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In this paper, the synergistic effects of fibre debonding and fracturing on vibration damping in fibre-reinforced ceramic-matrix composites (CMCs) is investigated. The relationships between the damping of the CMCs, the damping of the fibre and the matrix, the damping caused by the frictional slip between the fibre and the matrix, and the fibre debonding and fracturing are established. The effects of the fibre volume, matrix crack spacing, interface shear stress, interface debonding energy, fibre strength and fibre Weibull modulus on the damping of the CMCs, the interface debonding and slip between the fibre and the matrix, and the fibre broken fraction are analysed. The damping of the unidirectional CMCs with and without considering the fibre failure is discussed. The experimental damping of a 2D C/SiC composite is predicted using the present analysis. When the fibre volume increases, the composite damping decreases, due to the decrease in the interface debonding and slip length and the broken fibre fraction. Considering the fibre failure, the composite damping decreases, due to the increase in the fibre broken fraction. When the fibre strength and fibre Weibull modulus increase, the composite damping increases, due to the decrease of the interface debonding length, interface slip length, and broken fibre fraction.

In this paper, the effect of the interface properties between the fibre and the matrix on the nonlinear behaviour of long-fibre-reinforced unidirectional ceramic-matrix mini-composites (mini-CMCs) is investigated. The tensile nonlinear constitutive relationship and fatigue loading/unloading constitutive relationship are developed considering the different damage mechanisms of cracking in the matrix, debonding in the interface, and gradually the broken fibres. The relationships of the interface properties between the fibre and the matrix, the nonlinear tensile strain, and the fatigue loading/unloading hysteresis loops are established. The effects of the interface properties between the fibre and the matrix on the nonlinear tensile and fatigue loading/unloading damage evolution are analysed. The nonlinear tensile strain at the damage stage and the fracture strain of mini-CMCs decrease with the strong interface properties; and the fatigue loading/unloading hysteresis loops area and strain decrease, and the hysteresis modulus increases with the strong interface properties. The experimental tensile stress-strain curves and fatigue loading/unloading hysteresis loops of the Hi-NicalonTM and TyrannoTM SiC/SiC mini-composites are predicted corresponding to the different interface properties.

In this paper, the tensile damage and fracture process of fibre-reinforced ceramic-matrix composites (CMCs) under the effect of pre-exposure at elevated temperatures are investigated. The damage mechanisms of the interface oxidation and the fibre failure are considered in the stress analysis, matrix multi-cracking, interface debonding and fibre failure. Combining the stress analysis and damage models, the tensile stress-strain curves of the fibre-reinforced CMCs for the different damage stages can be obtained. The effects of the pre-exposure temperature and time, interface shear stress, fibre strength and fibre Weibull modulus on the tensile damage and fracture processes are analysed. The experimental tensile damage and fracture process of the fibre-reinforced CMCs with the different fibre preforms are predicted for the different pre-exposure temperatures and times

In this paper, the temperature-dependent proportional limit stress of carbon fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated using the energy balance approach. The temperature-dependent micromechanical parameters of fiber and matrix modulus, fiber/matrix interface shear stress and interface debonded energy, and matrix fracture energy are incorporated into the analysis of the micro stress analysis, fiber/matrix interface debonding criterion and energy balance approach. The relationships between the proportional limit stress, fiber/matrix interface debonding and temperature are established. The effects of fiber volume fraction, fiber/matrix interface shear stress, interface frictional coefficient, interface debonded energy and matrix fracture energy on the proportional limit stress and fiber/matrix interface debonding length versus temperature curves are discussed. The experimental proportional limit stress and fiber/matrix interface debonding length of 2D C/SiC composite at elevated temperatures of 973K and 1273K are predicted. For C/SiC composite, the proportional limit stress of C/SiC composite increases with temperature, due to the increasing of fiber/matrix interface shear stress and decreasing of the thermal residual stress.

