Numerical study on buckling of Z-pinned composite laminates

Z-pinning is a newly developed technique to enhance the strength of composite laminates in the thickness direction. Recent experimental and theoretical researches manifest that z-pins can significantly improve mode I fracture toughness in double-cantilever-beam tests and mode II fracture toughness in end-notched-flexure beam tests. From a practical point of view, buckling accompanying delamination is a typical failure mode in laminated composite structures. For the purpose of a complete understanding on the z-pinning technique towards an improvement of the mechanical behaviour of laminated composites, in the present study, a numerical approach is applied to investigate the buckling of z-pinned composite laminates with initial delaminations under compression. The numerical results indicate that z-pinning can effectively increase the compressive strength of composite laminates provided that the initial imperfection is within a certain range. The magnitude of the improvement is consistent with available experimental data.