Z-Pinning has been used effectively for improving the delamination resistance of laminated composite structures. The pin density, diameter and length are some of the parameters related to the effectiveness of z-pins for increasing the delamination resistance. Phenomenological as well as physics-based modeling approaches have been proposed in the past to evaluate the effectiveness of z-pinning and predict the load-bearing capacity of z pinned composite structures. Recent developments with finite element based modeling techniques have introduced numerous design tools to model damage and predict the remaining useful life of composite structures. In this paper, a traction-separation based cohesive modeling approach is proposed to predict the effect of z-pinning on laminated composites. During this study, a detailed characterization of traction-separation laws to represent the frictional effect due to z-pinning is presented. Utilizing these experimental results, numerical simulation of the progressive damage due to delaminations between plies with and without z-pinning has been simulated and compared with experimental results. Details of the experimental results using double cantilever beam (DCB) tests with and without z-pinning are presented for IM7/977-3 graphite/epoxy. The modeling approach taken in this study utilizing the cohesive elements within the Abaqus® finite element software has proven that the models can predict the behavior of z-pinned composites close to experimental observations.
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