Design Of A Carbon/carbon Crucible Preform Needling Machine Based On The Knitting And Felting Process

Carbon/carbon composites are a new type of engineering material with excellent resistance to high temperatures and corrosion and are now widely used in various fields such as aviation and the military.As one of the main production methods for carbon/carbon composite materials,the needle-punching technology is used to form a quasi-3D mesh structure with sufficient strength and toughness between the layers of the preform,which enhances the shear strength and connection properties between the carbon cloth/mesh layers and has good development prospects.However,in China,the prefabricated crucible body is mainly formed using a stabbing process and a stitching process.The stabbing process is carried out manually by laying the carbon fabric layer,which requires manual cutting of the carbon fabric in the bottom part of the crucible due to the cylindrical shape of the crucible,the curved surface at the junction and the nearly flat structure at the bottom.Both processes affect the performance of the finished crucible to a certain extent.To address this problem,this paper designs a needle punching machine for carbon/carbon crucible preforms based on the braiding process,weaving the carbon cloth with multifilament braiding technology and using the braiding closure technology to effectively ensure the thickness of the crucible bottom,effectively improving the quality of the crucible preform layering and finally realising the needle punching of the crucible preform:The design requirements of the needle punching machine for carbon/carbon crucible preforms and the process flow are clarified,on the basis of which the design of the key components of the needle punching machine is proposed.For the lightweight requirements of the needle punching mechanism,cylinder needling is used;the rotation of the needle punching platform is realised using a slewing support;the needle plate is reasonably designed based on the principle of profiling design;the rest of the key components are designed in detail as well as the hydrostatic analysis to meet the design index requirements.The overall design of the needle punching machine for carbon/carbon crucible preforms is obtained by combining the solutions and designs of the various components,and a three-dimensional model of the complete assembly of the needle punching machine is created based on Solidworks software.The contact problem analysis is carried out for the slewing bearing parts of the needling machine.In order to ensure the normal operation of the needling machine,the slewing bearing components are reasonably selected and Workbench software is used to carry out a finite element contact analysis on the whole to obtain the stress distribution of the rolling body.Based on the above results the local model is simplified and based on the Hertzian contact theory mathematical model calculation and Ansys finite element analysis of the local rolling body and the maximum contact stress of the raceway in two ways,and the error analysis of the two results,the maximum contact stress obtained in line with its allowable contact stress requirements.In order to ensure that the surface quality of the preformed body meets the process requirements,the needle plate of the needling machine is designed based on three needle laying methods: herringbone needle laying,first row staggered needle laying and bidirectional staggered needle laying.Based on the coordinate projection theorem and the rotating coordinate algorithm,the stitch simulation programme is designed and the interface is developed in Visual Studio software.On this basis,stitch simulation experiments with different step sizes are carried out for the three needle laying methods.The 32" charcoal/charcoal preform needling machine is assembled in the field and the needling function is verified as well as the uniformity of the stitches.