In this paper, the time-dependent matrix multi-cracking of SiC/SiC ceramic-matrix composites (CMCs) has been investigated considering the fibre/matrix interface oxidation. The time-dependent interface oxidation length and temperature-dependent fibre/matrix interface shear stress in the oxidation and the de-bonded region, the interface de-bonded energy, the fibre and matrix modulus and the matrix fracture energy are considered in the analysis for the micro stress field, the interface debonding criterion and the critical matrix strain energy model. The effects of the fibre volume fraction, the fibre/matrix interface shear stress, the fibre/matrix interface frictional coefficient, the fibre/matrix interface de-bonded energy and the matrix fracture energy on the matrix multi-cracking density and the interface oxidation ratio of SiC/SiC composite are discussed for the different temperatures and oxidation time. The experimental matrix multi-cracking density and fibre/matrix interface oxidation ratio are predicted for unidirectional and mini SiC/SiC composites at different testing temperatures and oxidation time.

In this paper, the synergistic effects of the loading frequency and testing temperature on the fatigue hysteresis behaviour of a cross-ply SiC/MAS ceramic-matrix composite are investigated. The fatigue stress-strain hysteresis loop models, considering different matrix cracking modes, are developed to establish the relationships among the fatigue hysteresis loops, fatigue hysteresis dissipated energy and fibre/matrix interface shear stress. Comparing the experimental fatigue hysteresis dissipated energy with the theoretical values, the fibre/matrix interface shear stress of the cross-ply SiC/MAS composite under the loading frequency of 1 and 10 Hz at 566 °C and 1093 °C in air conditions are obtained for different applied cycle numbers and fatigue peak stresses. At a low loading frequency of 1 Hz, the fibre/matrix interface shear stress and interface shear stress degradation rate of the cross-ply SiC/MAS are higher than that at the loading frequency of 10 Hz. At 1093 °C in air conditions, the fibre/matrix interface shear stress and interface shear stress degradation rate of the cross-ply SiC/MAS are higher than that at 566 °C in air conditions.

In this paper, the matrix multi-cracking evolution of fibre-reinforced ceramic-matrix composites (CMCs) considering fibre fracture have been investigated using the critical matrix strain energy criterion. The shear-lag model combined with the fibre fracture model and fibre/matrix interface debonding criterion is adopted to analyse the fibre and matrix axial stress distribution inside the damaged composite. The effects of the fibre volume fraction, the fibre/matrix interface shear stress, the fibre/matrix interface debonded energy, the fibre Weibull modulus and the fibre strength on the stress-dependent matrix multi-cracking development are discussed. The experimental matrix multi-cracking evolution of the unidirectional SiC/CAS, SiC/CAS-II, SiC/SiC, SiC/Borosilicate and mini-SiC/SiC composites are predicted.

In this paper, we present a sample of 21 repeating fast radio bursts (FRBs) detected by different radio instruments before September 2021. Using the Anderson–Darling test, we compared the distributions of extra-Galactic dispersion measure (DME) of non-repeating FRBs, repeating FRBs and all FRBs. It was found that the DME values of three sub-samples are log-normally distributed. The DME of repeaters and non-repeaters were drawn from a different distribution on basis of the Mann–Whitney–Wilcoxon test. In addition, assuming that the non-repeating FRBs identified currently may be potentially repeators, i.e., the repeating FRBs to be universal and representative, one can utilize the averaged fluence of repeating FRBs as an indication from which to derive an apparent intensity distribution function (IDF) with a power-law index of a1=1.10±0.14 (a2=1.01±0.16, the observed fluence as a statistical variant), which is in good agreement with the previous IDF of 16 non-repeating FRBs found by Li et al. Based on the above statistics of repeating and non-repeating FRBs, we propose that both types of FRBs may have different cosmological origins, spatial distributions and circum-burst environments. Interestingly, the differential luminosity distributions of repeating and non-repeating FRBs can also be well described by a broken power-law function with the same power-law index of −1.4.

