Validating Griffith fracture propagation in the phase-field approach to fracture: The case of Mode III by means of the trousers test

TL;DR

This paper demonstrates that the phase-field approach accurately models Mode III fracture propagation in the trousers test, aligning with Griffith energy principles, and highlights limitations of classical analysis formulas.

Contribution

It provides the first validation of phase-field fracture propagation in Mode III and compares it with Griffith theory, also revealing limitations of classical formulas.

Findings

Phase-field approach successfully predicts Mode III fracture propagation.

Comparison with Griffith energy confirms model accuracy.

Identifies limitations of classical analysis formulas.

Abstract

At present, there is an abundance of results showing that the phase-field approach to fracture in elastic brittle materials -- when properly accounting for material strength -- describes the \emph{nucleation} of fracture from large pre-existing cracks in a manner that is consistent with the Griffith competition between bulk deformation energy and surface fracture energy. By contrast, results that demonstrate the ability of this approach to describe Griffith fracture \emph{propagation} are scarce and restricted to Mode I. Aimed at addressing this lacuna, the main objective of this paper is to show that the phase-field approach to fracture describes Mode III fracture propagation in a manner that is indeed consistent with the Griffith energy competition. This is accomplished via direct comparisons between phase-field predictions for fracture propagation in the so-called \emph{trousers} \emph{test} and the corresponding results that emerge from the Griffith energy competition. The latter are generated from full-field finite-element solutions that -- as an additional critical contribution of this paper -- also serve to bring to light the hitherto unexplored limitations of the classical Rivlin-Thomas-Greensmith formulas that are routinely used to analyze the trousers test.