碳/碳复合材料中不同微区的基体结构

为优化碳基体结构,提高碳/碳(C/C)复合材料综合性能,针对沥青基C/C复合材料中纤维束内及纤维束间不同碳基体结构微区,利用显微Raman光谱、原位纳米力学测试、Micro-CT、扫描电镜(SEM)和压汞仪对碳基体结构进行研究。结果表明:碳基体呈片层结构沿纤维、纤维束表面取向堆积排列,在纤维、纤维束表面区域及纤维束之间碳基体中存在一定孔隙、裂纹等缺陷;纤维间基体的石墨化程度是沿着纤维表面向中心区域逐步增强,靠近纤维表面区域基体的弹性模量高于纤维间区域的弹性模量。C/C复合材料中碳基体形成过程存在渐次性和差异性,从而影响C/C复合材料综合力学性能。     

On the liquid-phase technology of carbon fiber/aluminum matrix composites

The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers' surface. This paper aims to solve these problems. The theoretical and experimental dependence of porosity on the applied pressure were determined. The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown. The correlation among the strength of the carbon fiber reinforced aluminum matrix composite, the fracture surface, and the degradation of the carbon fiber surface was discussed.     

碳纤维木质复合材料电镜图像分析及形态特征研究

图像分析同图像处理、计算机图形学等研究内容密切相关,而且相互交叉重叠.将改进的抗噪声能力强并考虑邻域像素的模糊C均值聚类算法应用到碳纤维木质复合材料研究中,经过试验验证取得了满意的分割结果.然后对分割结果进行碳纤维特征参数提取,并设置一个碳纤维分布形态参数r来区分电镜图像中碳纤维有无黏连成束.本研究为碳纤维木质复合材料均匀化识别提供了便捷的方法,同时也为后期构建碳纤维木质复合材宏微观模型提供数据支持.     

短切碳纤维C/SiC陶瓷基复合材料的动态力学性能研究

对三种不同短切碳纤维体积含量(16%、21%、24.8%)的C/SiC复合材料利用分离式霍普金森压杆(SHPB)装置进行了常温下的冲击力学试验。根据不同应变率下的试验结果分析了其动态破坏强度和应变率效应的关系,阐明了其破坏机理。实验结果表明:三种短切碳纤维体积含量的C/SiC陶瓷基复合材料的动态应力-应变曲线光滑无震荡,且具有一定的自相似性。在近似平均应变率下,当短切碳纤维体积含量的不断提高,则C/SiC复合材料的破坏程度不断降低,整体性越来越好,说明短切碳纤维体积含量的提高对C/SiC复合材料的强度有着积极的作用。     

Influence of applied load on wear behavior of C/C-Cu composites under electric current

Using carbon fiber needled fabrics with Cu-mesh and graphite powder as the preform, Cu mesh modified carbon/carbon(C/C-Cu) composites were prepared by chemical vapor deposition (CVD) with C3H6 and impregnation-carbonization (I/C) with furan resin. C/C composites, as a comparison, were also prepared. Their microstructures and wear morphologies were observed by optical microscopy (OM) and scanning electron microscope (SEM), respectively. Wear behavior of C/C and C/C-Cu composites under different applied loads were investigated on a pin-on-disc wear tester. The results show that Cu meshes are well dispersed and pyrolytic carbon is in rough laminar structure. Both C/C and C/C-Cu composites had good wear properties. The current-carrying capacity of C/C-Cu composites increases and the arc discharge is hindered as the applied load increases from 40 N to 80 N. Both C/C and C/C-Cu composites had good wear properties. The mass wear rate of C/C-Cu composites under 80 N was only 4.2% of that under 60 N. In addition, C/C-Cu composites represent different wear behaviors because wear mechanisms of arc erosion, abrasive wear, adhesive wear, and oxidative wear are changing under different applied loads.     

Fabrication of solid-phase-sintered SiC-based composites with short carbon fibers

Solid-phase-sintered SiC-based composites with short carbon fibers (Csf/SSiC) in concentrations ranging from 0 to 10wt% were prepared by pressureless sintering at 2100°C. The phase composition, microstructure, density, and flexural strength of the composites with different Csf contents were investigated. SEM micrographs showed that the Csf distributed in the SSiC matrix homogeneously with some gaps at the fiber/matrix interfaces. The densities of the composites decreased with increasing Csf content. However, the bending strength first increased and then decreased with increasing Csf content, reaching a maximum value of 390 MPa at a Csf content of 5wt%, which was 60 MPa higher than that of SSiC because of the pull-out strengthening mechanism. Notably, Csf was graphitized and damaged during the sintering process because of the high temperature and reaction with boron derived from the sintering additive B₄C; this graphitization degraded the fiber strengthening effect.     

