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Über dieses Buch

This book presents the relationships between tensile damage and fracture, fatigue hysteresis loops, stress-rupture, fatigue life and fatigue limit stress, and stochastic loading stress. Ceramic-matrix composites (CMCs) possess low material density (i.e., only 1/4 - 1/3 of high-temperature alloy) and high-temperature resistance, which can reduce cooling air and improve structure efficiency. Understanding the failure mechanisms and internal damage evolution represents an important step to ensure reliability and safety of CMCs. This book investigates damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) subjected to stochastic loading, including: (1) tensile damage and fracture of fiber-reinforced CMCs subjected to stochastic loading; (2) fatigue hysteresis loops of fiber-reinforced CMCs subjected to stochastic loading; (3) stress rupture of fiber-reinforced CMCs with stochastic loading at intermediate temperature; (4) fatigue life prediction of fiber-reinforced CMCs subjected to stochastic overloading stress at elevated temperature; and (5) fatigue limit stress prediction of fiber-reinforced CMCs with stochastic loading. This book helps the material scientists and engineering designers to understand and master the damage and fracture of ceramic-matrix composites under stochastic loading.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Tensile Damage and Fracture of Ceramic-Matrix Composites Subjected to Stochastic Loading

Abstract
In this chapter, effect of stochastic loading on tensile damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) is investigated. A micromechanical constitutive model is developed considering multiple damage mechanisms under stochastic tensile loading. Relationships between stochastic stress, composite tangent modulus, interface debonding, and fibers broken are established. Effects of composite constitutive properties (i.e., fiber volume, interface shear stress, interface debonding energy, and fiber strength) and composite damage state (i.e., saturation matrix crack spacing) on the tensile stress–strain curve, composite tangent modulus, interface debonding ratio, and fibers broken fraction are analyzed. Experimental tensile damage and fracture of unidirectional and 2D SiC/SiC composites subjected to different stochastic loading stresses are predicted.
Longbiao Li

Chapter 2. Hysteresis Loops of Ceramic-Matrix Composites Subjected to Stochastic Loading

Abstract
In this chapter, synergistic effects of stochastic loading sequence and interface wear on fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) are investigated. Based on the fatigue damage mechanisms of fiber sliding relative to matrix in the interface debonding region, the interface debonding length, unloading interface counter-slip length, and reloading interface new-slip length are determined using fracture mechanics approach. Effects of stochastic stress level, material properties, interface wear, and stochastic loading sequence on the interface slip and fatigue hysteresis loops are analyzed.
Longbiao Li

Chapter 3. Stress-Rupture of Ceramic-Matrix Composites Under Stochastic Loading at Intermediate Temperature

Abstract
In this chapter, stress-rupture of fiber-reinforced ceramic-matrix composites (CMCs) with stochastic loading at intermediate temperature is investigated. Four different stochastic loading sequences under stress-rupture are considered with a different loading time and time interval. Microstress field of the damaged CMCs and different damage models consider the effect of stochastic loading and time-dependent interface and fiber oxidation. Damage evolution of stress-rupture strain, interface debonding and interface oxidation ratio, and the broken fibers fraction versus time curves of SiC/SiC composite subjected to four different stochastic loading sequences are analyzed. Effects of composite constituent properties, damage state, and environmental temperature on damage evolution and lifetime of SiC/SiC composite are discussed. Experimental damage evolution and lifetime of SiC/SiC composite under stress-rupture with stochastic loading are predicted.
Longbiao Li

Chapter 4. Fatigue Life of Ceramic-Matrix Composites Subjected to Stochastic Loading at Elevated Temperature

Abstract
In this chapter, a micromechanical approach is developed to predict fatigue life of fiber-reinforced ceramic-matrix composites (CMCs) subjected to stochastic overloading stress at elevated temperature. Multiple elevated temperature fatigue damage mechanisms of interface wear and interface and fiber oxidation are considered in the analysis of elevated temperature fatigue damage evolution and fracture under stochastic overloading. Relationships between stochastic overloading stress level and occurrence applied cycle number, broken fibers fraction, and fatigue life decreasing rate are established. Experimental fatigue life S–N curves of C/SiC composites with different fiber preforms (i.e., unidirectional, cross-ply, 2D woven, 2.5D woven, and 3D braided) are predicted for different stochastic overloading stress levels and occurrence applied cycle number.
Longbiao Li

Chapter 5. Fatigue Damage and Fracture of Ceramic-Matrix Composites Subjected to Stochastic Loading

Abstract
In this chapter, a micromechanical fatigue limit stress model of fiber-reinforced ceramic-matrix composites (CMCs) subjected to stochastic overloading stress is developed. Fatigue limit stress of different C/SiC composites (i.e., unidirectional (UD), cross-ply (CP), 2D, 2.5D, and 3D C/SiC) is predicted based on the micromechanical fatigue damage models and fatigue failure criterion. Under cyclic fatigue loading, the fatigue damage and fracture under stochastic overloading stress at a different applied cycle number are characterized using two parameters of fatigue life decreasing rate and broken fibers fraction. Relationships between fatigue life decreasing rate, stochastic overloading stress, corresponding occurrence applied cycle number, and broken fibers fraction are analyzed.
Longbiao Li
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