Cross-ply Ceramic Matrix Composites Research Articles

Thermomechanical fatigue damage evolution of fiber-reinforced ceramic–matrix composites under multiple loading sequences

In this article, the thermomechanical fatigue damage evolution of fiber-reinforced ceramic–matrix composites subjected to multiple loading sequences is investigated. The damage evolution models considering synergistic coupling effects of thermomechanical fatigue loading sequences, thermal cyclic temperature, and multiple thermomechanical fatigue damage mechanisms (i.e. matrix multi-cracking, fiber/matrix interface debonding/sliding/wear) are developed. The effects of composite material properties, peak stress, and matrix crack spacing on the thermomechanical fatigue damage evolution of fiber-reinforced ceramic–matrix composites are discussed. Comparisons of damage evolution between the in-phase and the out-of-phase thermomechanical fatigue loading under multiple loading sequences are performed. The thermomechanical fatigue hysteresis energy, hysteresis modulus, peak strain, and interface debonded length of cross-ply ceramic–matrix composites subjected to different loading sequences are predicted. The damage under thermomechanical fatigue multiple loading sequences is much more serious than that under thermomechanical fatigue single peak stress level.

Synergistic effects of temperature, oxidation, and stress level on fatigue hysteresis behavior of cross-ply ceramic-matrix composites at room and elevated temperatures under cyclic loading

In this paper, the synergistic effects of temperature, oxidation, and stress level on the fatigue hysteresis behavior of cross-ply SiC/CAS ceramic-matrix composites (CMCs) at room temperature and 700 and 850 °C in air atmosphere has been investigated. The relationships between the fatigue hysteresis loops, fatigue hysteresis-dissipated energy, fatigue hysteresis modulus, and the fiber/matrix interface shear stress have been established using the hysteresis loop models considering different matrix cracking modes. The fatigue damage evolution process of SiC/CAS composite under tension–tension fatigue loading has been analyzed using the hysteresis loops. By comparing the experimental fatigue hysteresis-dissipated energy with theoretical computational values, the interface shear stress of SiC/CAS composite were obtained for different cycle numbers and fatigue peak stress. It was found that at elevated temperature in air, the interface shear stress degradation rate is much more affected by the fatigue peak stress than that at room temperature due to interface oxidation. The comparisons of interface shear stress evolution between unidirectional SiC/MAS and SiC/CAS, 2D SiC/SiC, and cross-ply SiC/CAS composites have been analyzed.

Damage development and lifetime prediction of cross-ply ceramic-matrix composites subjected to cyclic loading at room and elevated temperatures

ABSTRACTIn this paper, the damage development and lifetime prediction of fibre-reinforced ceramic-matrix composites subjected to cyclic loading at elevated temperatures in oxidising atmosphere have been investigated. Considering the damage mechanisms of matrix cracking, interface debonding, interface wear and interface oxidation, the damage evolution of fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain, interface shear stress and broken fibres fraction have been analysed. The relationships between damage parameters and internal damage of matrix cracking, interface debonding and slipping, and fibres fracture have been established. The experimental fatigue hysteresis, interface slip lengths, peak strain, and the fatigue life curves of cross-ply CMCs under cyclic loading at elevated temperature have been predicted. The different fatigue behaviour in unidirectional and cross-ply CMCs at room and elevated temperatures subjected to low-cycle and high-cycle fatigue has been discussed.

Synergistic effects of temperature, oxidation, loading frequency and stress-rupture on damage evolution of cross-ply ceramic-matrix composites under cyclic fatigue loading at elevated temperatures in oxidizing atmosphere

In this paper, the synergistic effects of temperature, oxidation, loading frequency and stress-rupture on damage evolution of cross-ply ceramic-matrix composites (CMCs) under cyclic fatigue loading at elevated temperatures in oxidizing atmosphere have been investigated. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the micro stress field of the damaged composite considering interface wear and interface oxidation. The damage parameters of fatigue hysteresis dissipated energy, fatigue hysteresis modulus, and fatigue peak strain have been used to monitor the damage evolution inside of CMCs. The relationships between damage parameters and internal damage of matrix cracking, interface debonding and slipping have been established. The experimental fatigue hysteresis, interface slip lengths and peak strain of cross-ply SiC/MAS composite under cyclic fatigue loading at different testing temperatures, loading frequency and stress-rupture time in air condition have been predicted.

