Research On Characteristics Of Microstructure And Mechanical Properties Of Laminated Puncture Structural C_f/Al Composites

In addition to its high specific strength,high specific modulus,excellent impact resistance and corrosion resistance,the most important features of 3D braided C_f/Al composites are its light weight,low density,designable structure and function,and the ability to weave complex special-shaped parts.It has broad application foregrounds in aerospace,weaponry and other fields,and especially show great advantages in the development of aero-engines.In this paper,M40J fiber was used to weave a laminated puncture structural preform,and ZL301 alloy was used as the matrix material,Laminated puncture structural C_f/Al composites with 47.5%fiber volume fraction were fabricated by vacuum pressure infiltration.The characteristics of microstructure,bending and shear properties of the composites at room temperature and high temperature was mainly studied,The influence of the test temperature on the bending and shear properties of the composites were analyzed,and the bending and shear property failure mechanism were further analyzed.It can provide theoretical support for the practical engineering application of laminated puncture structural C_f/Al composites and promote the wider engineering application of 3D braided carbon fiber reinforced metal matrix composites.The research results indicate that the density of laminated puncture structural C_f/Al composites are 96.3%.There are a certain degree of fiber segregation in the warp and weft microstructure of the composites,and there are more micvoids defects in the weft microstructure than in the warp microstructure.The residual stress makes the morphology of the fiber filaments in the composites show pea shape.The composites are mainly composed of C,Al,Al₃Mg₂and Al₄C₃phases,The interface outline between the carbon fiber and the matrix alloy is clearly,and the interface is well combined.The lattice constant of Al in composites matrix alloy is 0.40845nm,it is larger than the lattice constant of 0.40785nm of Al in ZL301 alloy.which is mainly caused by the residual stress causing the matrix phase to be further pulled.the diameter and tensile strength of the original fiber filaments are 5.73?m and 4400MPa,respectively.While the diameter and tensile strength of the extracted fiber filaments are 5.24?m and3251.8MPa,respectively.the morphology of the extracted fiber filaments in composites has longer and deeper scratches than the original fiber filaments,and there is a layer of adhesion on the surface.It is caused by the interface reaction between carbon fiber and molten aluminum during the high temperature infiltration of the composites.The bending test results indicate that as the test temperature increases,the bending properties of laminated puncture structural C_f/Al composites shows a descend trend.Among them,the bending strength of the composites at room temperature,350?and400?are 310.2MPa,175.2MPa and 160.8MPa,respectively.The bending strength of the composites at 350?and 400?are 43.5%and 48.2%lower than those at room temperature.The bending modulus of the composites at room temperature,350?and400?are 101.4GPa,90.1GPa and 87.5GPa,respectively.The bending modulus of the composites at 350?and 400?are 11.1%and 13.7%lower than those at room temperature.The bending failure mechanism of the composites are that the compression of the inner side,and the surface damage of the composites are mainly the clusters of the matrix alloy.The degree of buckling deformation of warp fiber bundles and the extrusion deformation of weft fiber bundles are becoming more and more serious with the increase of the test temperature.However,the composites were damaged by tensile at the outer side,which resulted in the matrix cracking,and the matrix alloy cracking slightly improved with the increase of the test temperature,accompanied by the phenomenon of fibers are pulling out.The results of the shear test indicate that as the test temperature increases,the shear properties of laminated puncture structural C_f/Al composites show a descend trend.Among them,the shear strength of the composites are 78.6MPa at room temperature,and the shear strength of the composites are 46.0MPa at 350?,which are 41.5%lower than at room temperature.The shear modulus of the composites are 8.26GPa at room temperature,and the shear modulus of the composites are 1.85GPa at 350?,which are77.6%lower than at room temperature.The shear failure mechanism of the composites are that the shear failure first occurs at the damage at the interface between the“V”-shaped carbon fibers and the matrix alloy,and the crack expands about 45°along the direction of the shear force.With the test temperature increases,the buckling deformation of warp fiber bundles,the extrusion deformation of weft fiber bundles and the deflection of Z-direction puncture fiber bundles are becoming more and more serious.Among them,the damage on the surface of the composites are mainly manifested in cracking and wrinkling of the matrix alloy.