Meijie Yu

Study on the relationships of mechanical performance with the short-range and long-range structure of 500–900℃ carbonized fiber

The relationships of mechanical performance with the short-range and long-range structure of 500–900℃ carbonized fibers were studied by the combination of radial distribution function (RDF), Fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HRTEM), etc. In the range of 500–900℃, there were different laws of change for tensile strength and elastic modulus during different temperature stages. The tensile strength was more nearly directly proportional to temperature, especially at higher than 600℃. The elastic modulus increased slowly from 500 to 700℃, and then elastic modulus increased rapidly after 700℃. The short-range structures had no effects on the mechanical performance. The uniform increasing rate of tensile strength was closely related to the crystallinity degree and crystal size. The outstanding increase of orientation degree was closely related to the change of elastic modulus.

Densification treatment and properties of carbon fiber reinforced contact strip

Abstract The high temperature caused by current-carrying wear could affect the thermal reliability of resin-based contact strip greatly. This study adopted liquid-phase impregnation-carbonization (IC) technique to improve the thermal stability and densification of carbon fiber reinforced contact strip (CFRCS). The influence of this method was investigated by scanning electron microscopy, Fourier transform infrared spectrometry, thermal gravimetric analysis and energy-dispersive spectrometry; meanwhile, specimen composition and friction and mechanism properties were also analyzed. The results show that heat treatment is helpful in improving the material’s temperature tolerance. When specimens undergo IC treatment four times, resistivity and wear rate would reduce gradually under impregnating conditions of carbonization temperature (800°C), dipping liquid concentration (60%), and dipping temperature (60°C). IC treatment is effective in reducing material porosity and improving the impact resistance performance compared with only carbonized sample. Densification treatment can also improve the samples’ compressive strength and bending strength. The main wear mechanisms of CFRCS-25 and CFRCS-800 against copper with electrical current are similar; these are arc erosion wear and oxidation wear accompanied by adhesive wear. Adhesive wear and oxidative wear is more severe for CFRCS-25 than CFRCS-800.