Progressive failure analysis of z-pin reinforced composite pi joints

Abstract

A finite element model of a z-pin reinforced composite pi joint has been developed and correlated against experimental results. A smeared cohesive zone modeling approach was implemented to represent the effect of z-pinning in an efficient and scalable manner. In the smeared approach, cohesive properties governing the traction–separation response of the z-pin reinforced areas were defined to account for the effective fracture toughness caused by z-pinning in an averaged sense. The crack band method was used to account for diffuse damage and failure in the weave of the pi preform. The damage in the preform developed due to delamination suppression caused by the z-pinning. The numerical model was calibrated using experimental data from pristine and defective z-pinned pi joints subjected to pull-off and side-bend loading. Comparisons of experimental and numerical results show good agreement in terms of structural response, critical loads, and failure modes.