焦炭颗粒增强沥青基炭复合材料的组织结构

利用模压半炭化成型工艺,在大气环境下制备了焦炭颗粒增强的沥青基炭复合材料,并借助光学显微镜和扫描电镜对其微观组织和断口形貌进行了观察.结果表明:根据焦炭颗粒增强沥青基炭复合材料的原料结构和制备工艺,利用光学显微镜和扫描电镜,可以清楚地辨别出沥青基炭复合材料中的增强体炭、基体炭和孔隙相三种基本相结构.而且黏结剂炭除了填充增强体炭中的孔隙外,还将每一个增强体颗粒包裹起来,从而在沥青基炭复合材料中形成了一个网络状的连续基体.     

固体浮力材料的等静压成型工艺及性能

以脂环族环氧树脂为基体，空心玻璃微珠(HGMS)为填充材料，分别采用真空辅助等静压成型工艺和模压成型工艺制备了固体浮力材料，并对其性能进行了研究。结果表明：相较于模压成型工艺，采用真空辅助等静压成型工艺制备的固体浮力材料可以有效降低材料密度，提高最大可使用深度。在不断提高HGMS体积分数以得到更低密度深海固体浮力材料时，真空辅助等静压成型工艺制备的固体浮力材料比模压成型工艺制备的固体浮力材料的最大HGMS体积分数可提高1%,密度降低了4.86%,最大可使用深度提高了50%,可达3 000 m。     

沥青种类和焦炭粒度组成对焦炭颗粒增强沥青基炭复合材料性能的影响

采用新型的模压半炭化成型工艺在大气环境下制备出了高密度、低成本的焦炭颗粒增强沥青基炭复合材料（简称CRPCC材料）。研究了煤沥青的种类、沥青焦中添加冶金焦以及焦炭颗粒的粒度组成配比对CRPCC材料的密度和抗压强度的影响。结果表明：煤沥青的软化点高，用其制备的CRPCC材料的密度和抗压强度未必就高；沥青焦中添加一定含量的冶金焦，则可制备出密度和抗压强度更好的CRPCC材料。     

炭纤维增强中间相炭微球制备炭/炭复合材料

以中间相炭微球为炭源,沥青基磨切炭纤维为同质增强相,采用冷模压成型和气氛低温烧结制备出高性能炭/炭复合材料。研究了炭纤维表面处理对界面结合强度的作用机制和改善效果,分析了不同球磨时间下原始粉料的微观形貌。结果表明：炭纤维的添加有利于坯体各向均匀收缩,降低了总体积收缩率,使得复合材料密度下降;同时大幅度提升了复合材料的机械强度;添加10%（质量分数）炭纤维时弯曲强度最高,达到123.5MPa。     

对冷压炭-铜纤维复合材料性能的考察与分析

以冷模压工艺方法,在相同的工艺条件下,制备了一种纯炭材料及６种炭－铜纤维复合材料,测试了该７种材料的电阻率、肖氏硬度、抗压强度、抗折强度、冲击韧性、气孔率及体积密度观察了材料的显微组织结构。分析了影响材料性能的原因,探讨了提高复合材料机械强度的技术措施。     

炭化压力对编织C/C复合材料致密过程及结构的影响

通过浸渍/高压炭化工艺在不同炭化压力下制备了高温煤沥青炭块及沥青基炭/炭（C/C）复合材料,并研究了不同炭化压力环境下对其密度和孔隙的影响.结果表明,随着炭化压力增大,沥青炭体积密度明显增加,孔隙填充效果明显改善;在编织C/C材料的致密过程中,压力越大其孔隙越小,分布越均匀,故产品致密效果越好.     

模压成型环氧树脂/玄武岩纤维复合材料研究

以玄武岩纤维平纹布(BF)为增强体,环氧树脂(EP)为基体,采用模压工艺制备环EP/BF复合材料。研究了加压时机、成型压力、纤维体积含量对复合材料弯曲性能和层间剪切强度(ILSS)的影响,并研究纳米添加剂凹凸棒石/炭(PG/C)对复合材料力学性能及导热性能的影响,运用电子扫描显微镜观察并分析复合材料的断面形貌。结果表明,复合材料的最佳加压时机为凝胶45 min;成型压力和纤维体积含量影响复合材料的弯曲性能和ILSS;在BF体积分数为30%、成型压力为1 MPa条件下,添加纳米添加剂PG/C–0.5(PG/C的质量比为1/0.5)时,复合材料的力学性能最优,相比不含纳米添加剂,复合材料的弯曲强度、弯曲弹性模量及ILSS分别提高4.3%,10.7%和6.4%;添加纳米添加剂PG/C–0.5时,复合材料的导热性能最优,在25℃及100℃下的导热系数为0.28 W/(m·K)和0.31 W/(m·K),相对不含纳米添加剂时分别提高64.7%及41.0%。PG与负载在其表面的炭之间的协同作用促进了复合材料力学性能及导热性能的提高。     

