Study On The Integrated Performance Of Carbon Fiber Composites Based On Different Three-Dimensional Woven Structures

With the increasing use of advanced resin matrix composite materials in the aviation field,carbon fiber composite material,as a kind of advanced resin matrix composite materials,has become one of the most popular research directions.The traditional 2D laminate carbon fiber composites perform excellent in-plane mechanical properties,but their Z-directional properties are relatively low,and are easy to be delaminated and damaged after low velocity impact.Additionally,the artificial laminating is inefficient and high-cost.Therefore,researchers start to pay attention to the three-dimensional(3D)textile structural reinforcement,especially for forming complex shaped composites.However,most researches focused on structure design of 3D perform and the comparison of in-plane mechanical properties of composites with varied structures.Few studies were carried out in the field of the integrated mechanical properties of 3D textile structural composites and the relationships with woven structures.In this research,three different 3D woven structures,Shallow-Straight-Joint,Shallow-BendJoint and 3D Orthogonal,were selected as basic structures of these performs.All these performs were woven with carbon fibers and prepared to be composite samples.Integrated mechanical properties were tested and compared among the three structures,providing a reference for structural design and applications of the 3D woven composites.Firstly,the 3D performs were woven with T800 carbon fibers on a rapier weaving loom.The fabric surface were observed with a 400 X USB microscope,and simply analyzed.The results indicated that: there were some broken filaments on the fabrics' surface because of interweaving.Among the three structures,the surface of fabrics with Shallow-Bend-Joint structure was the worst while the Shallow-Straight-Joint structure had the best surface performance.Additionally,in the composite preparation process,the Vacuum assisted resin infusion(VARI)technology was applied.In order to ensure the preparation of 3D carbon composites successfully,some technical parameters,such as shape and size of the distribution medium,were modified.All samples in the mechanical tests were cut based on the ASTM test standards,and were tested in terms of tensile property,bending property,compression property and short-beam-shear in three directions of XYZ.With comparing the different integrated performances,some conclusions were conducted as follows: 3D orthogonal structural reinforcement preform had the highest contribution to the composite mechanical properties,because its warp yearns were straightly maintained in the structure.Composites with the Shallow-Straight-Joint structure had the best surface properties and relatively balanced mechanical properties,so it could be the best choice for 3D woven composites structural design.Owing to the frequently interlocking,composites with Shallow-Bend-Joint structures achieved the best anti-delamination property but with the worst surface performance.Meanwhile,the other mechanical properties of composites with Shallow-Bend-Joint structures were bad,leading to the worst integrated performance among the three structures.At last,to compare the integrated properties of the three different structures,weighting factors in three directions(XYZ)were identified based on requirements of a specified component.The unitary compressions of three different structural composites were calculated and simulated with the weighting factors.This method could be applied to evaluate the composites' integrated performance in multiple directions and to offer some references for selecting 3D woven composite reinforcement structures.