Fatigue Hysteresis Research Articles

Damage Monitoring of Unidirectional C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading using A Hysteresis Loss Energy-Based Damage Parameter at Room and Elevated Temperatures

The damage evolution of unidirectional C/SiC ceramic-matrix composite (CMC) under cyclic fatigue loading has been investigated using a hysteresis loss energy-based damage parameter at room and elevated temperatures. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy versus cycle number have been analyzed. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different cycle number and peak stress has been estimated. The experimental evolution of fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter versus cycle number has been predicted for unidirectional C/SiC composite at room and elevated temperatures. The predicted results of interface shear stress degradation, stress–strain hysteresis loops corresponding to different number of applied cycles, fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter as a functions of cycle number agreed with experimental data. It was found that the fatigue hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.

Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air.

The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC) under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC) interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted.

Micromechanical Modeling for Fatigue Hysteresis Loops of Fiber-Reinforced Ceramic–Matrix Composites Under Multiple Loading Stress Levels

In this paper, the fatigue hysteresis loops of fiber-reinforced ceramic–matrix composites (CMCs) under multiple loading stress levels considering interface wear have been investigated using micromechanics approach. Under fatigue loading, fiber/matrix interface shear stress decreases with the increase of cycle number due to interface wear. Upon increasing of fatigue peak stress, the interface debonded length would propagate along the fiber/matrix interface. The difference of interface shear stress existing in the new and original debonded region would affect interface debonding and interface frictional slipping between fibers and matrix. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading, the interface debonded length, unloading interface counter-slip length and reloading interface new-slip length are determined by fracture mechanics approach. The fatigue hysteresis loop models under multiple peak stress levels have been developed. The effects of fiber volume fraction, fatigue peak stress, matrix crack spacing, interface debonding and interface wear on interface slip and fatigue hysteresis loops have been analyzed.

Relationship Between Hysteresis Dissipated Energy and Temperature Rising in Fiber-Reinforced Ceramic-Matrix Composites Under Cyclic Loading

In this paper, the relationship between hysteresis dissipated energy and temperature rising of the external surface in fiber-reinforced ceramic-matrix composites (CMCs) during the application of cyclic loading has been analyzed. The temperature rise, which is caused by frictional slip of fibers within the composite, is related to the hysteresis dissipated energy. Based on the fatigue hysteresis theories considering fibers failure, the hysteresis dissipated energy and a hysteresis dissipated energy-based damage parameter changing with the increase of cycle number have been investigated. The relationship between the hysteresis dissipated energy, a hysteresis dissipated energy-based damage parameter and a temperature rise-based damage parameter have been established. The experimental temperature rise-based damage parameter of unidirectional, cross-ply and 2D woven CMCs corresponding to different fatigue peak stresses and cycle numbers have been predicted. It was found that the temperature rise-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.

Modeling of fatigue hysteresis loops in C/SiC composite under multiple loading stress levels

In this paper, the tensile fatigue hysteresis behavior of unidirectional C/SiC ceramic-matrix composite under multiple loading stress levels has been investigated. The fatigue hysteresis loops and fatigue hysteresis loss energy corresponding to different number of applied cycles have been analyzed. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading/reloading, the unloading interface counter-slip length and reloading interface new-slip length are determined by fracture mechanics method. The fatigue hysteresis loops models corresponding to different interface slip cases under multiple loading stress levels have been developed. The relationships between fatigue hysteresis loops, fatigue hysteresis loss energy and interface slip have been analyzed. The fatigue hysteresis loops of unidirectional C/SiC composite corresponding to different number of applied cycles under multiple loading stress levels have been predicted.

A hysteresis dissipated energy-based damage parameter for life prediction of carbon fiber-reinforced ceramic-matrix composites under fatigue loading

Under fatigue loading, the stress–strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region. The area of hysteresis loops, i.e., the hysteresis dissipated energy, changes with the increase of cycle number, and can reveal fatigue damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding, interface slipping, interface wear, and fibers fracture. Based on the fatigue hysteresis theories considering fibers failure, the hysteresis dissipated energy and a hysteresis dissipated energy-based damage parameter changing with the increase of cycle number have been investigated. The relationships between the hysteresis dissipated energy, hysteresis dissipated energy-based damage parameter, stress–strain hysteresis loops, and fatigue damage mechanisms have been established. The effects of fatigue peak stress, stress ratio, matrix crack spacing and fiber volume content on the evolution of hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter as a function of cycle number have been analyzed. It was found that the hysteresis dissipated energy-based damage parameter is much more sensitive to interface debonding and interface frictional slipping compared with the hysteresis dissipated energy under fatigue loading, and can be used to reveal the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs. The experimental fatigue life S–N curves of unidirectional CMCs have been predicted using the present analysis.

