热解碳含量对碳/碳-聚酰亚胺复合材料性能的影响

Effect of pyrolytic carbon content on properties of carbon/carbon-polyimide composites

通过化学气相渗透和浸渍-固化成型工艺制备碳/碳-聚酰亚胺复合材料。首先采用化学气相渗透法对碳毡进行热解碳的沉积,制得热解碳含量分别在7.33%(质量分数,下同),14.55%,22.00%的多孔碳/碳坯体,再经过特定的浸渍-固化工艺,依次制得碳/碳-聚酰亚胺复合材料P1,P2,P3以及未添加热解碳的对照组P0。通过SEM、线膨胀系数测试和力学性能测试,探究不同热解碳含量对碳/碳-聚酰亚胺复合材料微观形貌结构、平均线膨胀系数以及力学性能的影响。结果表明:在20~300℃的温度区间,P0,P1,P2,P3的XY向平均线膨胀系数在(0.67~0.79)×10^(-6)℃^(-1)之间,四组XY向平均线膨胀系数基本相当。P1,P2,P3的Z向平均线膨胀系数较P0依次降低41.6%,41.8%,24.1%,热解碳显著降低了材料的Z向平均线膨胀系数。P0,P1,P2,P3的XY向压缩强度依次是243.91,244.73,216.65,210.79 MPa,Z向压缩强度依次是269.22,258.80,246.68,219.20 MPa,P1压缩强度与P0相当。P0,P1,P2,P3的Z向弯曲强度依次是92.77,77.11,80.71,86.06 MPa。不同的热解碳含量对材料的力学性能影响不同,较低的热解碳含量基本保持了材料的压缩强度,而较高的热解碳含量可基本保持材料的弯曲强度。

Carbon/carbon-polyimide composites were prepared by chemical vapor infiltration and vacuum-pressure impregnation curing process.Firstly,the carbon felt was deposited with pyrolytic carbon by chemical vapor infiltration method to prepare porous carbon/carbon materials with pyrolytic carbon contents of 7.33%(mass fraction,the same below),14.55% and 22.00%,respectively.Then,through a specific impregnation curing process,the carbon/carbon-polyimide composites P1,P2 and P3 and the control group P0 without pyrolytic carbon were obtained in turn.Through SEM,linear expansion coefficient test and mechanical properties test,the effects of different pyrolytic carbon contents on the microstructure,average linear expansion coefficient and mechanical properties of carbon/carbon-polyimide composites were investigated.The results show that in the temperature range of 20-300℃,the XY-direction average linear expansion coefficients of P0,P1,P2 and P3 are between(0.67-0.79)×10^(-6)℃^(-1),and the XY-direction average linear expansion coefficients of four groups are basically the same.The Z-direction average linear expansion coefficients of P1,P2 and P3 decrease by 41.6%,41.8% and 24.1%,respectively compared with P0.Pyrolytic carbon significantly reduces the Z-direction average linear expansion coefficient of materials.The XY-direction compressive strengths of P0,P1,P2 and P3 are 243.91,244.73,216.65 MPa and 210.79 MPa,respectively,and the Z-direction compressive strengths are 269.22,258.80,246.68 MPa and 219.20 MPa,respectively.The compressive strength of P1 is equivalent to that of P0.The Z-direction bending strengths of P0,P1,P2 and P3 are 92.77,77.11,80.71 MPa and 86.06 MPa,respectively.Different pyrolytic carbon contents have different effects on the mechanical properties of materials.The lower pyrolytic carbon content can basically maintain compressive strength of materials,while the higher pyrolytic carbon content can basically maintain bending strength of materials.