陶瓷基复合材料微观结构设计

把弹性力学和断裂力学应用到颗粒弥散复相陶瓷的微观热应力分析中，对弥散相颗粒尺寸和体积分数的临界值进行了推导，并提出了颗粒弥散陶瓷微观结构及材质设计的一般性原则。     

陶瓷基复合材料微观结构设计

把弹性力学和断裂力学应用到颗粒弥散复相陶瓷的微观热应力分析中，对弥散相颗就尺寸和体积分数的临界值进行了推导，并提出了颗粒弥散陶瓷微观结构及材质设计的一艉性原则。     

陶瓷基复相材料的非相变增韧机制

本文讨论了脆性陶瓷基复相材料不同于其它韧性基体复合材料的特点,较为系统的论述了颗粒弥散复相陶瓷材料的主要非相变增韧机制,为高韧性新型复相陶瓷材料研究开发提供理论参考。     

Si3N4／SiCp复相陶瓷材料的研究进展

概述了ＳｉＣ颗粒弥散强化Ｓｉ３Ｎ４陶瓷的研究近况,着重讨论了ＳｉＣ粒子的数量和尺寸对Ｓｉ３Ｎ４／ＳｉＣｐ复相陶瓷材料显微结构和力学性能的影响,并简要介绍了Ｓｉ３Ｎ４／ＳｉＣｐ复相陶瓷材料的烧结机理和ＳｉＣｐ的掺入对材料可烧结性的影响。     

颗粒增韧陶瓷裂纹扩展微观过程

对于第二相颗粒增韧的复相陶瓷，颗粒热膨胀系数ａｐ与基体热膨胀系数ａｍ之间的匹配关系是决定增韧效果的主要因素。当两相弹性模量相当，颗粒粒径小于应力诱导微开裂的粒径，且ａｐ〉ａｍ时，残余热应力场的存在将会使扩展的裂纹在颗粒周围基体中产生较大的裂纹偏转，由此产生明显的增韧效果；而当ａｐ〈ａｍ时，扩展的裂纹将首先达到两相的界面，此时裂纹有可能沿两相界面偏转，也有可能穿过颗粒，这取决于颗粒的表面能、粒径、形     

颗粒增强复相陶瓷残余应力和增韧机制分析

对颗粒增强复相陶瓷在增强颗粒密排分布条件下材料内残余应力的大小和分布进行了理论分析，探讨了αｐ〉αｍ和αｐ〈αｍ情况下的强化增韧机制以及在这两种情况下所存在的增韧机制的差别。研究结果表明，残余应力不仅与基体和颗粒的物理参量有关，而且还与所在点位置和增强颗粒体积含量有关。颗粒增强复相陶瓷在αｐ〉αｍ和αｐ〈αｍ情况下，都可能达到强化增韧的效果。在αｐ〈αｍ情况下，主要增韧机制是裂纹偏转和残余应力场强     

先进复相陶瓷的研究现状和展望（Ⅱ）———高组元陶瓷复合材料的研究进展

本文综述了目前国内外多元系复相陶瓷的研究进展，复合范围主要包括相变增韧，晶须和颗粒弥散强化之间的两两混合以发挥协同效应     

Si_3N_4/BAS复相陶瓷材料制备及其性能EI北大核心CSCD

采用新型冷冻胶凝陶瓷成型技术制备高性能Si_3N_4/BAS复相陶瓷透波材料,对Si_3N_4/BAS复相陶瓷材料烧结体成分、力学性能、微观形貌、电性能及抗热震性等进行研究。结果表明:坯体成型收缩率小于1%,在温度升到1 300℃高温时,Si_3N_4/BAS复相陶瓷烧结体弯曲强度280 MPa,弹性模量为90 GPa,介电常数变化率仅为6%。该复相陶瓷材料具有良好的抗热震性能及可加工性,BAS陶瓷玻璃相高温高黏度特性对Si_3N_4/BAS复相陶瓷材料抗热震是一种热应力缓释方式。     

弥散SiC颗粒增韧Al_2O_3基陶瓷的增韧机制分析

通过对SiC Al2 O3 陶瓷材料内部残余应力的分析 ,根据Griffith微裂纹理论 ,从多个角度分析了弥散SiC颗粒对Al2 O3 材料的增韧机制     

弥散SiC颗粒增韧Al2O3基陶瓷的增韧机制分析

通过对SiC-Al2O3陶瓷材料内部残余应力的分析,根据Griffith微裂纹理论,从多个角度分析了弥散SiC颗粒对Al2O3材料的增韧机制.     

