A parametric study on the design of stitched laminated DCB specimens

Through-the-thickness stitching has been shown to have the capacity of improving the poor interlaminar toughness of laminated composites for many years. Double cantilever beam (DCB) testing has been used to assess the enhanced delamination toughness of stitched laminates. To avoid the premature flexure failure of delaminated substrate beams, thick tabs are bonded to either side of the standard DCB specimens. Consequently, higher opening load can be applied to the stitched tabbed DCB (TDCB) specimens to propagate the delamination crack due to the enlarged bending stiffness and strength. This creates a significant bending of the loading pin, which needs to be accounted for in the numerical analysis. In this paper, a parametric analysis was conducted to investigate the effect of reinforcing tab thickness on the measured and predicted delamination toughness.