连续SiCf/TC17复合材料室温偏轴拉伸性能研究

Tensile Properties of Continuous SiCf/TC17 Composites at Room Temperature

采用磁控溅射法结合热等静压工艺制备SiCf/TC17复合材料,通过SEM观察试样的断口形貌,研究了复合材料在室温的偏轴拉伸性能及断裂机制。结果表明:纤维偏轴角度在0°~2°间,复合材料轴向性能变化较小,拉伸强度稳定在1960~1987 MPa;纤维偏轴角度再增大时(>2°),材料拉伸强度近似呈单调线性降低,由1870 MPa降至1797 MPa。纤维偏轴角度较小时(≤2°),平坦区基体与纤维断裂面平整,且两者的断裂面平行。纤维/基体界面没有明显的脱粘破碎迹象;纤维偏轴角度较大时(>2°),部分纤维存在“斜切断裂”,纤维拔出距离变长,且不再与基体的断裂面保持在同一平面,基体撕裂损伤严重。依据断口形貌结合局部承载模型,详细论述了SiCf/TC17复合材料两种拉伸失效的断裂过程。纤维偏轴角度较小时(≤2°),裂纹萌生于纤维间距较小的反应层,在界面处钝化或偏转进而形成不同截面的平坦区,当纤维超过承载能力极限,试样整体断裂;纤维偏轴角度较大时(>2°),“拉-剪”耦合效应导致C涂层与反应层间的界面脱粘破碎形成裂纹源,裂纹加速反应层受损或导致界面脱粘致使纤维断裂,当基体及剩余纤维超过承载能力极限,试样整体断裂。

SiCf/TC17 composites were prepared by magnetron sputtering and hot isostatic pressing.The off-axial tensile properties and fracture mechanism of SiCf/TC17 composites at room temperature were studied by observing the fracture morphology of samples by SEM.The results show that the axial properties of the composites change little when the axial deflection Angle of the fibers is between 0°and 2°,and the tensile strength is stable in the range of 1960 to 1987 MPa.When the off-axis Angle of the fiber is increased(>2°),the tensile strength of the material is approximately monotonically linear,decreasing from 1870 MPa to 1797 MPa.When the fiber off-axis Angle is small(≤2°),the matrix and the fiber fracture plane in the flat region are flat,and the fracture plane of them is parallel.There is no obvious sign of desticking and breaking at the fiber/matrix interface.When the fiber off-axis Angle is larger(>2°),some fibers have"oblique fracture",the fiber pulling distance becomes longer,and the fiber is no longer in the same plane as the fracture plane of the matrix,and the matrix is seriously torn and damaged.Based on fracture morphology and local load model,two kinds of tensile failure fracture processes of SiCf/TC17 composites were discussed in detail.When the fiber off-axis Angle is small(≤2°),the crack initiation occurs in the reaction layer with small fiber spacing,and then passivates or deflections at the interface to form a flat area with different cross sections.When the fiber exceeds the limit of bearing capacity,the sample breaks as a whole.When the fiber off-axis Angle is large(>2°),the"tension-shear"coupling effect leads to the interfacial debonding break between the C coating and the reaction layer to form a crack source,and the crack accelerates the reaction layer to be damaged or leads to interfacial debonding resulting in fiber fracture.When the matrix and the remaining fiber exceed the limit of bearing capacity,the specimen breaks as a whole.