A theoretical study of the effect of an interfacial layer on the properties of composites

A theoretical analysis using finite element methods has been applied to oriented short-fiber composites and spherical particle composites in order to predict the influence of a finite layer at the interface on mechanical properties. In this study the interfacial layer has been modeled by assuming that a layer surrounds the interface and that this layer has a modulus of elasticity different than both the fiber and the matrix. The stress distribution near the interface has been determined as a function of the elastic constants of the interface layer and the interface layer volume fraction. This analysis has also been performed for two volume fractions of fibers and two fiber length to diameter ratios. From this stress distribution, the composite modulus and toughness have been determined as a function of interface modulus. It is theoretically shown that the toughness, measured by amount of strain energy absorbed, can be maximized by controlling the interface modulus. Furthermore, recent experimental results appear to verify the theory.     

Electrochemical polarization phenomena at the interface of two immiscible electrolyte solutions

The faradaic and non-faradaic processes taking place at the interface of two immiscible electrolyte solutions have been compared with analogous processes occurring at the interface metal-electrolyte solution. For the former interface conditions have been stated for obtaining suitable current-potential characteristics. As methods of investigation, cyclic voltammetry, chronopotentiometry and polarography with an electrolyte dropping electrode have been used. For the simple ion transfer across the interface, examples of reversible and irreversible processes have been described. In the presence of ionophores (valinomycin and a crown polyether) the transfer of alkali metal ions is facilitated. This phenomenon has been exploited for determination of stability constants. The interface of two immiscible electrolyte solutions may be used as a model of the surface of a biological membrane.     

Evaluation of the Tensile Interface Strength in Brittle-Matrix Composite Systems

Two test methods for determining the tensile (normal) interface bond strength in brittle-matrix composites have been described: one geometry is the cruciform bend specimen, and the other is the embedded fiber specimen. Both specimens have the characteristic that free edge debonding is avoided, so that valid interface strength data can be obtained from the knee in the stress-strain curve. The techniques are applied to a Sigma SiC/7040 glass composite, and a bond strength of ∼5 MPa has been obtained. The method of analysis is described. Normal interface separation has been observed at or very close to the SiC/carbon (primarily graphite) interface of the Sigma fiber and is consistent with the weak orientation of the graphitic layers. Two examples of interface separation are cited in the as-fabricated composite, to show the application and validation of the test results. In one instance, tensile interface separation has been observed next to existing voids, and in the other instance, interface separation has occurred near radial matrix cracks. Analyses show that the debonds are consistent with the low normal strength of the interface.     

Influence of the roughness of aggregate surface on the interface bond strength

An experimental investigation on the bond strength of the interface between mortar and aggregate is reported. Composite compact specimens were used for applying Mode I and Mode II loading effects. The influence of the type of mortar and type of aggregate and its roughness on the bond strength of the interface has been studied. It has been observed that the bond strength of the interface in tension is significantly low, though the mortars exhibited higher strength. The highest tensile bond strength values have been observed with rough concrete surface with M-13 mortar. The bond strength of the interface in Mode I load depends on the type of aggregate surface and its roughness, and the type of mortar. The bond strength of the interface between mortar M-13 cast against rough concrete in direct tension seems to be about one third of the strength of the mortar. However, it is about 1/20th to 1/10th with the mortar M-12 in sandwiched composite specimens. The bond strength of the interface in shear (Mode II) significantly increases as the roughness and the phase angle of the aggregate surface increase. The strength of mortar on the interface bond strength has been very significant. The sandwiched composite specimens show relatively low bond strength in Mode I loading. The behavior of the interface in both Mode I and Mode II loading effects has been brittle, indicating catastrophic failure.     

