Fatigue and post-fatigue tensile behaviour of non-crimp stitched and unstitched carbon/epoxy composites

An experimental study is described in this paper dealing with the tensile-tensile fatigue and the quasistatic post-fatigue tensile behaviour of a structurally stitched multi-ply carbon composite and the unstitched counterpart The influence of the stitching on the fatigue life and on the residual post-fatigue quasi-static properties in two principal direction is investigated The fatigue behaviour of both composites is represented by Wohler-like diagrams The damage imparted during fatigue is studied by X-ray analyses The residual mechanical properties of the fatigued composites after different number of cycles are compared in term of stiffness and strength The post-fatigue quasi-static tensile tests include acoustic emission (AE) registration and full field surface strain mapping (SM) to investigate the damage onset and development The main conclusions of the experimental work are the fatigue life is improved in the direction of the structural stitching and is reduced in the orthogonal direction for the considered cyclic stress level the post-fatigue reduction of the mechanical properties is limited by the structural stitching (C) 2010 Elsevier Ltd All rights reserved