Trimming On The Mechanical Properties Of 3d Textile Composites

Three dimensional braiding composites is a new material. The integrated fiber network provides stiffness and strength in the thickness direction, thus no the inter-laminar failure, which often occurs in conventional laminated composites. The mechanical properties of integrated three dimensional braiding composites are very good, so the areas of aviation and space pay attention to it.Sometimes the fiber and the integrated fiber network in the three dimensional braiding composites will be damaged since its working environment is often very abominable and the surface is cut and ablated inevitably. In the other hand, some composites have to be cut in order to meet the final need. The effect on the mechanical properties of the damage must be noticed in the design. The paper studied the effect of cut-edge on mechanical properties of three-dimensional braiding composites by comparing the cut-edge and uncut-edge composites. The study will provide the theoretic base for the design and application of three dimensional braiding composites.In this paper, the three dimensional braiding composites are cut by four ways, the strength and modulus of tensile, compress and bending properties of the cut-edge and uncut-edge is studied. Then the unit cells model of the cut-edge with uncut-edge composites were compared. And the formula of the length of the cut braiding yarn in the composites was derived.The results show that the strength and modulus of tensile, compress and bending properties of the three dimensional braiding composites will decrease with the braiding angles increasing, which also suit the cut-edge composites. When the composites is cut along the width, the strength and modulus of tensile and bending properties and the strength of the compress are not changed, but the modulus of compress was reduced by about 20%. The strength and modulus of tensile, compress and bending properties were reduced by approximately 60% when the composites is cut along the thickness and the width. The results show that when the width of three dimensional braiding composites is very large, the mechanical properties of the composites are not affected by the cut-edge. The analyzing for the microstructures of 3-D braiding cut-edge and uncut-edge composites shows that the mechanical properties of 3-D braiding cut-edge composites have a strong relation with the remained length of cut yarn in it. For example, the mechanical properties of the composites two-edge-cut along the width have no notable change, since the remained length of cut yarn in it is 42-68mm. On the other hand, the mechanical properties of the composites single-edge-cut along the thickness have great decrease, since the remained length of cut yarn in it is 11-19mm. The reason of the different remained length of cut yarn in the composites is that the thickness and the width of samples are different. It shows that the mechanical properties of the composites cut-edge along the width or the thickness have no notable change when the width or the thickness reaches a certain degree. This will be a great benefit to the design and the decrease of the cost of making the composites.