The interface between glass and carbon fibers and thermosetting polymers

The interface between the fibers and the polymer matrix controls the properties of fiber composites and has been the subject of much study. Recently, special techniques have been developed for single fiber pull-out experiments on production fibers, which make it possible to obtain data on the frictional forces which govern sliding after the interface has fractured, as well as the adhesion strength of the interface. Tests on glass in polyester and epoxy resins show that the work of fracture of the interface is much smaller than that of the resin, and that the shrinkage pressures of these matrices, when fully postcured, are approximately the same (about 20 MPa). Coefficients of friction at the interface are 0.6 for the polyester and 1.0 to 1.6 for the epoxy. The carbon-epoxy interface yields at shear stresses as high as 60 MPa, instead of fracturing, and the coefficient of friction during sliding is about 0.4.     

Tension-tension fatigue behavior of unidirectional SiC/Si3N4 composite with strong and weak interface bonding at room temperature

In this paper, the tension-tension fatigue behavior of unidirectional SiC/Si₃N₄ ceramic-matrix composite with strong and weak interface bonding at room temperature has been investigated using a micromechanical approach. The hysteresis loops models considering different interface slip cases have been developed to establish the relationships between fatigue hysteresis loops, hysteresis dissipated energy, hysteresis modulus, and the interface shear stress. The damage evolution process under tension-tension fatigue loading has been analyzed using hysteresis loops. By comparing experimental fatigue hysteresis dissipated energy with theoretical computational values, the interface shear stresses of SiC/Si₃N₄ composite with weak and strong interface bonding were obtained for different cycle numbers. The fatigue life S‒N curves and broken fibers fraction versus cycle number curves corresponding to different fatigue peak stresses have been predicted. For SiC/Si₃N₄ with strong interface bonding, the fatigue limit stress approaches to 75% tensile strength, which is much higher than that of composite with weak interface bonding, i.e., 58% tensile strength, due to the higher interface shear stress degradation rate for weak bonding interface.     

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

ABSTRACT

In 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.     

固井二界面定量评价新方法研究

本文针对套管井中第二界面定量评价的问题,首先开展了套管井中地层波的影响因素的研究,为定量评价第二界面的胶结质量奠定了基础;接着,通过有效确定地层波到达时间,以及地层波信号提取及能量计算,并在充分考虑地层岩性影响的基础上修订了传统的第二界面胶结指数公式,建立了一套完整的定量评价固井二界面胶结质量的新方法;最后通过实际资料处理与评价,证明所提出的定量评价固井二界面胶结质量方法取得了满意的效果。     

The effect of interfacial microstructure on the interfacial strength of glass fiber/polypropylene resin composites

In this study, a new method to form resin droplets on fibers has been developed, and samples for the single fiber pull-out test were prepared using this method. The effects of microstructure of polypropylene (PP) resin and the microstructure of interface between the glass fiber and PP resin on the interfacial strength have been investigated. In addition, the influence of the microstructure of the interface on the interfacial strength of glass fiberreinforced PP composites have been discussed. It has been found that in the pull-out test, the transcrystallinity formed at the interface between the glass fiber and PP resin improved the interfacial strength when no spherulites developed in the PP matrix. On the other hand, it has been found that when the spherulites were well developed in the PP matrix, the transcrystallinity formed at the interface reduced the interfacial strength. Finally, rapid cooling has been shown to improve the interfacial strength between the fiber and resin in the crystalline polymer matrix composites. © 1994 John Wiley & Sons, Inc.     

Surface and interface analysis of nanostructured porous silicon layers fabricated at low temperatures from highly doped silicon substrate: application in optical filters

The influence of low temperature of the electrolyte on the surface and interface of porous silicon and its application in optical devices has been studied. Porous Si–bulk Si interface profile was observed by means of the high resolution SEM images. At low temperatures, a decrease in the interface roughness and an increase in the pore size has been observed. These results were used to fabricate optical filters for UV and visible regions at low temperatures. As compared to the filters fabricated at room temperature an increased optical response is reported for the filters formed at low temperature.