Abstract
Layer-structured interphase, existing between reinforcing fiber and ceramics matrix, is an indispensable constituent for fiber-reinforced ceramic composites due to its determinant role in the mechanical behavior of the composites. However, the interphase may suffer high residual stress because of the mismatch of thermal expansion coefficients in the constituents, and this can exert significant influence on the mechanical behavior of the composites. Here, the residual stress in the boron nitride (BN) interphase of continuous SiC fiber-reinforced SiC composites was measured using a micro-Raman spectrometer. The effects of the residual stress on the mechanical behavior of the composites were investigated by correlating the residual stress with the mechanical properties of the composites. The results indicate that the residual stress increases from 26.5 to 82.6 MPa in tension as the fabrication temperature of the composites rises from 1500 to 1650 °C. Moreover, the increasing tensile residual stress leads to significant variation of tensile strain, tensile strength, and fiber/matrix debonding mode of the composites. The sublayer slipping of the interphase caused by the residual stress should be responsible for the transformation of the mechanical behavior. This work can offer important guidance for residual stress adjustment in fiber-reinforced ceramic composites.
Highlights
IntroductionJ Adv Ceram 2021, 10(5): 0–0 fracture [3,4]. These favorable mechanical characteristics combined with other advantages, such as low density and high temperature corrosion/oxidation stability, enable aero-engines to operate with increasing efficiency and reducing emissions [5]
Continuous fiber-reinforced ceramic matrix composites (CFCMCs) are promising materials for replacing some nickel-base super-alloys in hot section components of advanced aero-engines [1,2]
For multiple-phase ceramic composites fabricated at high temperatures, residual stress in the constituents evolves due to the mismatch of thermal expansion
Summary
J Adv Ceram 2021, 10(5): 0–0 fracture [3,4]. These favorable mechanical characteristics combined with other advantages, such as low density and high temperature corrosion/oxidation stability, enable aero-engines to operate with increasing efficiency and reducing emissions [5]. SiCf/SiC (continuous SiC fiber-reinforced SiC matrix composites) is one of the most widely studied CFCMCs and residual stress in the composites has received increasing attention recently. Research has shown that SiCf/SiC prepared by silicon melt infiltration exhibits residual tensile stress as high as ~1.45 and 0.5–0.7 GPa in the matrix and the fiber, respectively [23]. Recently there is growing research investigating the residual stress in SiCf/SiC, to the best knowledge of the authors, the interfacial residual stress of the composites and its effects on the mechanical behavior have not been studied. The interfacial residual stress of SiCf/SiC composites prepared by nano-infiltration and transient eutectic-phase (NITE) method was investigated using a micro-Raman spectrometer.
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