Xinliang Wei

Threshold pressure and infiltration behavior of liquid metal into fibrous preform

A dynamic measuring apparatus was developed to investigate the infiltration process of liquid metal into the fibrous preform. 10% (volume fraction) chopped carbon fiber preforms were infiltrated with magnesium alloy under different infiltration pressures. The threshold pressure and flow behavior of liquid metal infiltrating into the preforms were calculated and measured. The microstructure of obtained Cf/Mg composites was observed. The results indicate that the measured threshold pressure for infiltration was 0.048 MPa, which was larger than the calculated value. The infiltration rate increased with the increase of infiltration pressure, but the increase amplitude decreased gradually. The tiny pores in the composites could be eliminated by increasing the infiltration pressure. When the infiltration pressure rose to 0.6 MPa, high quality Cf/Mg composite was obtained.

Influence of Notch on Mechanical Properties of Cf/Mg Composite Fabricated by LSEVI

Cf/Mg composite was fabricated by liquid-solid extrusion following vacuum infiltration technique and uniaxial tensile tests were conducted on the notched and unnotched specimens to investigate the mechanical properties of Cf/Mg composite. The effects of circular notch on the notched strength, net tensile strength, tensile modulus, and fracture strain of Cf/Mg composite were investigated. The notch sensitivity of Cf/Mg composite was elucidated through the notch strength ratio (NSR), fracture surface, and fracture mechanism. By comparing the experimental and theoretical NSR, the influences of notch size and stress concentration factor on notch sensitivity of Cf/Mg composite were investigated. The results showed that the fracture strain of the notched specimens increased with increasing the notch size. Meanwhile, net tensile strength, notched strength, and tensile moduli had opposite trends. The NSR had a functional relationship with the notch size and stress concentration factor caused by the notch had no influence on the NSR.

Effect of PyC coating on mechanical properties of Cf/AZ91D composites

ABSTRACT The microstructure of high strength PAN-based T700 carbon fibre (Cf) with pyrolytic carbon (PyC) coating was characterised. Effects of PyC coating on the surface of carbon fibres, interface characteristics, and mechanical properties of Cf/AZ91D composites were evaluated. The results showed that the carbon fibres with PyC coating had higher surface roughness and higher graphitisation which were beneficial to ease hazardous interface reaction. Cf-PyC/AZ91D composites with an optimal PyC coating that is about 150 nm thick and has low texture exhibited ultimate tensile strength of 416 MPa, which demonstrated 35% improvement compared with the Cf/AZ91D composites. The increase of mechanical properties of Cf-PyC/AZ91D composites could be ascribed to a synergistic effect of the rough Cf surface interlocking, an optimum interfacial bonding between fibres and matrix, and protection of fibres from a corrosive attack of the aluminium element in the matrix.

Effect of fabrication parameters on carbon fibre reinforced magnesium matrix composite components

Carbon fibre reinforced magnesium matrix (Cf/Mg) composite components were made by liquid–solid extrusion process following vacuum infiltration technique. The effect of varying fabrication parameters (extrusion temperature, infiltration pressure and filling pressure) on the forming quality of Cf/Mg components was investigated. The experimental results showed that the extrusion temperature and the infiltration pressure played important roles, and the filling pressure played a secondary role. The components can be obtained at an extrusion temperature of 590°C, an infiltration pressure of 20 MPa and a filling pressure of 0.2 MPa. The ultimate tensile strength of the Cf/Mg composite components was 290 MPa, which was increased by 81% compared with that of casting AZ91D.

Effect of holding pressure on densification and mechanical properties of Cf/Mg composites

Carbon fibre reinforced magnesium alloy matrix composites were fabricated by using liquid–solid extrusion directly following vacuum infiltration technique. The experimental results showed that the microstructures of Cf/Mg composites depended on the holding pressure. The porosity was reduced gradually, and the densification was improved obviously, respectively, with the increase of the holding pressure. The densification, hardness and Ultimate tensile strength of Cf/Mg composites were significantly improved as the holding pressure increased in the range of 0.1–15 MPa. The densification was not obvious, but the UTS of the Cf/Mg composites decreased gradually as the holding pressure increased in the range of 25–45 MPa. The Cf/Mg composites presented a good performance when the holding pressure was about 15 MPa.