Research On Microstructure And High Temperature Mechanical Property Of 3D Fabric Reinforced C_f/Al Composites

3D reinforced C_f/Al composite are a typical lightweight, high strength and structure-properties can be designed composites. It not only has the advantages of the unidirectional reinforced C_f/Al composites with high specific strength and high specific modulus, small thermal expansion coefficient, good heat resistance and so on, and 3D woven structure makes it have good structural integrity and performance can be designed. 3D reinforced C_f/Al composites are a kind of advanced composite material which have great potential for development in the field of aerospace.In this paper, reinforcing materials were 3D five-directional woven M40 carbon fiber and matrix alloy was ZL301, 3D five-directional reinforced C_f/Al composites(3D-C_f/Al composite) were prepared by vacuum pressure infiltration. Firstly, the effect of fiber preheating temperature on microstructure and mechanical properties of3D-C_f/Al composites at room temperature and high temperature were studied. The optimum fiber preheating temperature was determined. On the basis of the above,tensile mechanical behavior of 3D-C_f/Al composites with two fiber volume fraction(50% and 45%) at room temperature and high temperature(200~300℃) was studied and the failure mechanism of 3D-C_f/Al composites at room temperature and high temperature tensile fracture was discussed. The main conclusions are as follows.The relative density and the uniformity of fiber distribution of 3D-C_f/Al composites prepared by vacuum pressure infiltration are improved with the increase of the fiber preheating temperature. However, the proportion of interfacial reaction products(Al4C3) of 3D-C_f/Al composites increased significantly with the increase of fiber preheating temperature, the microstructure uniformity of the composites prepared in the same fiber preheating temperature is good.The room temperature strength of 3D-C_f/Al composites increases firstly and then decreases with the increase of preheating temperature, the maximum strength(577MPa)of the composites is prepared by the preheating temperature of 570℃. The strength of the composites at high temperature(below 300℃) increases with the increase of the preheating temperature, the maximum strength of composite materials(549MPa) is prepared by the preheating temperature of 600℃. Interfacial bonding weakening caused by recovery of matrix alloy in the high temperature tension, which is advantageous to the interface slip and the fiber bearing function of the composite material, so as toimprove its high temperature mechanical properties.The difference of the microstructure uniformity and the density of 3D-C_f/Al composites prepared by 50% and 45% of the fiber volume fraction at the same preheat temperature(570℃) are not obvious, however, their tensile strength at room temperature are 577 MPa and 859 MPa respectively, so, increasing the volume fraction of fiber can improve the mechanical properties of the composites at room temperature and high temperature. Under the same condition of temperature and volume fraction of fiber,the tensile strength of 3D-C_f/Al composites increases first and then decreases with the increase of temperature, and the elastic modulus decreases with the increase of the temperature.The fracture limit strength of 3D-C_f/Al composites is higher than that at room temperature in high temperature tensile test. On the one hand, the interfacial bonding strength of the composites at room temperature is reduced by increasing the deformation temperature, which is conducive to exert the energy dissipation capacity of the external load by the interface slip. On the other hand, the residual stress caused by the fiber/matrix thermal expansion coefficient mismatch can be partially eliminated, so that the composites have a high temperature bearing capacity.