Crack paths in fibre metal laminates: Role of fibre bridging

This paper discusses experimental results of fatigue tests performed under off-axis loading with respect to the principal direction of fibres in fibre metal laminates. The cracks in the metal layers of the FMLs do not propagate perpendicular to loading but at an angle to this orthogonal direction. Previous attempts to explain the crack path direction with established theories for predicting crack paths in monolithic metals are unable to explain the results in FMLs. This paper explains that crack paths are primarily a consequence of fibre bridging in the two directions: the direction of loading, and the direction perpendicular to loading.