热压烧结C_f/SiC复合材料的力学性能

MECHANICAL PROPERTIES OF HOT_PRESSED CARBON FIBER REINFORCED SILICON CARBIDE COMPOSITES

以ＡｌＮ－ Ｙ２Ｏ３ 为烧结助剂体系，采用先驱体转化－ 热压法制备出了Ｃｆ／ＳｉＣ复合材料． 研究了烧结助剂及其用量和烧结温度对复合材料力学性能的影响． 结果表明，由于ＡｌＮ－ ＳｉＣ的固溶和液相烧结的作用，复合材料具有较好的力学性能． 烧结温度为１ ８００ ℃时，复合材料的抗弯强度和断裂韧性随烧结助剂用量的增加而不断提高；烧结温度为１ ８５０ ℃时，烧结助剂用量较少的复合材料具有很好的断裂韧性． 随着烧结助剂用量的增加，虽然复合材料的抗弯强度不断提高，但由于晶界相和ＡｌＮ－ ＳｉＣ 固溶体量的增加，使纤维与基体的结合过强，从而导致纤维不能发挥拔出作用，复合材料的断裂韧性值降低． 不过，复合材料由于纤维的脱粘仍具有较好的断裂韧性． 碳纤维的脱粘和拔出对Ｃｆ／ＳｉＣ 复合材料的增韧起到了重要的作用．

C f/SiC composites were prepared by precursor conversion/hot_pressing with AlN-Y 2O 3 as additives. The effect of additives (AlN and Y 2O 3) and sintering temperature on the mechanical properties of the composites were investigated. The results show that, owing to the formation of AlN-SiC solid solution and liquid phase sintering, the composites exhibit better mechanical properties. The mechanical properties will be improved with the content of sintering additives at lower temperature(1 800 ℃). At higher temperature (1 850 ℃), the composites with less additives show excellent fracture toughness. With the increase of the additives, the flexural strength will be improved, but fracture toughness will decrease as the result of the strengthening of the interface between carbon fiber and matrix due to increase of grain boundary phase, which causes the failure of the pullout of fibers. On the other hand, the composite displays better fracture toughness because of the debonding of fibers. Debonding and pullout of the fibers play an important role in the toughening of these composites.