Effect of Stacking Sequence on Open-Hole Tensile Strength of Composite Laminates

The effect of a ply stacking sequence on the open-hole tensile strength of composite laminates has been investigated both numerically and experimentally. A finite element technique has been developed that includes the subcritical damage within and between the plies. It is thus able to capture, in some detail, the effects of variation in stacking sequence. All possible permutations of 0, 90, and 45 deg plies in a quasi-isotropic layup have been analyzed. Variations in strength have been observed and explained in terms of subcritical damage development. Two stacking sequences showing different behavior were chosen for scaling in the thickness direction by increasing the ply thickness. Analysis of the first predicted a significant decrease in strength and a change in failure mode from fiberdominated to delamination-dominated failure with increasing thickness. The second predicted no such decrease in strength or change of failure mode. Both of these stacking sequences were then tested experimentally at both thicknesses, and excellent agreement with the numerical models was obtained, both in terms of damage mode and failure stress.