Tensile Properties of Continuous SiCf/TC17 Composites at Room Temperature
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 1 960 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 1 870 MPa to 1 797 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.
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