SiC纤维补强微晶玻璃基复合材料的界面结合

本文通过ＳｉＣ纤维对ＬＣＡＳ（Ｌｉ２Ｏ－ＣａＯ－Ａｌ２Ｏ３－ＳｉＯ２）和ＭＡＳ（ＭｇＯ－Ａｌ２Ｏ３－ＳｉＯ２）微晶玻璃的补强，观察和分析了在不同复合系统中纤维与基体的界面结合。在ＳｉＣ纤维／ＬＣＡＳ微晶玻璃复合系统中，发现纤维与基体之间有一中间界面层，它主要是在复合材料的烧结过程中通过扩散形成，并且于１２００℃时在界面上形成富Ｃ层。ＳｉＣ纤维／ＭＡＳ微晶玻璃基复合材料由于在烧结过程中有化学反应发生     

纤维涂层对复合材料力学性能的影响

对于ＳｉＣ纤维／ＭＡＳ微晶玻璃复合系统，发现在烧结温度下，纤维和基体之间有较严重的化学反应发生，界面结合强，力学性能较差．通过对ＮｉｃａｌｏｎＳｉＣ纤维加涂层，发现Ｎｂ２Ｏ５和ｃ涂层对复合材料的界面结合改善不大，而ＬＣＡＳ晶玻璃涂层能使纤维和基体间的界面结合明显减弱，力学性能大幅度提高，室温抗折强度和断裂韧性分别达３２７ＭＰａ和１３．９ＭＰａ·ｍ１／２．     

SiC纤维／LAS复合材料的TG－DTA－MS研究

本文首次用ＴＧ－ＤＴＡ－ＭＳ联用技术对ＳｉＣ纤维／ＬＡＳ微晶玻璃复合材料的热分解过程、机制及其与晶化的关系进行了研究。提出了该复合材料界面形成碳层的热力学和质谱分析判别依据，并对晶化前后的复合材料的热分解行为作了实验对比和理论分析。     

多向细编碳／碳复合材料界面力学性能测试与表征

本文用自制装置研究了多向细编Ｃ／Ｃ复合材料纤维束性能，分析了工艺过程的影响。同时用界面微脱粘实验技术研究了Ｃ／Ｃ复合材料界面性能，给出了相应的理论模型和界面应力分布，提出了由界面脱粘力，纤维、基体和复合材料性能表征界面剪切强度的方法，为Ｃ／Ｃ复合材料优化设计提供了定量参数。结果表明：织物结构、织物编织工艺以及织物／基体复合对纤维的强度影响很大，降为原始纤维的２０％左右，对模量影响小。不同界面层次，纤维／基体的界面结合情况和界面剪切强度不同，Ｚ向纤维束中纤维／基体结合好，具有最高的结合强度，ＳＥＭ观察证实有大量基体碳在纤维上枝联。     

AIN和B对热压烧结Cf/SiC复合材料性能的影响

研究了烧结助剂ＡＩＮ 和Ｂ对Ｃｆ／ＳｉＣ复合材料力学性能的影响。结果表明：Ｂ含量较低时（小于０．５ｗ ｔ％ ）,Ｂ的增加能有效地提高复合材料的抗弯强度与断裂韧性,继续增加Ｂ的用量至１ｗ ｔ％ ,虽能大幅度提高复合材料的强度,但使复合材料的断裂韧性大大降低。ＡＩＮ 与ＳｉＣ高温反应形成固溶体,能起到强化和细化基体ＳｉＣ晶粒以及改善ＳｉＣ晶界结构的作用,但对复合材料内纤维与基体间界面的结合影响较小,因此与Ｂ的作用相比,ＡＩＮ 对复合材料密度和力学性能的影响较小。烧结助剂为５ｗ ｔ％ ＡＩＮ－０．５ｗ ｔ％ Ｂ,经１８５０℃和２５ＭＰａ 热压烧结后的Ｃｆ／ＳｉＣ复合材料具有较佳的综合力学性能,其抗弯强度与断裂韧性值分别为５２６．６ＭＰａ 和１７．１４ＭＰａ·ｍ １／２。     

碳化硅纤维增强铝基复合材料的界面组织研究EI

本文利用透射电子显微术（ＴＥＭ）和微区能谱分析（ＥＤＸ）对化学气相沉积碳化硅纤维增强ＬＤ２铝合金的界面结构进行了研究，并对显微组织与性能的关系进行了讨论。结果发现，用热压扩散工艺生产的ＳｉＣ／Ａｌ复合材料，其基体与ＳｉＣ纤维结合良好。界面处有棒状相Ａｌ＿４Ｃ＿３生成（该相是菱形结构，对纤维强度有较大破坏作用），且存在镁元素富集。     

SiC（CVD）／Al复合材料界面剪切强度的测试

本文利用声发射技术，成功地测出ＳｉＣ（ＣＶＤ）单纤维增强Ａｌ基复合材料在拉伸过程中纤维的平均断裂长度，并由萃取纤维的方法加以验证。再用微观力学模型，计算出纤维与基体之间的界面剪切强度。     

