Numerical Analysis Of Mechanical Behavior Of Woven Composites Under Compression And Threaded Joints

Woven composites have been widely used in the high technology fields, such as aeronautics & astronautics etc. Compared with unidirectional fiber-reinforced laminated composite plates, on the one hand, there is great potential for woven composites to improve the interlaminar strength and damage tolerance because of the designable microstructure of composites;on the other hand, the process of fabrication of woven composites is simpler than the laminated composite plates due to the less work in the stacking and manufacturing procedure, giving very good application future.In order to connect and fix all kinds of structures, there are usually a lot of threaded joints in the 2-D woven composite structures. FEM software, ANSYS, is used to analyze the stress filed of screw joints in the middle-thick plate woven composites. The distribution of load on the threads of the screw is given. It is studied for the effects of the diameter of the screw, fiber volume fraction in the end plates and friction coefficient between screw and composite on the largest tensile stress in the round chamfer.The failure modes of woven composites are very complex because of their anisotropic constitutive relationships and undulatory microstructure of the fiber yarns. 3-D finite element analysis is applied to the compression of 2-D woven composite. The unit cell is established based on the measured microstructure parameters of the 2-D woven composites, according to the hypothesis that woven composites are composed of repeated unit cells. The mechanical properties of fiber yarns, i.e. the mechanical properties of unidirectional composites, can be obtained by previous empirical equation. Microscopic stress state after compression in the direction perpendicular to woven plane(transverse compression) and fiber yarns is analyzed in detail. For transverse compression, the maximum compressive stress of matrix is found to occur at the interlacing junctions of the fiber yarns. The analysis shows that, compared with 0°/90° laminates, the maximum interlaminar shear stress occurs on the free boundary under transverse compression for 2-D woven composites, giving a possible interlaminar crack here. That is agreement with the experiment result. The angles of the failure plane are studied in various cross-sectional dimensions and clearances between the fiber yarns. For the compression in the direction along the fiber yarns, the maximum interlaminar shear stress occurs at the interlacing junctions of the yarns.