Synergistic effect of arbitrary loading sequence and interface wear on the fatigue hysteresis loops of carbon fiber-reinforced ceramic-matrix composites

This study investigates the synergistic effect of arbitrary loading sequence and interface wear on the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs). Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region, the interface debonded length, unloading interface counter-slip length and reloading interface new-slip length are determined by fracture mechanics approach. The effects of peak stress, material properties, interface wear and arbitrary loading stress levels on the interface slip and fatigue hysteresis loops have been analyzed.

Tension-Tension Fatigue Behavior of Unidirectional C/Sic Ceramic-Matrix Composite at Room Temperature and 800 °C in Air Atmosphere

The tension-tension fatigue behavior of unidirectional C/SiC ceramic-matrix composite at room temperature and 800 °C under air has been investigated. The fatigue hysteresis modulus and fatigue hysteresis loss energy corresponding to different number of applied cycles have been analyzed. The fatigue hysteresis loops models for different interface slip cases have been derived based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading. The fiber/matrix interface shear stress has been estimated for different numbers of applied cycles. By combining the interface shear stress degradation model and fibers strength degradation model with fibers failure model, the tension-tension fatigue life S-N curves of unidirectional C/SiC composite at room temperature and 800 °C under air have been predicted.

Fatigue Hysteresis of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures

When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress–strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress–strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress–strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established.

Fatigue Life Prediction of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures. Part I: Experimental Analysis

This paper presents an experimental analysis on the fatigue behavior in C/SiC ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply and 2.5D woven, at room and elevated temperatures in air atmosphere. The experimental fatigue life S − N curves of C/SiC composites corresponding to different stress levels and test conditions have been obtained. The damage evolution processes under fatigue loading have been analyzed using fatigue hysteresis modulus and fatigue hysteresis loss energy. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different peak stress, fiber preforms and test conditions have been estimated. It was found that the degradation of interface shear stress and fibres strength caused by oxidation markedly decreases the fatigue life of C/SiC composites at elevated temperature.

Modeling for Fatigue Hysteresis Loops of Carbon Fiber-Reinforced Ceramic-Matrix Composites under Multiple Loading Stress Levels

In this paper, the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) under multiple loading stress levels considering interface wear has been investigated using micromechanical approach. Under fatigue loading, the fiber/matrix interface shear stress decreases with the increase of cycle number due to interface wear. Upon increasing of fatigue peak stress, the interface debonded length would propagate along the fiber/matrix interface. The difference of interface shear stress existed in the new and original debonded region would affect the interface debonding and interface frictional slipping between the fiber and the matrix. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading, the interface slip lengths, i.e., the interface debonded length, interface counter-slip length and interface new-slip length, are determined by fracture mechanics approach. The fatigue hysteresis loops models under multiple loading stress levels have been developed. The effects of single/multiple loading stress levels and different loading sequences on fatigue hysteresis loops have been investigated. The fatigue hysteresis loops of unidirectional C/SiC composite under multiple loading stress levels have been predicted.

Modeling the Effect of Interface Wear on Fatigue Hysteresis Behavior of Carbon Fiber-Reinforced Ceramic-Matrix Composites

An analytical method has been developed to investigate the effect of interface wear on fatigue hysteresis behavior in carbon fiber-reinforced ceramic-matrix composites (CMCs). The damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and interface wear, fibers fracture, slip and pull-out, have been considered. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Upon first loading to fatigue peak stress and subsequent cyclic loading, the fibers failure probabilities and fracture locations were determined by combining the interface wear model and fiber statistical failure model based on the assumption that the loads carried by broken and intact fibers satisfy the global load sharing criterion. The effects of matrix properties, i.e., matrix cracking characteristic strength and matrix Weibull modulus, interface properties, i.e., interface shear stress and interface debonded energy, fiber properties, i.e., fiber Weibull modulus and fiber characteristic strength, and cycle number on fibers failure, hysteresis loops and interface slip, have been investigated. The hysteresis loops under fatigue loading from the present analytical method were in good agreement with experimental data.

A hysteresis dissipated energy-based parameter for damage monitoring of carbon fiber-reinforced ceramic–matrix composites under fatigue loading

Under fatigue loading of fiber-reinforced ceramic–matrix composites (CMCs), the stress−strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region. The area of hysteresis loops, i.e., the hysteresis dissipated energy, changes with the increase of cycle number, which can reveal the fatigue damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding, interface slipping and interface wear. Based on the fatigue hysteresis theories, the relationships between hysteresis dissipated energy, hysteresis dissipated energy-based damage parameter, stress−strain hysteresis loops, and fatigue damage mechanisms have been established. The effects of fiber volume content, fatigue peak stress, fatigue stress ratio and matrix crack spacing on the evolution of the hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter as a function of cycle number have been analyzed. The experimental hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter of unidirectional CMCs corresponding to different fatigue peak stresses and cycle numbers have been predicted using the present analysis. It was found that the hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.