Damage evolution of cross-ply ceramic-matrix composites under stress-rupture and cyclic loading at elevated temperatures in oxidizing atmosphere

In this paper, the damage evolution of cross-ply ceramic-matrix composites (CMCs) under stress-rupture and cyclic loading at elevated temperatures in oxidizing atmosphere has been investigated. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the micro stress field of the damaged composite considering matrix multicracking, interface debonding/wear/oxidation/slip. The damage parameters of fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain and fatigue hysteresis width have been used to monitor the damage evolution inside of CMCs. The relationship between damage parameters and internal damage of matrix multicracking, interface debonding/slip has been established. The experimental fatigue hysteresis loops, interface slip lengths, fatigue hysteresis dissipated energy and peak strain of cross-ply SiC/MAS composite under cyclic fatigue and stress-rupture at 566°C and 1093°C in air have been predicted.

Effect of Matrix Multicracking on the Hysteresis Loops of Carbon-Fiber-Reinforced Cross-Ply Ceramic-Matrix Composites

The effect of matrix multicracking on the stress-strain hysteresis loops of cross-ply C/SiC ceramic-matrix composites (CMCs) under cyclic loading/unloading was investigated. When matrix multicracking and fiber/matrix interface debonding occur in the 0° plies, fiber slipping relative to the matrix in the debonded region of interface is the mainly reason for occurrence of the loops. The interfacial slip lengths, i.e., the debonded lengths of interface are determined, with consideration of matrix multicracking in the 90° and 0° plies, by using the fracture mechanics approach. The effects of peak stress, fiber volume content, fiber/matrix interfacial shear stress, and number of cycles on the hysteresis loops are analyzed. The stress-strain hysteresis loops of cross-ply C/SiC composites corresponding to different peak stresses and numbers of cycles are predicted.

Synergistic Effects of Frequency and Temperature on Damage Evolution and Life Prediction of Cross-Ply Ceramic Matrix Composites under Tension-Tension Fatigue Loading

In this paper, the synergistic effects of loading frequency and testing temperature on the fatigue damage evolution and life prediction of cross-ply SiC/MAS ceramic-matrix composite have been investigated. The damage parameters of the fatigue hysteresis modulus, fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of SiC/MAS composite. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S–N curves of SiC/MAS composite under the loading frequency of 1 and 10 Hz at 566 °C and 1093 °C in air condition have been predicted. The synergistic effects of the loading frequency and testing temperature on the degradation rate of fatigue hysteresis dissipated energy and the interface shear stress have been analyzed.

Comparison of Cyclic Hysteresis Behavior between Cross-Ply C/SiC and SiC/SiC Ceramic-Matrix Composites.

In this paper, the comparison of cyclic hysteresis behavior between cross-ply C/SiC and SiC/SiC ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in the matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in the 0° plies are considered as the major reason for hysteresis loops of cross-ply CMCs. The hysteresis loops of cross-ply C/SiC and SiC/SiC composites corresponding to different peak stresses have been predicted using present analysis. The damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire matrix cracking modes of the composite, and the hysteresis dissipated energy increase with increasing peak stress. The damage parameter and hysteresis dissipated energy of C/SiC composite under low peak stress are higher than that of SiC/SiC composite; However, at high peak stress, the damage extent inside of cross-ply SiC/SiC composite is higher than that of C/SiC composite as more transverse cracks and matrix cracks connect together.

