Reserch On Fabrication And Ablation Behavior Of Phenolic Impregnated Three-Dimention Carbon Fiber Braid Composites

The phenolic resin impregnated 3-D carbon fiber braid is a new heat protection composite material with lower density, lower heat conductivity and low mass ablation. It can be used as the widespread thermal protection system of the aerocraft in the high heat flux, high temperature and extreme condition. The PICA were prepared by the modified phenolic resin and carbon fiber weaves, using the ordinary pressure and vacuum impregnation technique. The feasibility of PICA preparation was testified by measuring the surface tension of phenolic resin and the wetting property between the phenolic resin and carbon fibre. Solidification process was formulated by the analysis results of DSC experiment of phenolic resin solidification. The thermogravimetric analysis of the solidification was taken from room temperature to 1100℃. The densities and percents of void of PICA were measured and the effect of impregnation technique and braid's densities were analsed ,which was on the densities and percents of void of PICA. The properties of compressive strength and ablation were evaluated, and the effect of braid's densities on it was analsed. The ablation property of PICA was evaluated by the oxyacetylene ablation experiment. The microstructure morphology of specimen before and after ablation was viewed by SEM.The experiments results indicates the surface tensions of the phenolic resin solution increase and contact angles between the resin and fiber decrease as the temperature grows. This proves the feasibility of the preparation. The mass loss of resin is small and the resin only release some solvent and small molecule substance ,in the temperatue range from room temperature to 550℃.And above 550℃, the phenolic resin oxidate and the mass loss of resin become large. The temperature 180℃is formulated as the peak temperature of resin solidification by the results of DSC.In the condition of same fiber braid, the impregnating time have no effect on the PICA's densities and percents of void. The densities increase and percents of void decrease after braid compact before impregnation, vacuum impregnation, vibration of ultrasonic waves. The carbon fiber braid densities have a large effect on it of PICA.As the braid densities grow, the densities of PICA increase. They are in the direct proportional relationship. The strain of specimens increases as the strength grows. The largest strength is 169.5MPa, appearing in the sample of C series. Mass ablation rate and linear ablation rate are small in the sample of B,C series. For the low densities samples of A and D series, their backside temperatures are higher than the ones of samples of B and C.