Micromechanics modeling of fatigue hysteresis loops in carbon fiber-reinforced ceramic-matrix composites

When fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress–strain hysteresis loops appear as the frictional slip occurred between the fiber and the matrix in the interface debonded region. The micromechanics fatigue hysteresis loops models of fiber-reinforced CMCs have been developed for different fiber preforms, i.e., unidirectional, cross-ply, and woven CMCs. The interface slip lengths, i.e., the interface debonded length upon first loading, unloading interface counter slip length, and reloading interface new slip length, were determined by fracture mechanics approach. The fatigue hysteresis loops of different interface debonding and slipping cases have been analyzed. The fatigue hysteresis loss energy is formulated in terms of fiber/matrix interface shear stress in the interface debonded region. When the interface shear stress decreases, the fatigue hysteresis loss energy first increases to the maximum value and then decreases to zero. By assuming the mechanical hysteresis behavior of cross-ply and woven CMCs was mainly controlled by interface frictional slip in the 0° plies or longitudinal yarns, considering the effect of matrix multicracking modes in cross-ply or woven CMCs, the fatigue hysteresis loops of fiber-reinforced CMCs with different fiber preforms under different peak stresses corresponding to different number of applied cycles have been predicted.

Fatigue hysteresis behavior of unidirectional C/SiC ceramic–matrix composite at room and elevated temperatures

Abstract In this paper, the tensile fatigue hysteresis behavior of unidirectional C/SiC composite at room and elevated temperatures in air atmosphere has been investigated. The fatigue hysteresis modulus and fatigue hysteresis loss energy corresponding to different number of applied cycles have been analyzed. Based on the damage mechanism of fiber slipping relative to matrix in the interface debonded region, the fatigue hysteresis loops models based upon the Coulomb friction law instead of a constant fiber/matrix interface shear stress usually assumed in the hysteresis analysis, have been developed. The relationships between the fatigue hysteresis loss energy, fatigue hysteresis loops, interface frictional slip and interface frictional coefficient have been established. When the fiber/matrix interface frictional coefficient degrades, the fatigue hysteresis loss energy first increases to the maximum value, and then decreases to zero; the fatigue hysteresis loops correspond to different interface frictional slip cases. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface frictional coefficient corresponding to different number of applied cycles, has been obtained. The variations of fatigue hysteresis modulus, fatigue hysteresis loss energy and interface frictional coefficient as a function of cycle number, have been analyzed for different fatigue peak stresses and test conditions. The fatigue hysteresis loops predicted using the hysteresis loops models and estimated fiber/matrix interface frictional coefficient agreed with experimental results.

Microstructure-sensitive investigation of magnesium alloy fatigue

This article presents results relating macroscopic fatigue behavior to microplasticity, twinning activity, and early fatigue crack formation in wrought magnesium alloy specimens of the AZ series. Experimental data were obtained by testing standard-sized samples prepared to be also suitable for direct microstructural quantification using scanning electron microscopy and electron back scatter diffraction for texture, grain-scale observations and fractography, as well as surface morphology measurements using white-light interferometry. In addition, in situ nondestructive monitoring of the fatigue behavior was performed by using the Acoustic Emission method. To describe the plastic anisotropy, tension–compression asymmetry, pseudoelasticity and their evolution as a function of fatigue loading, strain-control experiments of varying amplitude were conducted in several steps. Experimental measurements at different stages of fatigue life revealed repeatable occurrences of twinning–detwinning, which is further shown to be coupled with reversible surface roughening. It was also found that although tension twinning contributes considerably to overall plasticity, it could also give rise to crack initiation towards the end of the fatigue life. The role of the reported microplasticity effects was additionally explored using a Continuum Dislocation Dynamics Viscoplastic Self-Consistent (CDD-VPSC) model for the first two cycles of the fatigue life. The intention of this section was to incorporate the effect of twinning–detwinning into the CDD-VPSC model and subsequently to capture the experimental effects associated with changes in the fatigue hysteresis observed between first and second cycle. These simulation results were consistent with the hypothesis that detwinning is responsible for the anomalous hardening behavior during the tensile part of the cyclic loading in the first few cycles of loading. This observation was confirmed for several imposed strain amplitudes and was achieved by properly defining an appropriate boundary condition that allows surface morphology changes. Furthermore, the experimental test plan allowed the quantification of the fatigue life in terms of hysteresis loop parameters including plastic/elastic energy, residual stiffness, as well as mean and extreme stresses. Finally, an energy-based relationship for the evaluation of fatigue behavior based on the Ellyin–Kujawski formulation was found to provide life predictions that agree with obtained experimental information.