A Three-Phase Shear-Lag Model for Longitudinal Cracking of a Ceramic Matrix Composite Ply With Thick Fiber Coatings

During progressive cracking of cross-ply ceramic matrix composites (CMCs), load is transferred from the fiber to the matrix in the longitudinal (0 deg) ply via shear through a compliant interphase layer, also referred to as the coating. In the material system of interest, this coating has significant thickness relative to the fiber diameter. The damage process in the cross-ply CMC is observed to be as follows: (1) elastic deformation, (2) cracking of the transverse plies, (3) matrix cracking within the longitudinal plies, (4) failure of longitudinal fibers, and (5) pullout of the cracked fibers from the matrix. In this paper, the focus is on the longitudinal (0 deg) ply. Existing shear-lag models do not fully represent either the stress transfer through the coating or the true accumulations of shear and normal stresses in the matrix. In the current study, a model is developed that takes into account both of these factors to provide a more accurate, analytical representation of the stress distribution and progressive damage accumulation in a longitudinal CMC ply.

Modeling for Matrix Multicracking Evolution of Cross-ply Ceramic-Matrix Composites Using Energy Balance Approach

The matrix multicracking evolution of cross-ply ceramic-matrix composites (CMCs) has been investigated using energy balance approach. The multicracking of cross-ply CMCs was classified into five modes, i.e., (1) mode 1: transverse multicracking; (2) mode 2: transverse multicracking and matrix multicracking with perfect fiber/matrix interface bonding; (3) mode 3: transverse multicracking and matrix multicracking with fiber/matrix interface debonding; (4) mode 4: matrix multicracking with perfect fiber/matrix interface bonding; and (5) mode 5: matrix multicracking with fiber/matrix interface debonding. The stress distributions of four cracking modes, i.e., mode 1, mode 2, mode 3 and mode 5, are analysed using shear-lag model. The matrix multicracking evolution of mode 1, mode 2, mode 3 and mode 5, has been determined using energy balance approach. The effects of ply thickness and fiber volume fraction on matrix multicracking evolution of cross-ply CMCs have been investigated.

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.

Effect of matrix cracking on hysteresis behavior of cross-ply ceramic matrix composites

The effect of matrix cracking on hysteresis behavior of cross-ply ceramic matrix composites is investigated in the present analysis. The cracking of cross-ply ceramic composites was classified into five modes, where cracking mode 3 and mode 5 involve matrix cracking and fiber/matrix interface debonding in 0° ply. The matrix crack space and interface debonded length are obtained by matrix statistical cracking model and fracture mechanics interface debonding criterion. Based on the damage mechanisms of fiber sliding relative to matrix in the interface debonded region, the unloading interface reverse slip length and reloading interface new slip length of cracking mode 3 and mode 5 are determined by the fracture mechanics approach. The hysteresis loops of four different cases for cracking mode 3 and mode 5 are derived respectively. The hysteresis loss energy as a function of interface shear stress of mode 3 and mode 5 are analyzed. The theoretical results have been compared with experimental data of two different cross-ply ceramic composites.

Effect of Matrix Cracks on Damping in Unidirectional and Cross-Ply Ceramic Matrix Composites

The paper elucidates the methodsof estimating damping in ceramic matrix composites (CMC) with matrix cracks. Unidirectional composites with bridging matrix cracks and cross-ply laminates with tunneling cracks in transverse layers and bridging cracks in longitudinal layers are considered. It is shown that bridging matrix cracksdra matically increase damping in unidirectional CMC due to a dissipation of energy along damaged sections of the fiber–matrix interface (interfacial friction). Such friction is absent in the case of tunneling cracks in transverse layers of cross-ply laminates where the changes in damping due to a degradation of the stiffness remain small. However, damping in cross-ply laminates abruptly increases, if bridging cracks appear in the longitudinal layers.

Matrix crack evolution in SiC fiber/glass matrix cross-ply laminates

Matrix crack evolution was studied for SiC fiber-reinforced glass-matrix cross-ply laminates. A novel in situ SEM (scanning electron microscope) observation was conducted to measure the fiber/matrix debonding and sliding in 0° plies using specimens with parallel micro-lines printed on the surfaces. Interfacial debondings were found to grow intermittently as the applied stress increased. The debonding length distribution depends on the number of 90° plies as well as the type of damage modes. An analytical model for the matrix crack evolution was proposed using the energy balance calculation based on Kuo and Chou (Kuo WS, Chou TW. Multiple cracking of unidirectinal and cross-ply ceramic matrix composites. J Am Ceram Soc 1995;78(3):745–755), with the modification of including the effects of damage mode interaction as well as Poisson contraction in the debonded regions. The predicted evolution agrees well with the experimental one.