不同工艺碳纤维增强复合材料构件的力学性能

针对碳纤维增强复合材料在电动汽车车身上的应用,分别采用手糊、真空袋压和模压三种成型工艺,设计制备了碳纤维增强复合材料层合板和双帽形管件两种实验样件。对样件进行了单向拉伸和三点弯曲试验,对构件的力学性能、表面质量、微观结构和破坏形式进行了比较,并分析了不同工艺性能存在差异的原因。研究表明:采用模压工艺成型的复合材料结构件气泡少,孔隙率小,表面质量最好;模压成型的层合板拉伸强度比手糊成型的提高了14.39%,管件弯曲强度比手糊成型管件提高了一倍,比真空袋压成型管件提高了47.58%。研究证实模压成型相对于手糊和真空袋压工艺,产品具有较优良的力学性能和一致性,较适合于电动汽车等轻量化结构的成型。     

有机物浸渍/涂敷-固化-碳化法制备膨胀石墨基低密度炭/炭复合材料

在膨胀石墨基炭／炭复合材料研究领域，国内外研究者采用的制备工艺大多为有机物浸渍-固化-碳化法。本文介绍了采用此制备工艺的两种膨胀石墨基低密度炭／炭复合材料的一些研究工作：一种材料为以膨胀石墨基炭／炭低密度复合材料活化后制取块状成型活性炭；另一种为利用膨胀石墨基炭／炭低密度复合材料作为绝热材料。     

沥青基炭复合材料的制备及力学各向异性性质的探讨

采用新型的模压半炭化成型工艺在大气环境下制备出了高密度、低成本的焦炭颗粒增强沥青基炭复合材料（CRPCC）。研究了焦炭颗粒的种类对CRPCC材料的力学各向异性性质的影响。结果表明：由于沥青焦Ⅰ的颗粒形状系条状或棒状，故用其制备的CRPCC材料的力学性能具有明显的各向异性，且各向异性系数高达25％；而沥青焦Ⅱ和冶金焦的颗粒形状为多角形或准球形，故用它们制备的CRPCC材料基本上都是各向同性的。     

短切碳纤维含量对Csf/SiC复合材料力学性能的影响

以Si作为主要烧结助剂,采用热压烧结法制备了短切碳纤维-碳化硅(short carbon fiber reinforced SiC composite,Csf/SiC)复合材料.采用X射线衍射仪、扫描电镜、硬度仪以及力学性能试验机等,研究了Csf含量对所制备材料的结构、组成、形貌及复合材料的弯曲强度、Vickers硬度和断裂韧性的影响.结果表明:采用热压法能制备出致密且Csf分布均匀的Csf/SiC复合材料.Csf/SiC复合材料的弯曲强度随Csf含量增加先增大后减小,含15%(体积分数,下同)Csf的Csf/SiC样品强度最高,达到466MPa,并且Csf含量小于30%的Csf/SiC样品强度高于无纤维SiC材料.材料的Vickers硬度随Csf含量增加而降低.Csf/SiC样品的断裂韧性随Csf含量增加而逐渐增大,Csf含量为53%时,达到最大为5.5MPa·m1/2,与无纤维SiC样品相比,增加近2倍.     

ZrB2含量对LaB6-ZrB2复合材料性能的影响

采用碳热还原法合成了不同ZrB2含量的LaB6-ZrB2复合粉末。通过热压烧结法制备了相应的复合材料,其性能测试结果表明：随着ZrB2含量的增加,LaB6-ZrB2复合材料的硬度和弯曲强度均随之增大．而断裂韧性则先增后减,在ZrB2质量分数为21％时,其断裂韧性达最大值。利用金相显微镜和扫描电镜观察多晶试样的微观组织及断口形貌,初步分析了复合材料的增韧机制。     

Microstructure characterization and compressive performance of 3D needle-punched C/C–SiC composites fabricated by gaseous silicon infiltration

