Crack propagation in thin shells by explicit dynamics solid-shell models

A computational technique for the simulation of crack propagation due to cutting in thin structures is proposed. The implementation of elastoplastic solid-shell elements in an explicit framework is discussed. Finally, in the case of crack propagation, the issue of the selection of a propagation criterion is briefly discussed. Crack propagation is modelled making use of a so called “directional” cohesive approach

Dynamic delamination crack propagation in a graphite/epoxy laminate

Dynamic delamination crack propagation in a (90/0) 5s Graphite/Epoxy laminate with an embedded interfacial crack was investigated experimentally using high speed photography. The dynamic motion was produced by impacting the beamlike laminate specimen with a silicon rubber ball. The threshold impact velocities required to initiate dynamic crack propagation in laminates with varying initial crack positions were determined. The crack propagation speeds were estimated from the photographs. Results show that the through the thickness position of the embedded crack can significantly affect the dominant mechanism and the threshold impact velocity for the onset of crack movement. If the initial delamination is placed near the top of bottom surface of the laminate, local buckling of the delaminated plies may cause instability of the crack. If the initial delamination lies on the midplane, local buckling does not occur and the initiation of crack propagation appears to be dominated by Mode II fracture. The crack propagation and arrest observed was seen to be affected by wave motion within the delamination region

Branching mechanism of intergranular crack propagation in three dimensions

We investigate the process of slow intergranular crack propagation by the finite element method model, and show that branching is induced by partial arresting of crack front owing to the geometrical randomness of grain boundaries. A possible scenario for branching instability of crack propagation in disordered continuum medium is also discussed.Comment: 4 pages, submitted to Phys.Rev.E; v2:corrected typos v3: final version to be publishe

Supersonic crack propagation in a class of lattice models of Mode III brittle fracture

We study a lattice model for mode III crack propagation in brittle materials in a stripe geometry at constant applied stretching. Stiffening of the material at large deformation produces supersonic crack propagation. For large stretching the propagation is guided by well developed soliton waves. For low stretching, the crack-tip velocity has a universal dependence on stretching that can be obtained using a simple geometrical argument.Comment: 4 pages, 3 figure

Continuum field description of crack propagation

We develop continuum field model for crack propagation in brittle amorphous solids. The model is represented by equations for elastic displacements combined with the order parameter equation which accounts for the dynamics of defects. This model captures all important phenomenology of crack propagation: crack initiation, propagation, dynamic fracture instability, sound emission, crack branching and fragmentation.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett. Additional information can be obtained from http://gershwin.msd.anl.gov/theor

Phase-field modeling and simulation of fracture in brittle materials with strongly anisotropic surface energy

Crack propagation in brittle materials with anisotropic surface energy is important in applications involving single crystals, extruded polymers, or geological and organic materials. Furthermore, when this anisotropy is strong, the phenomenology of crack propagation becomes very rich, with forbidden crack propagation directions or complex sawtooth crack patterns. This problem interrogates fundamental issues in fracture mechanics, including the principles behind the selection of crack direction. Here, we propose a variational phase-field model for strongly anisotropic fracture, which resorts to the extended Cahn-Hilliard framework proposed in the context of crystal growth. Previous phase-field models for anisotropic fracture were formulated in a framework only allowing for weak anisotropy. We implement numerically our higher-order phase-field model with smooth local maximum entropy approximants in a direct Galerkin method. The numerical results exhibit all the features of strongly anisotropic fracture and reproduce strikingly well recent experimental observations.Peer ReviewedPostprint (author’s final draft

Local dynamics of a randomly pinned crack front: A numerical study

We investigate numerically the dynamics of crack propagation along a weak plane using a model consisting of fibers connecting a soft and a hard clamp. This bottom-up model has previously been shown to contain the competition of two crack propagation mechanisms: coalescence of damage with the front on small scales and pinned elastic line motion on large scales. We investigate the dynamical scaling properties of the model, both on small and large scale. The model results compare favorable with experimental results