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Zirconia-toughened alumina (ZTA)-reinforced high-chromium cast iron (HCCI) composite materials were prepared using pressureless sintering method, and the effects of the type (titanium (Ti), nickel (Ni)) and content (10%, 12%) of active additives on the wettability and wear resistance were systematically studied. Result showed that the additive can enhance the wettability capacity between ZTA/HCCI composites interface, especially Ti, which reacted the chemical reaction and formed a transition layer in metallurgical combination. When the content of the Ti additive was 10%, the Brinell hardness (HB) of ZTA/HCCI composite was 573.1 N/mm2 at room temperature, and the wear-resistant properties were more than 3.8 times of pure HCCI. After thermal treatment, the HB and wear resistance of 10% Ti-ZTA/HCCI composites increased significantly which could reach 629.8 N/mm2 and were more than 4.3 times of the pure HCCI, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the 3D needle-punched C/SiC composite was fabricated using the chemical vapor deposition and reactive infiltration method. Four different fiber preforms were formed using the needled-punch technology. The PyC interphase was deposited on the surface of the fibers to increase the toughness of the composite under tensile loading. Cyclic loading/unloading tensile tests were conducted at different peak stresses. A micromechanical hysteresis constitutive relationship was developed considering damage mechanisms of matrix cracking, interface debonding and slip, and fiber's fracture and pullout. Using the developed hysteresis loops models and damage models, the hysteresis loops of four different types of 3D needle-punched C/SiC composites were predicted for different peak stresses. The hysteresis parameters of unloading residual strain, peak strain, hysteresis loops width, hysteresis loops area, interface slip ratio, and inverse tangent modulus were adopted to characterize the tensile damage evolution inside of composites. Relationship between composite's hysteresis behavior and microstructure damage evolution is established. It was found that the composite's hysteresis loops depend on the fiber's preform and interface properties. [ABSTRACT FROM AUTHOR]

Under thermal cyclic fatigue loading, temperature and cyclic-dependent damage mechanisms affect thermal fatigue damage evolution in fiber-reinforced ceramic-matrix composites (CMCs). Stress-strain hysteresis loops occur with the changing of temperature and correspond to internal damage evolution in CMCs. In this work, fatigue hysteresis-based damage features, including hysteresis-based dissipated energy, hysteresis modulus, hysteresis width, and peak strain, were developed to monitor thermal cyclic fatigue damage evolution in CMCs considering synergistic impacts of thermal and mechanical loading. Experimental thermal fatigue damage evolution of the 2.5D woven C/SiC composite subjected to various thermal fatigue loads were predicted with the newly developed fatigue hysteresis-related damage parameters. The effects of the composite's material features, peak stress, damage state, and cycle number on thermal fatigue damage evolution in the C/SiC composite were analyzed. [ABSTRACT FROM AUTHOR]

In this work, the synergetic effect of coating properties and fibrous architecture on the evolution of thermal stress was studied by finite element simulation. The numerical implementation was conducted on the plain-woven ceramic matrix composites coated with environmental barrier coatings (EBCs). Within the simulations, the microstructure of both coating layer and composite substrate was precisely modeled. The distributions of thermal residual stress of different yarn waviness and layer properties were simulated and compared. Their synergetic effect on the evolution of stress was then investigated by comparing the simulated results under different mechanical loadings which can enlarge the nonuniform distribution of stress induced by fibrous architecture. The results show that the cooling process causes considerable thermal residual stress in each layer of a Si/mullite/Yb2Si2O7 EBCs. Similar to the layer properties of coatings, the fibrous architecture of the composite substrate also plays an important role in the stress distribution in the coatings. Thus, it can be concluded that an adequate prediction of the local stress distribution and the failure modes for the EBCs requires a realistic representation of fibrous architecture as well as the coating layers. The former is usually ignored in the previous studies. [ABSTRACT FROM AUTHOR]