Micromechanical modeling of fatigue hysteresis behavior in carbon fiber-reinforced ceramic–matrix composites. Part I: Theoretical analysis

Under fatigue loading of fiber-reinforced ceramic–matrix composites (CMCs), fiber slipping relative to matrix in the interface debonded region upon unloading/reloading is the mainly fatigue damage mechanism. The shape, location and area of fatigue hysteresis loops would change with degradation of the interface shear stress for interface wear or interface oxidation. Based on the fatigue damage mechanism of interface frictional slip between fiber and matrix, the micromechanics fatigue hysteresis loops models corresponding to four different interface slip cases have been developed, in which the unloading interface counter-slip length and reloading interface new-slip length were determined by fracture mechanics approach. The fatigue hysteresis loss energy, fatigue hysteresis loops and interface slip of unidirectional, cross-ply and woven CMCs are formulated in terms of the interface shear stress. With decrease of the interface shear stress, the fatigue hysteresis loss energy increases to the maximum value first, and then decreases to 0; the fatigue hysteresis loops correspond to different interface slip cases. The effects of the fiber volume fraction, fatigue peak stress, fatigue stress amplitude, matrix crack spacing and matrix cracking mode on the fatigue hysteresis loss energy evolution with decrease of the interface shear stress have been analyzed. The range and extent of the interface frictional slip between fiber and matrix during fatigue loading would be decreased with increase of the fiber volume fraction and matrix crack spacing, increased with increase of the fatigue peak stress and fatigue stress amplitude, and greatly affected by matrix cracking mode in cross-ply CMCs.

Assessment of the interfacial properties from fatigue hysteresis loss energy in ceramic-matrix composites with different fiber preforms at room and elevated temperatures

The fiber/matrix interface shear stress is a key parameter in the fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this paper, the interface shear stress of three CMCs with different carbon fiber preforms, i.e., unidirectional C/SiC, cross-ply C/SiC and 2.5D woven C/SiC, has been estimated from fatigue hysteresis loss energy at room and elevated temperatures. Under fatigue loading, the fatigue hysteresis loss energy and fatigue hysteresis modulus versus the applied cycles have been analyzed. The theoretical relationships between the fatigue hysteresis loops, the fatigue hysteresis loss energy, the interface slip and the interface shear stress have been established. When the interface shear stress degrades, the fatigue hysteresis loss energy first increases to the maximum value, then decreases to zero; the fatigue hysteresis loops correspond to different interface slip cases. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the evolution of the interface shear stress versus the applied cycles of C/SiC composites has been analyzed. The effects of fiber preforms and test conditions on the interface shear stress degradation have been investigated. The fatigue hysteresis loops of unidirectional, cross-ply and 2.5D woven C/SiC composites have been predicted for different applied cycles at room and elevated temperatures.

Modeling fatigue hysteresis behavior of unidirectional C/SiC ceramic–matrix composite

In this paper, the fatigue hysteresis behavior of unidirectional C/SiC ceramic–matrix composite at room and elevated temperatures in air atmosphere has been investigated. The fatigue hysteresis modulus and fatigue hysteresis loss energy corresponding to different cycles have been analyzed. An approach to model fatigue hysteresis loops of unidirectional ceramic composites considering fiber failure has been developed. Based on the damage mechanism of fiber slipping relative to matrix under fatigue loading, the unloading interface counter-slip length and reloading interface new slip length are determined by fracture mechanics approach. The interface shear stress and broken fibers fraction corresponding to different cycles are obtained through comparing the experimental fatigue hysteresis loss energy with theoretical computational value considering fiber failure. The fatigue hysteresis loops of unidirectional C/SiC composite have been predicted for different number of cycles.

Fatigue hysteresis behavior of cross-ply C/SiC ceramic matrix composites at room and elevated temperatures

The tensile fatigue hysteresis behavior of cross-ply C/SiC composites at room and elevated temperatures in air atmosphere has been investigated in present analysis. The hysteresis modulus and hysteresis loss energy corresponding to different cycles have been analyzed. Based on damage mechanisms of fiber sliding relative to matrix in fiber/matrix interface debonded region upon unloading and subsequent reloading, the hysteresis loops models considering different matrix cracking modes have been developed. The hysteresis loss energy for strain energy lost per volume during corresponding cycle is formulated in terms of fiber/matrix interface shear stress. By comparing experimental hysteresis loss energy with computational values, fiber/matrix interface shear stress of cross-ply C/SiC composites at room and elevated temperatures has been estimated.