Design And Fabrication Of Braided Composite Connectors

Fiber reinforced polymer composites have been widely used in aerospace,automobile,ship and other fields,and there are many preparation methods for fiber preform and composites.For the complex components,the combination of 3-D integral shaped braided technology and resin transfer molding technology is an ideal technical approach to achieve fiber through all parts of heteromorphic shaped composite components.Took the plate-tube orthogonal composite material connector as an example,based on the 2.5D woven with warp-stuffer structure and 3D 6-directional braiding structure,in the first forming direction bottom plate preform weaving process,according to the location and shape of the second forming direction branch tube preform size,design pulling out and adding in yarn weaving technology,set aside the second direction pipe preform braiding yarn required.In order to study the influence of near-net steering braiding technology on the first forming direction bottom plate.Firstly,based on the 2.5D woven with warp-stuffer structure,5 kinds of pulling out and adding in yarn structures in plate preform specimen were designed and prepared,Micro-CT was used to observe the morphological changes of the yarn cross-section and the distribution of yarn orientation in each system.The squeezed state of the pulled out and added in yarn changes along the thickness direction of the preform,and the cross-section shape of the pulled out and added in yarn are changed from an ellipse to a trapezoid,and then to a triangle.When the warp yarns are pulled out and added in,the cross-section of the weft yarns in contact with them change.The single-cell models of different pull-out and add-in yarn structures were established,and the volume of the unit cell fibers was calculated.It was found that the volume of the fibers increased by 1.2%-0.51%.Secondly,5 kinds of composites with pulling out-adding in yarns were tested by three-point bending in warp direction and shear resistance test.The results show that the retention rates of bending strength and modulus of the composites reach 82.6%-95.7% and 89.1%-97.9%,respectively.Samples tension crack surface surrounding the doffing and yarn,Composites appear local aggregation debonding during bending which with the structure of pulling out the new yarn after weaving one weft.Composites shear resistance test results show that composite shear strength retention rate reaches82.77%-86.68%.The yarns drawn and added at the fracture point of the sample were debonded with the interface of the matrix along the thickness direction,and some of the yarns that were not pulled out or added in were pulled apart and broken.Finally,the 2.5D woven-3D braided tube plate vertical intersection perform was designed and prepared based on the optimal scheme of binder warp be pulled out and added in once.Micro-CT was used to observe connector perform meso structure,it was found that the fibers continuously through the bottom plate and the branch pipe,especially at the junction of the plate and pipe,the yarn interweave structure is uniform and there is no penetrating hole,indicating that the integral shaped braided technology is reliable.