In this paper, the stress-dependent matrix multiple fractures of fiber-reinforced ceramic-matrix composites (CMCs) with fiber oxidation and fracture is investigated. The shear-lag model is combined with the fiber oxidation and fracture models, and the fiber/matrix interface debonding criterion is adopted to determine the micro-stress field of the damaged fiber-reinforced CMCs. The effects of the fiber volume, interface shear stress, interface debonding energy, oxidation temperature and time on the stress-dependent matrix multiple fractures, interface debonding and oxidation, and fiber fracture are discussed. When the fiber volume fraction and the interface shear stress in the debonding region increased, the matrix first cracking stress and saturation cracking stress increased, the saturation matrix cracking space decreased, and the matrix multiple fracture evolution rate increased. When the interface debonding energy and the interface shear stress in the oxidation region increased, the matrix cracking density increased. When the oxidation temperature and oxidation duration increased, the matrix cracking density decreased. The experimental matrix multiple fractures of unidirectional C/SiC, SiC/SiC, mini-SiC/SiC, SiC/CAS, SiC/CAS-II, and SiC/borosilicate composites are predicted. [ABSTRACT FROM AUTHOR]

In this paper, the synergistic effects of interface slip and fiber fracture on stress-dependent mechanical hysteresis of SiC/SiC ceramic-matrix minicomposites (mini-CMCs) are investigated. Upon cyclic loading/unloading, the relative slip between the fiber and the matrix, and the fracture fiber affect the hysteresis behavior of mini-CMCs. The micro-stress field of the damaged mini-CMCs is obtained through shear-lag analysis, and cyclic loading/unloading hysteresis strain is related with the stress level, interface slip, and broken fiber. The effects of constituent properties and internal damage state on cyclic loading/unloading interface slip and hysteresis loops of SiC/SiC minicomposite are analyzed. The experimental matrix cracking density, stress-dependent mechanical hysteresis and interface slip of Hi-NicalonTM, Hi-NicalonTM Type S, and TyrannoTM ZMI SiC/SiC minicomposites are predicted. The interface debonding and slip range, and mechanical hysteresis loops of SiC/SiC minicomposites are affected by the stress level, constituent properties of the fiber volume, interface properties, and damage state of matrix cracking and broken fiber subjected to cyclic tensile loading. [ABSTRACT FROM AUTHOR]

A model for predicting residual stiffness of unidirectional SiC/SiC composite in a stress-oxygen environment over 900°C is developed based on an improved two-stage oxidation kinetics model. Two differential equations relating to the oxygen concentration are derived according to the conservation of mass. As a result, the thickness of the oxide on the fiber, the matrix, and the length of the interface consumed by oxidation can be calculated. The elastic modulus of the fiber and its stress redistribution are analyzed considering the change of the crack in different stress conditions, the oxidation defect on the fiber, the recession length of the interface, and the residual stress caused by the interface debonding. The residual stiffness of the SiC/SiC composite versus time after oxidation is drawn as curves under different stress levels which shows that the applied load does not affect the oxidation behavior of the matrix; it only changes the oxidation time of the composite. In addition, the residual stiffness of the composite decreases rapidly in the beginning for a while, then the degenerate rate stays stable until the interface is fully consumed. The predicted residual stiffness from the model is consistent with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper, the effect of interface damage on the tensile damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) after thermal fatigue loading is investigated. The damage mechanisms of matrix cracking, fiber/matrix interface debonding and wear, interface and fiber oxidation, and fiber failure after thermal fatigue loading are considered in the tensile stress-strain behavior prediction. The relationships between the thermal fatigue temperature, applied cycle number, composite internal damage, and tensile damage and fracture are established. The effects of thermal fatigue temperature, thermal cycle number, fiber volume, interface shear stress, fiber strength, and fiber Weibull modulus on the tensile damage and fracture of fiber-reinforced CMCs subjected to the thermal fatigue loading are analyzed. The experimental tensile stress-strain curves of different C/SiC composites with and without thermal fatigue loading are predicted. When the thermal fatigue temperature and applied cycle number increase, the composite tensile strength and failure strain decrease, the interface debonding ratio, interface oxidation ratio, and broken fibers fraction increase at low applied stress level. [ABSTRACT FROM AUTHOR]

