Abstract: Debonding along the propellant/liner interface is one of the major forms in which rocket motor structural integrity can fail. The double cantilever sandwich beam experiments are performed to investigate the mode-I fracture of HTPB propellant/ linear interface. These experiments show that a craze damaged zone which is consisted of voids and fibers exists in the crack tip.The crack initiation and extension are essentially to be local crazing initiation, thickening and micro-fiber fracture.The failure mechanism of the interfacial debond is the growth and coalescence of near-tip voids, while the typical fracture mode of the interface includes the cohesive failure within the adhesive, interfacial failure and mixed failure. The shape of the damaged zone ahead of the crack tip is found to be related to the constraints imposed by the adjacent components when the crack propagates stably. The concept of the effective crack length could be used to eliminate the effects of the plastic deformation and blunting ahead of the crack tip on the fracture energy.

Key words: ordnance science and technology, propellant/liner interface, crack initiation, crack extension, double cantilever sandwich beam