The Geometric Model Of Multi-axial Warp-knitted Composite Performs

With the development of science and technology as well as new materials, textile materials are emerging one after another. Because of its excellent mechanical properties and simple process, the multi-axial warp-knitted composite perform has become a kind of perfect reinforced material. And its products have been widely used in the fields of aerospace, wind power blades, transportation, construction and so on, which has a great development potential. As the extensive use of multi-axial warp knitted composites, the in-depth study of its perform microstructure is particularly important. However, the study at home and abroad was mostly based on the multi-axial warp knitting technology at that time, which couldn't make a true reflection of the geometric structure of modern multi-axial warp knitting composite perform with chopped fibers. As a result, it failed to guide the design and production of multi-axial warp-knitted reinforced materials. Therefore, the main purpose of this paper is to establish an appropriate 3D structure model of the novel multi-axial warp-knitted composite perform with chopped fibers by the further research on the structure of modern multi-axial warp knitting composite perform, and then a CAD system to achieve three-dimensional simulation of the perform model was developed. Meanwhile, according to the model, its fiber volume fraction formula was derived, and the theoretical and experimental values were compared to verify the correctness of the model.Firstly, based on the study of production equipment, materials and knitting principle, the structure of the multi-axial warp knitting composite perform was analyzed, and also the excellent performance together with its wide range applications were researched.Subsequently, with the reasonable hypothesis, the 3D solid model of the loop yarns, the insertion yarns and the chopped fibers were developed with NURBS curves and surfaces. And then the 3D computer simulation system of multi-axial warp knitting composite perform was developed with VC++.NET and OpenGL, which could simulate the perform.At last, According to the model, the unit cell of the perform was selected based on the analysis of its microstructure. With the relation between geometric parameters and process variables analyzed, the theoretical fiber volume fraction formula of the perform was given out. Furthermore, Using different specifications of perform as the samples, the theoretical value of fiber volume fraction was calculated efficiently by CAD system. Comparing the theoretical value with the experimental value, it indicated that the fiber volume fraction of the perform was in good agreement between theoretical and experimental value, which means that the model was practical. Meanwhile, the factors leading to the deviations between theoretical value and experimental value were analyzed, they were mainly attributed to the ideal assumption of the perform, the resin-rich zones in the composites after the molding process and so on.Form this research, the permeability and flow conductivity of the perform can be predicted, and also the design together with its product development cycle can be improved.