Tensile Properties of Ceramic Matrix Fiber Composites

The mechanical properties of various 2D ceramic matrix fiber composites were characterized by tension testing, using the gripping and alignment techniques development in this work. The woven fabric composites used for the test had the basic combinations of Al₂O₃ Fabric/Al₂O₃, SiC fabric/SiC, and SiC minofilament uniweave fabric/SiC. Tension testing was performed with strain gauge and acoustic emission instrumentation to identify the first-matrix cracking stress and assure a valid alignment. The peak tensile stresses of these laminate composites were about one-third of the flexural strengts. The SiC monofilament uniweave fabric (14 vol%)/SiC composites showed a relatively high peak stress of 370 MPa in tension testing.     

纤维增强陶瓷基复合材料概述

连续纤维增强陶瓷基复合材料是最有前途的高温结构材料之一,以其优异的高韧性、高强度得到世界各国的高度重视。综述了纤维增韧陶瓷基复合材料的选材原则、主要的增韧机理、制备方法以及目前主要的界面改性方法。得到以下结论：纤维的选择必须满足工作环境的要求,纤维与基体之间要在热力学上相匹配;主要的增韧机理为载荷转移、微裂纹增韧、裂纹偏转、纤维脱粘和纤维拔出;复合材料的主要制备方法是热压法、CVI法和聚合物浸渍裂解法;目前最有效的界面改性方法是纤维表面涂层。用氧化物纤维作为增韧体,研究更加简单适用于大规模生产的制备方法,研究更加简单的涂层工艺是今后研究纤维增强陶瓷基复合材料的重点。     

短切碳纤维增强LAS玻璃—陶瓷的研究

研究了短切碳纤维增强ＬＡＳ玻璃－陶瓷基复合材料的制备工艺及纤维含量，热压工艺对其强韧性的影响，获得了短切碳纤维均匀分散并单向排列的复合材料，当纤维体积分数为１％左右时，材料强度和断裂韧性分别达到４３０ＭＰａ和８．８ＭＰａ．ｍ＾１／２。用光学显微镜和扫描电子显微镜观察了复合材料中短切碳纤维的分布状态和断口形貌。     

SiC短纤维增强SiC-BN复合陶瓷

采用原位合成的方法设计并制备了SiC短纤维增强的SiC—BN复合陶瓷。经理论计算及实验证明，在相对较低的温度(1700℃)下即可成功实现预期的原位反应，生成了细小均匀的微米级SiC和BN颗粒，并研究了纤维和BN含量对复合陶瓷组织结构和力学性能的影响。     

陶瓷基复合材料的界面相容性研究

有关陶瓷基复合材料（CMC）的界面问题已经得到广泛的重视。为了使材料达到一个很好的刚性，在纤维与基体之间保持尽量小的界面作用力对于陶瓷纤维增强Si-C-O复合材料是非常重要的。在纤维界面上涂层有利于减小它们之间相互作用，涂层处理后的Si-C-O复合材料的弯曲强度比一般无涂层的复合材料高5倍。在介质涂层、基体、以及涂层与纤维间的三相物质中避免化学反应的发生。目前，可利用化学相容性的原理对涂层纤维进行选择。     

Frictional Stress Evaluation along the Fiber-Matrix Interface in Ceramic Matrix Composites

A finite element algorithm, developed for frictional comact problems, has been used to evaluate the shear stresses along the fiber-matrix interface in a ceramic composite and the load point fiber displacements dining fiber compression. The induced peak shear stress and the shear stress gradient were found to increase with increasing coefficients of friction. Calculated fiber displacements asymptotically decayed to the perfectly bonded condition as the coefficient of friction was increased. The computed average interfacial shear stress showed remarkable agreement with recent experimental findings hi the SiC-LAS system.     

Interface Debonding and Fiber Cracking in Brittle Matrix Composites

Analyses of debonding along interfaces and of the kinking of interface cracks into a fiber have been used to define the role of debonding in fiber-reinforced, brittle matrix composites. The results reveal that, for fibers aligned with the tensile stress axis, debonding requires an interface fracture energy, Γ_i, less than about one-fourth that for the fiber, Γ_f. Further-more, once this condition is satisfied, it is shown that fiber failure does not normally occur by deflection of the debond through the fiber. Instead, fiber failure is governed by weakest-link statistics. The debonding of fibers inclined to the stress axis occurs more readily, such that debonds at acutely inclined fibers can deflect into the fiber, whereupon the failure of fibers is dominated by their toughness.     

纤维增强聚合物基复合材料的界面研究进展

本文较系统的综述了国内外增强树脂用玻璃纤维、碳纤维及芳纶纤维表面处理的方法，对各种改性技术的特点进行了评述，并指出了其进一步的发展趋势。     

纤维增强陶瓷基复合材料界面及增韧机制的进展

陶瓷基复合材料以其优异的耐高温、热稳定性好、耐磨损等性能,在高技术领域和航空航天领域有重要应用。界面在纤维和陶瓷基体之间起着决定性的作用,复合材料的界面相是纤维与基体连接的纽带,也是应力及其它信息传递的桥梁。本文分别从不同复合方式、复合材料的界面研究及纤维增强基体的增韧机制和界面的力学性能等方面进行了综述。     

Microcomposite Test Procedure for Evaluating the Interface Properties of Ceramic Matrix Composites

A microcomposite test procedure for evaluating the constituent properties of CMCs produced by chemical vapor infiltration is described. The analysis and experimental results demonstrate that the interface sliding resistance t_o can be obtained from the unload/reload hysteresis, after one (or more) matrix crack has been induced. The nonlinear strain can also be used to provide an independent determination of t_o, as well as give values for the misfit strain and the interface debond energy. Results obtained on SiC/C/SiC and SiC/BN/SiC materials are evaluated.     

