Crack front échelon instability in mixed mode fracture of a strongly nonlinear elastic solid
INSP, Université Pierre et Marie Curie-Paris 6, CNRS, UMR 7588 - 4 place Jussieu, 75005 Paris, France
Received: 27 November 2013
Accepted: 20 January 2014
In order to assess the role of elastic nonlinearity in gel fracture, we study the échelon instability in gelatin under mixed mode tensile and antiplane shear loading —i.e. the emergence of segmented crack front structures connected by steps. We evidence the existence of an energy-release-rate–dependent mode mixity threshold. We show that échelons appear via nucleation of localized helical front distortions, and that their emergence is the continuation of the cross-hatching instability of gels and rubbers under pure tensile loading, shifted by the biasing effect of the antiplane shear. This result, at odds with the direct bifurcation predicted by linear elastic fracture mechanics, can be assigned to the controlling role of elastic nonlinearity.
PACS: 46.50.+a – Fracture mechanics, fatigue and cracks / 62.20.mm – Fracture / 89.75.Kd – Patterns
© EPLA, 2014