DELAYED FRACTURE OF AN INHOMOGENEOUS SOFT SOLID

The spontaneous fracture of polymer gels was studied. Contrary to crys talline solids, where fracture usually happens instantaneously at a we ll-defined breaking strength, the fracture of a polymer gel can occur with a delay. When a constant force was applied, the cracks nucleated and started to propagate after a delay that can be as long as 15 minut es, depending on the force. This phenomenon can be understood by calcu lating the activation energy for crack nucleation in arbitrary dimensi on and accounting for the inhomogeneity of the gel network in terms of its fractal dimension.