Development Of 3D Woven Fabric With Gradual Thickness Change

A tough stage of independent study on large aircraft was encountered by our country at present, how to significantly reduce weight of the engine and ensure its strength need be considered deeply. Applying the high performance composite fan blade into components of aircrafts’ engine was a core idea. Therefore, there’s a certain importance implied in this study on the high performance composite fan blade preform. The fan blade preform used in the aircrafts’ engine isn’t a flat plate whose thickness is uniform but a plate whose sectional thickness is changeable in both length and w idth direction. The three-dimensional woven fabric with continuously variable thickness in longitudinal direction was designed as the preform of fan blade by existing studies, and the second-generation mult i-eye heddle and mult i-rapier loom modif ied on the basis of the first-generation loom was selected as the woven equipment by which the variat ion of the thickness has been accomplished, but according to actual shape of the fan blade unfolded to a long plate shape whose thickness is variable in bi-direction, the preform was hard to form net-shapely. The fabric whose thickness is variable in bi-direction was woven in this paper with the second-generation mult i-eye heddle and mult i-rapier loom on the fundament of the existing researches.Firstly, the structural design of the three-dimensional woven fabric with variable thickness in length and width direction based on the variable thickness structure were implemented in this paper. Reasonable distribution scheme of warp-wise inlay was the basis of the structural design, as well design method starting from the middle part of a fabric combine with the special threading method of warp-wise inlay was designed according to the distribution of warp-wise inlay and design principles were used in the internal structure of the fabric, the target structure meeting the design requirements was finally achieved.Then, problems encountered during the woven process were analysed and suggestions improving the loom were put forward through weaving the target s tructure with the second-generation multi-rapier loom. Woven difficulties laying in the woven process of three-dimensional woven fabric with variable thickness in bi-directional which is more complicate than the variable thickness in length direction were solved by applying the method of increasing the number of heald frames. As the number of heald is increased, the weft-insertion problems caused by reduction of the shed’s height behind the loom were handled by applying multi-eye heddle of different specifications in order to achieve gradually inclining distribut ion of the heddle eye. The problems of Low efficiency, tension unstability and formation defects on edge caused by weft-insertion with hands were solved by applying mult i-box weft-insertion machinery to achieve the constantly weft-insertion. The short circuit on the mult i-rapier loom caused by the carbon fibers can be solved with an installat ion of explosion-proof devices using positive pressure in the woven process.Then, the condition of the loom and the stability in the woven process were debugged by weaving the ordinary three-dimensional woven fabric whose shape is flat plate. Finally, the bi-directional three dimensional woven fabric was woven on the debugged multi-rapier loom, its full woven process and the off-loom fabric were analyzed in this paper.The thicknesses of each section in both length and width direction were examined after the off-loom fabric’s structure was stable. Results from analysis of available data: The variable thickness structure was the basis of the structural design of variable thickness in bi-direction. And the target structure could be achieved by the reasonable distribut ion scheme of warp-wise inlay combine with the special threading method of warp-wise inlay. However, the lack of changing range in the width direction was the primary problem when study in a deep going way.