Suppression of delaminations in curved structures by stitching

A simple approach is presented for analysing the effects of stitching on the mechanics of delamination failure in curved structures subjected to opening bending moments. Advantage is taken of the existence of a steady-state cracking configuration which is amenable to analysis and yields conservative design limits. Design rules are derived for the minimum stitch density required to suppress delamination crack growth and to ensure the integrity of the stitches. The rules involve only geometrical factors and material parameters that are known or readily measured. Populations of initial delamination flaws are shown to be unimportant as long as they fall beneath a threshold length of several mm. An analytical result for delamination crack growth under cyclic loading is also derived.