Roughening of a propagating planar crack front

A numerical model of the front of a planar crack propagating between two co nnected elastic plates is investigated. The plates are modeled as square la ttices of elastic beams. The plates are connected by similar but breakable beams with a randomly varying stiffness. The crack is driven by pulling bot h plates at one end in Mode I at a constant rate. We find zeta=1/3, z=4/3, and beta=1/4 for the roughness, dynamical, and growth exponents, respective ly, that describe the front behavior. This is similar to continuum limit an alyses based on a perturbative stress-intensity treatment of the front [H. Gao and J. R. Rice, J. Appl. Mech. 56, 828 (1989)]. We discuss the differen ces to recent experiments.