The Study On The Mechanical Properties Of Multi-Axial Warp Knitted Fabric And The Processing Properties Of Composites

The interweave crimp of woven fabric is a factor of influencing the tensile stiffness and strength of woven fabric and its reinforced composite because of the skewness of warp and weft yam. Contrary to the construction of woven fabric, the warp(0°), weft(90°)and bias(±θ)yams are held together by a chain or tricot stitch through the thickness direction in multi-axial multi-layer warp knitted(MMWK)fabric. There are no crimps in warp, weft and bias yam in MMWK fabrics. Hence the tensile stiffness and tensile strength will reach to the maximum value compared with other kinds of fabrics.Multi-axial warp knitting machine uses warp knitting technique to bend fabric reinforced polymer laminates according to the requirement of the warp knitting fabric.This article introduced the construction of rnulti-axial warp knitting fabric as well as the production equipment, and analyzed the present application situation and development trend of multi-axial warp knitting machine at home and abroad. Through changing the fabric processing parameters, we product some MWK fabrics meeting the requirements of the fabric. We injected epoxy resin into MWK fabrics by using Vacuum Assist Resin Transfer Molding(VARTM) technology. Resin flowing behavior in the preform was recorded in detail, and results indicates that stitching loop, stitch density, the number of plies influence resin flowing in preform as well as other stitching parameters with the same condition, which can be obtained in this paper.In this paper, we have cut fabrics and plates into the test size with reference to test method for tensile of woven fabrics and fiber-reinforced plastics composites and have made some tensile experiments in lengthways and transverse orientation with these composites. From the test, we have gotten the parameters on mechanical properties of composites. According to analyzing and comparing the experimental data and the geometry structures of these fabrics, we have tried to find the roles that the fabric structure played on tensile mechanical properties of warp knitted fabric reinforced composites. As a result, we find fabrics and composites tensile performance will decline with increasing the stitch density. By improving the weft density, fabric and composite tensile properties will be relatively stable. With the same weight of composite material, laminated fabric is less, and the tensile is lager. It helps manufacturer to control adjustment weft-insert and warp knitting parameters during the fabric knitting to enhance the fabric the quality.The multi-axial warp knitting fabric has the very big development space in the industry of compound materials. Our country will enlarge multi-axial warp knitting fabric application, therefore, the research of the principles and processes of multi-axial warp knitting machine and the discussion of the parameters of multi-axial weft-insert and warp knitting have the very important theoretical and practical significance.