Modeling of Fatigue in Cross-Ply Ceramic Matrix Composites

This study proposes a methodology for modeling the fatigue response of cross-ply ceramic matrix composites (CMCs). The micromechanics based analysis and failure criteria are formulated to model stress-strain hysteresis, strain ratchetting and S-N behavior specific to room-temperature cyclic loading environments. The damage mechanisms considered are matrix cracking in the 90° and 0° plies, fiber/matrix interfacial debonding, fiber fracture, and fiber pull-out. These damage modes are modeled by a set of failure criteria with a minimum reliance on empirical data which can be easily employed in a variety of numerical and analytical techniques. The predicted results are found to be in good agreement with the experimental data; however, it is observed that the assumed degradation in the frictional resistance along the fiber/matrix interface plays a dominant role in determining the fatigue response.

Multiple Cracking of Unidirectional and Cross‐PlyCeramic Matrix Composites

This paper examines the multiple cracking behavior of unidirectional and cross‐ply ceramic matrix composites. For unidirectional composites, a model of concentric cylinders with finite crack spacing and debonding length is introduced. Stresses in the fiber and matrix are found and then applied to predict the composite moduli. Using an energy balance method, critical stresses for matrix cracking initiation are predicted. Effects of interfacial shear stress, debonding length and bonding energy on the critical stress are studied. All the three composite systems examined show that the critical stress for the completely debonded case is lower than that for the perfectly bonded case. For cross‐ply composites, an extensive study has been made for the transverse cracking in 90° plies and the matrix cracking in 0° plies. One transverse cracking and four matrix cracking modes are studied, and closed‐form solutions of the critical stresses are obtained. The results indicate that the case of combined matrix and transverse crackings with associated fiber/matrix interfacial sliding in the 0° plies gives the lowest critical stress for matrix cracking. The theoretical predictions are compared with experimental data of SiC/CAS cross‐ply composites; both results demonstrated that an increase in the transverse ply thickness reduces the critical stress for matrix cracking in the longitudinal plies. The effects of fiber volume fraction and fiber modulus on the critical stress have been quantified. Thermal residual stresses are included in the analysis.

Modeling behavior of cross-ply ceramic matrix composites under quasi-static loading

This paper presents a simplified analysis (model and failure criteria) for predicting the stress-strain responce of cross-ply fiber-reinforced ceramic composite laminates under quasi-static loading and unloading conditions. The model formulation is an extension of the modified shear-lag theory previously introduced by the authors for analyzing unidirectional laminates for the same loading conditions. The present formulation considers a general damage state consisting of matrix cracking in both the transverse and longitudinal plies, as well as fiber failure. These damage modes are modeled by a set of failure criteria with the minimum reliance on empirical data, and can be easily employed in a variety of numerical or analytical methods. The criteria used to estimate the extent of matrix cracking and interfacial debonding are closed-form and require the basic material properties. The failure criterion for fiber failure requires a priori knowledge of a single empirical constant. This parameter, however, may be determined without microscopic investigation of the laminate microstructure. The results from the present simplified analysis match well with the experimental data.

Matrix cracking in crossply ceramic matrix composites under quasi-static and cyclic loading

Experimental data are presented for the development of 90° ply and 0° ply cracking in two crossply silicon carbide fibre/calcium aluminosilicate matrix laminates under quasi-static loading. under mechanical fatigue loading it is found that there is an increase in ply crack densities and a corresponding laminate stiffness reduction with cycling. Possible mechanisms to account for these observations are proposed. A model is presented which describes the stress/strain behaviour as a function of crack densities based on assumptions of frictional load transfer between fibre and matrix in the longitudinal plies and elastic bonding between the longitudinal and transverse plies.