Orifice Stitched Reinforced Composite Materials, Experimental Research And Numerical Simulation

Due to drilling, fiber/matrix splitting, fiber breakage and ply delamination near the hole may influence seriously the mechanical behaviour of laminates with open holes. The recent success in the development of stitched composites is a result of stitching technology through the thickness of laminated composites containing open holes. The stitching reinforcement exhibit fine prospects for composite structure containing stress concentrations. They can slow down the stress concentrations near the hole, give rise to interlaminar strength and delamination resistance, improve the strength of composite structure with holes.Experiment studies were carried out on the effect of stitching reinforcement for composite laminates containing a circular hole. The effects of stitching parameters, such as stitching needle distance, row spacing, edge distance, single stitching or double stitching, etc., were compared and analysed. The tensile strength and stiffness were measured for composite laminates containing a circular hole. The strain concentration and strain distribution regularity were investigated analytically and experimentally. The hole edge coefficient of strain concentration were measured for different stitching parameters, external load, the edge location of hole, etc. The experimental results showed a distinct efficiency of stitching reinforcement for composite laminates containing a circular hole and gave a design method about stitching on the edge of hole.The theoretical calculation method for stress concentrations in anisotropic plates with a circular opening was spread to composite laminates with a circular opening. Based on the classical laminated plate theory, a finite composite laminate with a circular opening was treated as an anisotropic plate. Then the anisotropic plate equivalently was transformed into a single-oriented fibers plate subjected to off-axial loading. Finally the stress concentration factors of composite laminates with a circular opening can be obtained by means of a similar calculation formulas for the stress concentration factor in the single-oriented fibers plate subjected to off-axial loading. Using the derived expressions, the effects of the related parameters, such as diameter (opening) - to -width (plate) ratio d/w, fiber layups, constant of material property, etc on stress concentration were compared and analysed .The application of the finite element method was also briefly reviewed, and a brief...