界面结构对SiCf／Al复合材料性能和声发射行为的影响

运用高分辨场发射扫描电镜（ＦＥ－ＳＥＭ）和声发射（ＡＥ）测试研究了ＳｉＣ纤维铝基复合材料的不同界面组成和界面产物及其对复合材料性能和ＡＥ行为的影响发现富碳自理的ＳｉＣｆ／Ａｌ生成Ａｌ４Ｃ３脆性界面,在伸过程中界面脆断产生许多中幅ＡＥ信号,而富ＳｉＯ２处理的ＳｉＣｆ／Ａｌ生成韧工较高的富氧产物,界面强度较高,在形变过程中不易发生界面断裂,不产生中幅ＡＥ信号。     

LCMAS微晶玻璃／Y－TZP复相材料

本工作对ＬＣＭＡＳ微晶玻璃／Ｙ－ＴＺＰ复相材料在不同的烧结温度下所出现的晶相进行了研究，发现材料在烧结温度下，Ｙ－ＴＺＰ中的ＺｒＯ２与微晶玻璃中的ＳｉＯ２发生化学反应生成锆英石（ＺｒＯ２·ＳｉＯ２），少量Ｙ－ＴＺＰ的加入起不到相变增初作用．由于Ｙ－ＴＺＰ起到微晶玻璃晶核剂的作用，仍能使材料的抗折强度和断裂韧性得到大幅度的提高．当Ｙ－ＴＺＰ含量为９５ｗｔ％时，复相材料的抗折强度和断裂韧性分别为６３１ＭＰａ和８．４ＭＰａ．ｍ１／２．     

SiCw＋B4Cp／MB15镁基复合材料力学性能与微观结构

对真空反压浸渍方法制备的挤压态ＳｉＣＷ＋Ｂ４ＣＰ／ＭＢ１５镁基复合材料及基体合金进行了一系列的力学性能测试，并用ＳＥＭ观察增强剂分布与断口形貌，用ＴＥＭ和ＥＤＳ方法对复合材料的界面结构进行分析。研究结果表明，上述复合材料同基体相比有更高的强度、弹性模量和比强度、比弹性模量。深浸蚀ＳＥＭ相分析表明均匀排布的晶须、颗粒起到很好的增强效果。复合材料的断口有晶须露头与韧窝存在，该复合材料具有一定的韧性；并在ＳｉＣ／ＭＢ１５界面上发现Ｚｎ析出相。     

Fracture behaviour of SiC fibre-reinforced nitrogen glass matrix composites

Both Nicalon and Hi-Nicalon SiC fibre-reinforced nitrogen glass composites were prepared by slurry infiltration and hot-pressing, and the interfacial features, fracture behaviour and mechanical properties of these composites were investigated. It was found that the interfacial characteristics were mainly dictated by the thermal expansion properties of the matrix and the type of SiC fibre. Yttrium sialon glass has a higher thermal expansion coefficient than SiC fibres, so a radial compressive stress on the fibre due to thermal mismatch caused a larger interfacial frictional stress between fibre and matrix. As a result, the composite failed in a brittle manner with no effective strengthening and toughening. Strong reaction between the Hi-Nicalon SiC fibre and matrix also resulted in relatively poor performance of these composites. In contrast, lithium sialon glass provided a matrix for these composites with significantly improved mechanical properties.     

Effects of thermal cycling on thermal expansionand mechanical properties of SiC fibre-reinforced reaction-bonded Si3N4 composites

Thermal expansion curves for SiC fibre-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 °C in nitrogen and in oxygen. The effects of fibre/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fibre direction were between the measured curves for the strongly- and weakly-bonded composites, but those normal to the fibre direction for both bonding cases were similar to that of the unreinforced RBSN. Thermal cycling in nitrogen for both bonding cases resulted in no net dimensional changes at room temperature and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly-bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fibre and RBSN matrix due to oxidation of the carbon-rich fibre surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites. This revised version was published online in November 2006 with corrections to the Cover Date.     

Finite element analysis of the stress distribution in a thermally and transversely loaded Ti–6Al–4V/SiC fibre composite

The load transfer between fibre and matrix in a metal matrix composite (MMC) depends on the properties and conditions of the fibre/matrix interfacial region. The objective of this investigation is to gain a better understanding of the stresses generated within a continuously reinforced MMC, particularly at this interface. Finite element analysis is used to investigate the effect of thermal and transverse mechanical loading on the SiC/Ti–6Al–4V composite system. The effect on the stress field of a carbon coating on the SiC fibres is also investigated. The results indicate that the interfacial region affects the stress distribution, with the presence of the carbon coating significantly altering the stress profiles generated. It is also found that the residual stresses generated as a result of cooling down the composite from processing temperature, has a marked effect on the stress profile and the behaviour of the composite when subsequent mechanical loading is applied.     