In this paper, the time-dependent matrix fracture of carbon fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated considering the interface oxidation. The time-dependent fiber/matrix interface oxidation length and temperature-dependent fiber/matrix interface shear stress in the oxidation and deboned region, interface debonded energy, fiber and matrix modulus and matrix fracture energy are considered in the analysis for the micro stress field, interface debonding criterion and critical matrix strain energy (CMSE) model. The relationships between the time, temperature, applied stress, fiber/matrix interface debonding, and matrix fracture are established. The effects of fiber/matrix interface shear stress, fiber/matrix interface frictional coefficient, fiber/matrix interface debonded energy, and matrix fracture energy on the matrix cracking density and interface oxidation ratio are discussed for different temperatures and oxidation time. The experimental matrix cracking density and interface oxidation ratio for unidirectional C/SiC composite at different testing temperatures and oxidation time are predicted. [ABSTRACT FROM AUTHOR]

In this paper, the synergistic effects of temperature and time on the proportional limit stress (PLS) of SiC/SiC composites are investigated. The temperature-dependent constituent properties and time-dependent interface oxidation are considered to determine the PLS. The effects of fiber volume fraction, interface shear stress, interface debonded energy and matrix fracture energy on the temperature/time-dependent PLS and interface debonded length of SiC/SiC composite are discussed. The experimental PLS of SiC/SiC composite corresponding to different temperature and time are predicted. [ABSTRACT FROM AUTHOR]

The mechanism of crack propagation in the interphase plays an important role in the failure procedure of ceramic matrix composites (CMCs). The aim of this paper is to examine the effect of interphase thickness on the propagation of a pre-defined matrix crack. A SiC/SiC unit-cell with different thicknesses of BN interphase was analyzed using an approach based on the extended finite element method (XFEM). With this approach, the initiation of new cracks and propagation of primary crack in the interphase can be simulated without the presupposed crack path. The crack patterns and stress-strain responses of unit-cells with different thickness were compared. The initiation and propagation of the secondary crack/cracks in the interphase provide insight into the toughening mechanism and design of interfaces/interphases of CMCs. [ABSTRACT FROM AUTHOR]

In this paper, the time-dependent damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) are investigated considering fiber oxidation and fracture at an elevated temperature. The shear-lag model combined with the fiber/matrix interface oxidation model, the interface debonding criterion, fiber strength degradation model and fiber failure model is adopted to analyze the microstress field in the damaged composite. The relationships between the first steady-state matrix cracking stress, composite tensile strength, fiber/matrix interface debonding and sliding, oxidation temperature and oxidation time are established. The effects of fiber volume fraction, fiber/matrix interface shear stress, fiber strength and oxidation temperature on the evolution of first steady-state matrix cracking stress and composite tensile strength versus the oxidation time are analyzed. The first steady-state matrix cracking stress and composite tensile strength of 2D C/SiC and 2D C/[SiC-B4C] composites after oxidation at 700°C, 1200°C and 1300°C in air atmosphere are predicted for different oxidation time. [ABSTRACT FROM AUTHOR]

In this paper, the synergistic effects of fiber/matrix interface wear and fibers fracture on matrix multiple cracking in fiber-reinforced ceramic-matrix composites (CMCs) are investigated using the critical matrix strain energy (CMSE) criterion. The shear-lag model combined with the fiber/matrix interface wear model, fibers fracture model and the fiber/matrix interface fracture mechanics debonding criterion is adopted to analyze the fiber and matrix axial stress distribution inside of the damaged composite. The relationships between the matrix multiple cracking, fatigue peak stress, applied cyclic number, fiber/matrix interface wear and debonding and fibers failure are established. The effects of fiber volume fraction, fiber/matrix interface shear stress, fiber/matrix interface debonded energy, cycle number, fatigue peak stress and fibers strength on matrix multiple cracking evolution are discussed. Comparisons of matrix multiple cracking with/without cyclic fatigue loading are analyzed. The experimental multiple matrix cracking of unidirectional SiC/CAS, SiC/CAS-II, SiC/Borosilicate and mini-SiC/SiC composites with/without cyclic fatigue loading are predicted. [ABSTRACT FROM AUTHOR]