. The crack paths from the numerical simulations are compared on the experimentally observed crack paths in carbon black filled ethylene propylene diene monomer (EPDM) rubber strips. The punctured EPDM strips with a hole and a given notch at different heights are stretched till total failure.

In this work, we present crack propagation experiments evaluated by digital image correlation (DIC) for a carbon black filled ethylene propylene diene monomer rubber (EPDM) and numerical modeling with the help of variational phase-field fracture. Our main focus is the evolution of cracks in one-sided notched EPDM strips containing a circular hole. The crack propagation experiments are complemented with investigations identifying the mechanical material properties as well as the critical strain energy release rate. For simulating the evolution of cracks with a given notch, phase-field fracture modeling is a popular approach. To avoid volume-locking effects considering fractures in nearly incompressible materials, a quasi-static phase-field fracture model in its classical formulation is reformulated with the help of a mixed form of the soliddisplacement equation. The new established mixed phase-field fracture model is applied to simulate crack propagation in punctured EPDM strips by using the experimentally identified material parameters with mixed finite elements. To discuss agreements and point out challenges and differences, the crack paths, the maximal force response, the traverse displacement at the crack start, as well as force-displacement curves of the experimental and numerical results are compared.