SiC_(f)/SiC复合材料的水淬失效行为及模拟分析

Water quenching failure behavior of SiC_(f)/SiC composites andsimulation analysis

采用先驱体浸渍裂解(PIP)工艺制备了不同尺寸的SiC_(f)/SiC复合材料,对复合材料的物理性能及水淬性能进行研究,并通过ABAQUS有限元模拟对水淬过程进行分析。结果表明,正交铺层的SiC_(f)/SiC复合材料的弯曲强度为553 MPa,层间拉伸强度为19.2 MPa。采用该复合材料进行水淬实验时,3次循环后出现明显裂纹,随着水淬次数的增加,裂纹发生扩展。样品尺寸增加时,S8和S12在水淬过程中均出现纵向基体裂纹,其中S12样品一端的5/6层出现沿纤维0°方向开裂的现象,因此S12在水淬过程中表现出更为复杂的开裂模式。通过有限元分析发现,水淬过程中,S4和S8样品6/7层裂纹出现了先开裂后闭合的趋势,这可能是该样品中主裂纹扩展“挤占”次裂纹空间所致。通过对样品在水淬过程中的应力计算,发现样品尺寸增大时,由于温度梯度引起的热应力增加,S8和S12样中的应力接近40 MPa,因此出现了基体开裂现象。

As one of the key performance indicators of composites,thermal shock performance may be related to sample size.In order to explore the thermal shock performance of SiC_(f)/SiC composites,high temperature water quenching experiments at 1,200℃were conducted with SiC_(f)/SiC rectangle composite samples prepared by polymer infiltration pyrolysis(PIP)process.In addition,the above water quenching experiments were simulated by ABAQUS finite element software.In this study,three samples(i.e.,S4,S8,S12)from SiC_(f)/SiC composites with bending strength and interlaminar tensile strength of 553 MPa and 19.2 MPa,respectively were taken as the subjects of water quenching experiments.During the water quenching experiments,the samples started to form microcracks after 3 cycles,which expanded with the increase of the number of cycles.After 8 cycles,matrix cracks started to appear in S8 and S12 while a crack was observed extending along the 0°fiber direction in 5/6 layer at one end of S12.According to the finite element analysis results,the cracks in the 6/7 layers of S4 and S8 were firstly cracked and then closed,which might be due to space occupation of the secondary cracks caused by main cracks's propagation.The outcomes of stress calculation demonstrated that the thermal stress of the samples in this study increased with the increase of sample size due to the temperature gradient.The thermal stresses in S8 and S12 reached 40 MPa,resulting matrix cracks and extension.