Comparisons of Damage Evolution between 2D C/SiC and SiC/SiC Ceramic-Matrix Composites under Tension-Tension Cyclic Fatigue Loading at Room and Elevated Temperatures.

Longbiao Li

doi:10.3390/ma9100844

Abstract

In this paper, comparisons of damage evolution between 2D C/SiC and SiC/SiC ceramic-matrix composites (CMCs) under tension–tension cyclic fatigue loading at room and elevated temperatures have been investigated. Fatigue hysteresis loops models considering multiple matrix cracking modes in 2D CMCs have been developed based on the damage mechanism of fiber sliding relative to the matrix in the interface debonded region. The relationships between the fatigue hysteresis loops, fatigue hysteresis dissipated energy, fatigue peak stress, matrix multiple cracking modes, and interface shear stress have been established. The effects of fiber volume fraction, fatigue peak stress and matrix cracking mode proportion on fatigue hysteresis dissipated energy and interface debonding and sliding have been analyzed. The experimental fatigue hysteresis dissipated energy of 2D C/SiC and SiC/SiC composites at room temperature, 550 °C, 800 °C, and 1100 °C in air, and 1200 °C in vacuum corresponding to different fatigue peak stresses and cycle numbers have been analyzed. The interface shear stress degradation rate has been obtained through comparing the experimental fatigue hysteresis dissipated energy with theoretical values. Fatigue damage evolution in C/SiC and SiC/SiC composites has been compared using damage parameters of fatigue hysteresis dissipated energy and interface shear stress degradation rate. It was found that the interface shear stress degradation rate increases at elevated temperature in air compared with that at room temperature, decreases with increasing loading frequency at room temperature, and increases with increasing fatigue peak stress at room and elevated temperatures.

Highlights

Ceramic materials possess high strength and high modulus at elevated temperatures.their use as structural components is severely limited due to the brittleness.Continuous fiber-reinforced ceramic-matrix composites (CMCs), are fabricated by incorporating fibers into ceramic matrices, and provide an alternative to conventional ceramics in high temperature applications
The CMCs exceed the capability of current nickel super alloys used in high-pressure turbines and provide increased efficiency [1]
The CMCs are subject to fatigue upon cyclic mechanical loads at fixed temperature with both room temperature and elevated temperature examined [2]

Summary

Introduction

Ceramic materials possess high strength and high modulus at elevated temperatures.their use as structural components is severely limited due to the brittleness.Continuous fiber-reinforced ceramic-matrix composites (CMCs), are fabricated by incorporating fibers into ceramic matrices, and provide an alternative to conventional ceramics in high temperature applications. Ceramic materials possess high strength and high modulus at elevated temperatures. Their use as structural components is severely limited due to the brittleness. Continuous fiber-reinforced ceramic-matrix composites (CMCs), are fabricated by incorporating fibers into ceramic matrices, and provide an alternative to conventional ceramics in high temperature applications. CMCs retain the strength, low weight, and high temperature capability while exhibiting less brittleness than ceramics. The CMCs exceed the capability of current nickel super alloys used in high-pressure turbines and provide increased efficiency [1]. The CMCs are subject to fatigue upon cyclic mechanical loads at fixed temperature with both room temperature and elevated temperature examined [2]. At intermediate temperatures, the chemical attack would cause damage inside of CMCs at constant mechanical load [3]; and creep degradation would occur in CMCs under constant mechanical load and constant temperature [4]

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Discussion

Conclusion