玻璃纤维增强聚合物基复合材料的表面研究进展

文章较系统的综述了国内外增强树脂用玻璃纤维表面处理的方法,包括用偶联剂处理、等离子体表面处理、在玻璃纤维的表面接枝处理以及其它处理方法。对各种改性技术的特点进行了评述。并指出了其进一步的发展趋势。     

连续碳化硅纤维增强碳化硅陶瓷基复合材料研究进展

碳化硅纤维增强碳化硅陶瓷基(SiC/SiC)复合材料具有轻质、耐高温、抗氧化的优异特性,在航空领域,如航空发动机的热端构件、高温结构功能一体化构件,航天及空天飞行器热防护结构部件、动力系统热端部件等领域具有广泛的应用前景,受到美国、欧洲、日本等国研究人员的广泛关注。本文从组成、制备工艺、加工工艺和考核应用等方面,综述了SiC/SiC复合材料的国内外研究进展,并指出了目前面临的问题和机遇。     

纤维增强热塑性树脂基复合材料界面问题研究

阐述了结晶型和非结晶型热塑性树脂基复合材料界面问题的研究现状和趋势,表明界面相互作用力的强弱决定着高分子复合材料的性能和应用,通过控制界面层结构来调整界面性能,以适应不同环境的需要,是纤维增强聚合物基复合材料的研究目的之一。指出由于界面相的复杂性,有关界面理论和界面优化的研究意义重大。     

连续纤维增强陶瓷基复合材料合成技术及发展趋势

作为结构材料,陶瓷具有耐高温能力强、抗氧化能力强、硬度大、耐化学腐蚀等优点,然而呈现脆性,不能承受剧烈的机械冲击和热冲击等缺点,严重影响了它的实际应用。为此,人们通过采用连续纤维增韧方法改进其特性,研发出连续纤维增强陶瓷基复合材料。本文综述了陶瓷基连续纤维增强复合材料的制备方法,分析了各种工艺的优缺点。在总结了现阶段连续纤维增强复合材料研究中存在的问题基础上,提出了今后连续纤维增强复合材料的主要研究方向。     

Lanxide陶瓷基复合材料的研究进展

Lanxide熔融金属直接氧化技术是一种新型的复合材料制备技术,通过用预制体(颗粒、晶须、纤维等)增强所制备的复合材料具有高的体积稳定性、断裂韧性和强度,是目前材料科学领域的热点之一.本文就Lanxide技术及陶瓷基复合材料近年来的最新发展进行了概述.     

连续纤维增强陶瓷复合材料的制造,性能及应用

本文介绍陶瓷纤维增强材料,陶瓷增强陶瓷基体复合材料的制法和性能及其潜在的工业应用。     

裂解碳包覆对SiC纳米纤维增强SiC陶瓷基复合材料性能的影响

以SiC纳米纤维(SiC_nf)为增强体,通过化学气相沉积在SiC纳米纤维表面沉积裂解碳(PyC)包覆层,并与SiC粉体、Al₂O₃-Y₂O₃烧结助剂共混制备陶瓷素坯,采用热压烧结工艺制备质量分数为10%的SiC纳米纤维增强SiC陶瓷基(SiC_nf/SiC)复合材料。研究了PyC包覆层沉积时间对SiC_nf/SiC陶瓷基复合材料的致密度、断裂面微观形貌和力学性能的影响。结果表明:在1 100 ℃下沉积60 min制备的PyC包覆层厚度为10 nm,且为结晶度较好的层状石墨结构;相比于纤维表面无包覆层的复合材料,复合材料的断裂韧性提高了35%,达到最大值(19.35±1.17) MPa·m^1/2,抗弯强度为(375.5±8.5) MPa,致密度为96.68%。复合材料的断裂截面可见部分纳米纤维拔出现象,但SiC_nf/SiC陶瓷基复合材料界面结合仍较强,纳米纤维拔出短,表现为脆性断裂。     

Interface Design for Oxidation-Resistant Ceramic Composites

Fiber-reinforced ceramic composites achieve high toughness through distributed damage mechanisms. These mechanisms are dependent on matrix cracks deflecting into fiber/matrix interfacial debonding cracks. Oxidation resistance of the fiber coatings often used to enable crack deflection is an important limitation for long-term use in many applications. Research on alternative, mostly oxide, coatings for oxide and non-oxide composites is reviewed. Processing issues, such as fiber coatings and fiber strength degradation, are discussed. Mechanics work related to design of crack deflecting coatings is also reviewed, and implications on the design of coatings and of composite systems using alternative coatings are discussed. Potential topics for further research are identified.     

Ceramic Composites with Multilayer Interface Coatings

Silicon carbide matrix composites have been fabricated from either ceramic-grade Nicalon^TM or Hi-Nicalon^TM fibers coated with an interface material consisting of six alternating carbon and silicon carbide layers. Initial efforts involved the use of chemical vapor infiltration to produce minicomposites (single tows of fibers). In subsequent work, forced-flow thermal-gradient chemical vapor infiltration was used to produce a single composite plate with a multilayer interface from ceramic-grade Nicalon fabric and two plates from Hi-Nicalon fabric, one with a single carbon layer and one with a multilayer interface. Tensile testing of the minicomposites and of specimens cut from the plates revealed typical composite behavior and strengths for the as-processed samples. Exposure of tensile specimens to 950°C air for 100 h resulted in large losses in strength and strain tolerance regardless of the interface coating. The results demonstrate that forced-flow thermal-gradient chemical vapor infiltration can be used to prepare multilayer interface material. The results also verified that relatively thick (>100 nm) single or multiple carbon layers are susceptible to oxidation that causes the loss of composite properties.