STUDY ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MULTI - AXIS THREE - DIMENSIONAL Woven COMPOSITES

Three dimensional woven textile composites have developed rapidly, the common three dimensional woven reinforcements conclude angle interlocking structure, three direction orthogonal structure and multi axial woven structure. Researchers have been trying to add the off-axis yarn system in traditional three-dimensional woven structure, improving the in-plane performance of the composite. A new type of multi axial 3D woven composites has been developed by the Institute of Composite Materials from Tianjin Polytechnic University, the microstructure and mechanical properties of the composites are studied systematically in this paper. The main contents are as follows:(1) Based on the actual structure of 3D multi axial woven composite characters and reasonable assumptions, the mesoscopic structure unit has been build. The change trend of yarn cross-section shape, weaving material thickness, mass per unit area and the fiber volume fraction value are analyzed by the character of off-axis yarn parameter, such as the position and fiber volume fraction. These provide a basic work for the design of structural parameters of multi axial 3D woven composites.(2) According to the characteristics of multi axial 3D woven reinforcement, the position and fiber volume fraction of off-axis yarn are selected as structure factors for different structures. The solid model of meso structure is built by using 3D drawing software (UG), then period mesh and boundary conditions are set in the professional software HyperMesh, the ABAQUS software is introduced finally for elastic constants calculation and performance analysis. The elastic constants of the element and microscopic stress distribution under different loading conditions are discussed, in order to find the affection of off-axis yarn content on the elastic properties.(3) By using the longitudinal tensile, three-point bending, short beam shear and hammer vibration test methods, the mechanical properties of multi axial 3D woven composites are studied with different position and fiber volume fraction of off-axis yarn. When the off-axis layer is placed on the surface of the material, the tensile and shear properties of the 3D multi axial woven composite are better, while the bending properties and shear properties of the materials can be improved by increasing the fiber volume fraction of off-axis yarn.(4) Basic on the study of composite plant, a rectangular section unit has been analyzed. The multi axial 3D woven composites pipe units with different angle of off-axis yarn are discussed, which may be a prepared work for a further research work of pipe component design.