In this paper, the 12k T-700TM Multiaxial-Warp-Knitting–Needle (MWK–N) C/SiC composite and pin were designed and fabricated using the isothermal chemical vapor infiltration (ICVI) method. The composite’s microstructure and mechanical properties were examined by subjection to tensile and interlaminar shear tests. Three types of double-shear tests were conducted for C/SiC pins, including shear loading perpendicularly, along, and at 45° off-axial to the lamination. The fracture surface of the tensile and shear failure specimens was observed under scanning electronic microscope (SEM). The relationships between the composite’s microstructure, mechanical properties, and damage mechanisms were established. The composite’s average tensile strength was σuts = 68.3 MPa and the average interlaminar shear strength was τu = 38.7 MPa. For MWK–N–C/SiC pins, the double-shear strength was τu = 76.5 MPa, 99.7 MPa, and 79.6 MPa for test types I, II, and III, respectively. Compared with MWK–C/SiC pins, the double-shear strength of MWK–N–C/SiC pins all decreased, i.e., 26.7%, 50.8%, and 8% for test types I, II, and III, respectively. The MWK–N–C/SiC composite and pins possessed high interlaminar shear strength and double-shear strength, due to the needled fiber in the thickness direction, low porosity (10–15%), and high composite density (2.0 g/cm3).

In this paper, the effect of the fiber/matrix interface properties on the tensile and fatigue behavior of 2D woven SiC/SiC ceramic-matrix composites (CMCs) is investigated. The relationships between the interface parameters of the fiber/matrix interface debonding energy and interface frictional shear stress in the interface debonding region and the composite tensile and fatigue damage parameters of first matrix cracking stress, matrix cracking density, and fatigue hysteresis-based damage parameters are established. The effects of the fiber/matrix interface properties on the first matrix cracking stress, matrix cracking evolution, first and complete interface debonding stress, fatigue hysteresis dissipated energy, hysteresis modulus, and hysteresis width are analyzed. The experimental first matrix cracking stress, matrix cracking evolution, and fatigue hysteresis loops of SiC/SiC composites are predicted using different interface properties.

Compared with federated avionic architecture, the integrated modular avionic (IMA) system architecture in the aircraft can provide more sophisticated and powerful avionic functionality, and meanwhile, it becomes structurally dynamic, variably interconnected, and highly complex. The traditional approach such as fault tree analysis (FTA) becomes neither convenient nor sufficient in making safety analysis of the IMA system. In order to overcome the limitations, the approach that FTA combines with generalized stochastic petri net (GSPN) is proposed. First, FTA is used to establish the static model for the top level of the IMA system, while GSPN is used to build a dynamic model for each cell system. Finally, the combination model is generated, which is called the FTGPN model. Moreover, the FTGPN model is made safety analysis with the PIPE2 tool. According to the simulation result, corresponding measures are taken to meet the safety requirements of the IMA system.

In this paper, the in-phase thermomechanical fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) have been investigated. The relationships between the thermal cyclic temperatures, fiber/matrix interface shear stress, fiber/matrix interface debonding/sliding and the stress/strain hysteresis loops have been established. The effects of fiber volume fraction, fatigue peak stress, matrix cracking space, fiber/matrix interface debonded energy and thermal cyclic temperature range on the in-phase thermomechanical fatigue hysteresis loops have been analyzed. The in-phase thermomechanical fatigue hysteresis loops of cross-ply SiC/MAS composite have been predicted for different applied cycle number.

In this paper, the SiC/SiC high-pressure turbine twin guide vanes were fabricated using the chemical vapor infiltration (CVI) method. Cyclic thermal shock tests at different target temperatures (i.e., 1400, 1450, and 1480 °C) in a gas environment were conducted to investigate the damage mechanisms and failure modes. During the thermal shock test, large spalling areas appeared on the leading edge and back region. After 400 thermal shock cycles, the spalling area of the coating at the basin and back region of the guide vane was more than 30%, and the whole guide vane turned gray, due to the formation of SiO2. When the thermal shock temperature increased from 1400 to 1450 and 1480 °C, the spalling area of the basin and the back region of the guide vane did not increase significantly, but the delamination occurred at the tenon, upper surface of the guide vane near the trailing edge of the guide vane. Through the X-ray Computed Tomography (XCT) analysis for the guide vanes before and after thermal shock, there was no obvious damage inside of guide vanes. The oxidation of SiC coating and the formation of SiO2 protects the internal fibers from oxidation and damage. Further investigation on the effect of thermal shock on the mechanical properties of SiC/SiC composites should be conducted in the future.