Elastic interaction of multiple delaminations in plates subject to cylindrical bending

This paper deals with the elastic interaction of multiple through-width delaminations in laminated plates subject to static out of plane loading and deforming in cylindrical bending. A model has been formulated utilizing the classical theory of the bending of beams and plates and accounting for non-frictional contact along the delamination faces. Strong interaction effects arise between the delaminations including shielding and amplification of the energy release rate and modification of the mode ratio as compared to a structure with only a single delamination. Such behavior has been summarized in maps that completely characterize the response of a system of two delaminations in a cantilever beam. The quasi-static propagation of the system of delaminations is also strongly controlled by the delamination interactions, which lead to local snap-back and snap-through instabilities, crack arrest and crack pull-along. The results show similarity to those for cracked infinite bodies, but the finite-thickness of the plate plays an important role and gives rise to more complex behaviors. The stability of the equality of length of a system of n delaminations is controlled by their spacing. Finite element calculations confirm that the model proposed here is accurate, except when the difference in the length of the interacting delaminations is less than a few times the separation of their planes.