Research On Process Of Three-Dimensional Woven Farbic In Multi-Rapier Loom

As a preform of3D woven composites,3D woven fabrics possess a yarn distribution in plane, as well as in thickness direction, forming an spacial reticulate structure, resulting in significant improvement of interlaminar properties and damage tolerance, while maintaining the advantages of high specific rigidity and strength, etc. Because of overall formability and designability,3D woven fabrics in different size and shape can be one-time formed with3D weaving technology.Multi-rapier loom, a new type of loom designed and manufactured based on common rapier loom, can weave complex multilayer3D fabrics. But a special research system of multi-rapier loom has not formed at present. The multi-rapier loom developed jointly by Textile Institute and Machinery Institute of Donghua University, integrated a number of new process, is much maturer in technology. The weaving method of3D woven fabrics in the loom, including looming draft design and weaving process, was studied deeply and systematically in this paper.Looming draft design of multi-eye heddle weaving was designed. As for different3D woven fabrics, two different methods are intruduced:(1) binding analysis method:based on traditional weaving technology, analysis the stitching way of fabrics, lift heald frame to form cross sheds, thus warp yarns from different heddle eye layers binding and eventually forming the whole fabric;(2) holistic method:consider interweaving in its entirety, try different ways of shedding and weft insertating to find the right shedding and weft-insertion, and conclude the lifting plan and weft-insertiting plan at last.Binding analysis method is suitable for nonpenerative fabrics, while holistic method is a way of exploratory analysis, suitable for all fabrics. Though different from each other, there still are internal relations between the two methods.Weaving process of multi-rapier loom is similar with traditional looms. Threading of multi-eye heddle should be done one by one. And attention should be payed on weft encryption during lifting plan and weft-inserting plan setting. In order to make sheds more clear and warp tension more uniform, it is suggested that front rest should be set in the middle of all weft-inserting sheds, and that back rest should be replaced by a hierarchical positioning device. Through mathematical calculation, the optimum horizontal height and horizontal distance are determined. Results show that with the increasing of horizontal distance, the height of each hierarchical channel increases, and the warp tension difference decreases. As a prototype of multi-rapier loom, there are unreasonable parts needing to be improved. To make the weft gripper wor, a metal spring leaf was added to increase the positive pressure of gripper area. After analyzing the selvage problem, it is pointed that changing rapier head to a device carrying shuttle is the optiomal solution.Finally, three fabrics are made sucessfully. They are loose orthogonal angle-interlock, layer-to-layer inclined angle-interlock and multi-layer weft stitched fabric. And the preliminary analysis shows:(1) cross-sectional structures of the three fabrics are as uniform as a whole, no obvious stitching trace between junction layers caused by heald eyes;(2) sliced sectional images show that there is a big difference between the actual structure and the design of fabric;(3) with the current thread count, internal yarns of fabric fail to stack as required, indicating that some potential problems exist, and that technology and mechanism need to be improved in subsequent study.In the end of the paper, a model based on real-sectional structure of the fabric was built and a preliminary calculation of the theoretical thickness was carried out.