3D needle-punched C/C-SiC composites were fabricated from carbon fiber reinforced carbon (C/C) preforms, with densities of 1.05?g/cm³ and 1.28?g/cm³, by the gaseous silicon infiltration (GSI) method at fabrication temperatures from 1500?°C to 1800?°C. The compressive strengths and elastic moduli in transverse direction are larger than those measured under longitudinal compression except that samples fabricated from 1.28?g/cm³ density exhibit lower elastic moduli in transverse direction than in longitudinal direction. The compressive strength and modulus increase with fabrication temperature at 1500?°C and 1600?°C, and then decrease with higher fabrication temperature. Samples fabricated from the lower density C/C preforms have greater compressive strength and modulus. X-ray tomography was applied before and after the mechanical tests to characterize the microstructure and damage patterns, and the results indicated that for C/C-SiC composites fabricated at 1700?°C from 1.28?g/cm³ density C/C preform the matrix has a volume fraction (vol%) of 36.9%, and the initial intra-bundle cracks (0.6?vol%) display a space crossing structure while the inter-bundle pores (6.0?vol%) are special irregularly distributed.     

Axial compressive strength of carbon fiber

Efforts were made to estimate the axial compressive strengths of carbon fibers from the fiber fragment lengths produced by subjecting to a strain greater than the fiber ultimate strain for PAN-based and pitch-based carbon fibers. The estimated compressive strength of carbon fibers decreases with increasing temperature in a temperature range from room temperature to 100°C. This decrease in compressive strength may be accounted for by a decrease in the radial compressing force. The real compressive strength, determined by extrapolating a linear relationship between the estimated compressive strength and the radial compressing force, is approximately 25–60% of tensile strength for PAN-based fibers, while it is approximately 10–35% for pitch-based fibers.     

Compressive Fiber Fragmentation in Carbon/Polypropylene Composites: Effects of Residual Thermal Stresses and Transcrystallinity

The effects of fiber volume fraction and transcrystallinity in single fiber composites, on the phenomenon of compressive fiber fragmentation due to residual thermal stresses, are studied. A concentric cylinder model is used, jointly with experimental data, to predict the Weibull shape parameter of the compressive strength distribution of pitch-based high and medium modulus (HM and MM) carbon fibers, with isotactic polypropylene as the semi-crystalline embedding matrix. A severe effect of the fiber content on the thermal residual stress in the fiber and, thus, on the fiber break density, is predicted and experimentally confirmed. The effect of the presence of isothermally grown polypropylene transcrystalline interlayers (using pitch-based HM carbon fibers as a substrate) on the compressive stresses induced upon subsequent quenching is investigated, both experimentally and theoretically. Cooling rate results are also presented. The thermoelastic constants of the interlayer are predicted to have a severe effect on the residual stresses generated in the fiber, the interphase, and the matrix. There is therefore, a definite need for direct experimental measurements of these constants.     

MCMB–SiC composites; new class high-temperature structural materials for aerospace applications

Graphite–silicon carbide (G–SiC), carbon/carbon–silicon carbide (C/C–SiC) and mesocarbon microbeads–silicon carbide (MCMB–SiC) composites were produced using liquid silicon infiltration (LSI) method and their physical and mechanical properties, including density, porosity, flexural strength and ablation resistance were investigated. In comparison with G–SiC and C/C–SiC composites, MCMB–SiC composites have the highest bending strength (210 MPa) and ablation resistance (9.1%). Moreover, scanning electron microscopy (SEM) and optical microscopy (OM) are used to analyze the reacted microstructure, pore morphology and pore distribution of carbon-based matrices. As a result, SiC network reinforcement was formed in situ via a reaction between liquid silicon and carbon. The unreacted carbon and solidified silicon are two phases present in the final microstructure and are characterized by X-ray diffraction (XRD). Based on the results obtained and the low-cost processing of pitch-based materials, the MCMB–SiC composite is a promising candidate for aerospace applications.     

新型炭纤维/泡沫炭预制体的制备及致密化研究

由炭纤维/酚醛树脂经过发泡、固化和炭化制备出4种不同炭纤维含量(3%,7%,10%和15%)的泡沫炭作为制备炭/炭复合材料新型预制体,通过等温化学气相沉积对预制体进行致密化处理。研究了炭纤维含量对预制体微观结构、致密化过程及力学性能的影响。结果表明:炭纤维含量增加,使预制体产生更多的微裂纹,并有更多的炭纤维裸露在泡沫炭韧带外,有助于提高化学气相沉积的沉积速率。炭纤维/泡沫炭预制体炭/炭复合材料压缩强度随着预制体中炭纤维含量的增加而增加,当炭纤维体积分数为10%时,压缩强度达到峰值,为43MPa。