Failure initiation in composite structures under low-velocity impact: Analytical studies

This paper presents an analytical model for the response of rectangular, specially orthotropic, symmetric laminated composite plates simply supported on all four sides subjected to low-velocity impact at the midpoint of the plate. The analysis is based considering both global and local effects. The influence of through-the-thickness normal stress on the magnitudes of inplane stresses is also considered. The plate is impacted by an impactor with a hemispherical tip. Contact force at the impact point, lateral displacements and velocities of the plate and the impactor and the stress state within the plate have been determined using modal solution technique. The governing equations, which apply to small deflection elastic response of specially orthotropic laminates, include combined effects of shear deformation and rotary inertia and non-linear Hertzian contact law. Inplane and interlaminar failure functions have been determined using quadratic failure criteria. Based on failure functions, damage initiation in the form of yarn/fiber breakage has been predicted. In general, it is observed that overall failure function is lower for woven fabric composites than for crossply laminates made of unidirectional layers.