Effect of stitch distribution on mode I delamination toughness of laminated DCB specimens

A new nonlinear finite stitch element is proposed for parametric analysis on the effect of distribution of through-thickness stitching reinforcement on improving the delamination crack growth resistance in double cantilever beam (DCB) specimens. Both the classical and Timoshenko beam theories are used to analyze the DCB specimens. A novel two-node rod element is developed to model the stitches along the crack plane and the micromechanical stitching models available in the literature are adopted to simulate the mechanical behavior of the stitches. The bridging traction of each discrete stitch is simulated as a nonlinear spring. The numerical examples show that stitch distribution can significantly affects the improvement on delamination crack growth resistance in DCB specimens. When keeping the stitch density or stitch volume fraction as a constant, the stress intensity factor at the delamination crack tip can be significantly affected by altering the stitch distribution along the crack plane.