Interfacial characterization of Nicalon SiC fibre reinforced oxynitride glass matrix composites

Nicalon SiC and Hi-Nicalon SiC fibre oxynitride glass and glass–ceramic composites were prepared and the interface between the fibres and matrix characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectroscopy. It was found that the formation and thicknesses of interfacial layers were primarily determined by the type of fibre reinforcement, but the role of these interfaces in influencing composite properties was dependent on the thermal properties of the matrix. For Nicalon SiC composites, the carbon-rich layer did not promote fibre debonding and toughening unless the matrix had a smaller thermal expansion coefficient than the fibres. For Hi-Nicalon SiC composites, the absence of oxygen in the fibre significantly encouraged chemical reaction between fibre and matrix, resulting in no strengthening or toughening. This revised version was published online in November 2006 with corrections to the Cover Date.     

Development and properties of a SiC fibre-reinforced magnesium aluminosilicate glass-ceramic matrix composite

The preparation of a magnesium aluminosilicate glass-ceramic matrix composite having an approximately matched thermal expansion coefficient to the silicon carbide fibre reinforcement is described. Data are presented on the process conditions necessary to produce a composite with matched thermal expansion coefficients, the strength and work of fracture of the composite at ambient temperature, and also the effect of temperature on the mechanical properties.     

Effect of heat treatment in air on the structure and properties of barium osumilite reinforced with Nicalon fibres

Microstructural studies have been carried out on glass-ceramic matrix composites, consisting of barium osumilite reinforced with Nicalon fibres, which have been subjected to heat treatment in air in the range 600–1100 °C. Parallel studies have involved the measurement of the friction stress between fibre and matrix and the flexural strength of the composite. The matrix was shown to consist of barium osumilite, hexacelsian, mullite and a silica-rich glass, the thermal mismatch of these different phases leading to the development of appreciable strains. Whilst high-temperature treatments caused the formation of voids due to flow of the glassy phase, the major factor controlling the mechanical properties of the composite was the fibre/matrix interface. A change in microstructure, from a weak carbon-rich interface to one where the fibre and matrix were strongly bonded together by a silica layer, was thus reflected in an increase in the interfacial friction stress and a change in fracture behaviour from one showing fibre pull-out and delamination to one with brittle characteristics.     

SiC纤维/LAS复合材料的TG-DTA-MS研究

本文首次用TG-DTA-MS联用技术对SiC纤维/LAS微晶玻璃复合材料的热分解过程、机制及其与晶化的关系进行了研究。提出了该复合材料界面形成碳层的热力学和质谱分析判别依据,并对晶化前后的复合材料的热分解行为作了实验对比和理论分析。      

Fabrication and properties of SiC fibre-reinforced Li2O·Al2O3·6SiO2 glass-ceramic composites

Ta₂O₅, Nb₂O₅ and TiO₂ were used separately as additives to a Li₂O·Al₂O₃·6SiO₂ glass-ceramic composition, to act as nucleating dopants and to aid the formation of an interfacial carbide layer (TaC and NbC) between the fibre and matrix in SiC fibre uniaxially reinforced glass-ceramic composites, The composites exhibited high modulus of rupture (>800 MPa) and fracture toughness (K _IC > 15 MPam^1/2). The interfacial amorphous carbon rich layer and carbide layer were responsible for lowered interfacial shear strength but permitted high composite fracture toughness. The composite with the TiO₂ additive in the matrix showed a lower flexural strength (<500MPa) and a smaller K _IC (-11 MPam^1/2) which resulted from the high interfacial shear strength between the SiC fibre and the matrix due to the formation of the interfacial TiC layer.     

A novel microbond bundle pullout technique to evaluate the interfacial properties of fibre-reinforced plastic composites

The interfacial properties of the fibre composite systems decide the overall usability of a composite in simple and complex shapes, as they are the deciding factors in determination of the mechanical properties, structural properties and above all a complete understanding of the reliability of composite systems. In the present investigation, the interfacial properties of carbon fibre/epoxy composites viz., matrix shrinkage pressure, interfacial frictional stress, interfacial shear stress and coefficient of friction were evaluated through a novel microbond bundle pullout test. This test is different from the single fibre pull out, fibre fragmentation or the fibre push in test. Based on some of the physical principles involving the single fibre microbond pullout test, like the contact angle of the microbond matrix drop with the fibre surface, the surface tension/energy of the two surfaces before and after adhesion and the interfacial fibre/matrix chemistry, this is simple to perform and statistically averaged mesomechanical test is also easy to evaluate and is shown to be a test method that enables a conservative prediction of the laminate level or macromechanical shear properties of fibre composite systems. This test demonstrates the validity of the mesomechanical tests that are more relevant to the macromechanical tests than the micromechanical tests. Fractography carried out to corroborate the observed mechanical properties with the fracture features is also reported. The general advantages of the mesomechanical interfacial tests over those based on micromechanical assumptions is also discussed along with some common limitations.