原位法制取碳纳米管/尼龙6复合材料

为改善尼龙 6 (PA6 )的力学性能 ,加入碳 nm管(CNTs)与之复合 ,制作 CNTs/ PA6复合材料 ,以提高基体PA6的力学性能 ,特别是抗拉强度。通过采用原位法复合CNTs与 PA6 ,获得了由 OC C化学键连接的、理想的CNTs/ PA6界面的、且 CNTs在基体 PA6中分散均匀的CNTs/ PA6复合材料 ,其抗拉强度有较大幅度的提高 ,同时还保持较高的冲击韧性和延伸率。经检测 ,CNTs/ PA6复合材料的断裂界面不象其它纤维增强 PA6复合材料那样在纤维 / PA6界面上 ,而是在 PA6包裹层与 PA6基体界面上。研究结果表明 ,采用原位复合法 ,CNTs能够对 PA6基体起到很好的增强作用     

碳纤维水泥基复合材料导电机理的探讨

通过研究水泥基体的导电性能和不同纤维掺量、外力作用下及掺入骨料后的碳纤维水泥基复合材料的导电性能,探讨碳纤维水泥基复合材料的导电机理.研究表明,水泥基体的电阻随水化时间显著增加,其导电机理是强电解质溶液的离子导电;碳纤维水泥基复合材料的电阻率随纤维掺量增加而显著降低,其电导由接触导电、隧道导电和离子导电3种机制共同决定;碳纤维水泥基复合材料在压力作用下,电阻率因界面接触的改善和纤维搭接概率的增加而降低,在拉力作用下,电阻率因纤维的拔出、折断而提高;骨料的引入增加了复合材料的电阻,这是由于骨料增加了纤维分散的难度和折断的概率,同时阻碍了纤维的搭接并提高了隧道势垒.     

电化学处理程度对碳纤维结构及性能的影响

采用质量分数为5%NH4HCO3溶液对聚丙烯腈(PAN)基碳纤维进行不同程度的电化学处理。采用X射线光电子能谱(XPS)和拉曼光谱(Raman)表征电化学处理前后碳纤维表面化学成分和表面微观结构的变化规律。将碳纤维样品与环氧树脂制成复合材料,探究该复合材料的层间剪切强度(ILSS)。研究结果表明:经过3组电化学处理后,碳纤维表面含氧官能团增多、表面有序度下降、复合材料的ILSS提高1.94倍;继续经过3组电化学处理,碳纤维表面含氧官能团下降、表面有序度回升、复合材料的ILSS提高1.53倍;纤维表面含氧官能团含量越多,纤维的结构破坏程度越低,碳纤维/环氧树脂复合材料的ILSS越高。在大规模电化学处理碳纤维过程中,选择3组电化学处理碳纤维,既能大幅度改善碳纤维表面活性,又不会严重影响碳纤维的表面结构。     

编织结构三维仿真及其对C/SiC复合材料性能的影响

以连续碳纤维增强的碳化硅复合材料为研究对象,利用计算机仿真技术实现了纤维预制体结构的三维仿真;同时采用CVD PIP联合工艺制备了2.5D与三维四向2种结构的C/SiC复合材料,研究了预制体结构与复合材料力学性能之间的关系。结果表明:三维四向编织结构C/SiC复合材料的x向弯曲强度达到399.2 MPa,层间剪切强度达到38.1 MPa,断裂韧性达到16.0 MPa.m1/2,各项力学性能均高于2.5D编织结构的C/SiC复合材料的力学性能。     

毡体密度对C/C复合材料增密和结构的影响

用液化石油气作碳源、针刺炭毡作增强体,在自行设计的多元耦合物理场CVI炉中制备炭/炭(C/C)复合材料,在毡体内部设置石墨纸作发热体,并研究了一次性沉积15 h后,毡体密度对增密速度和材料结构的影响.采用偏光显微镜研究了沉积炭的显微结构,用XRD均峰位法研究了材料的石墨化度,并用排水法测量材料的表观密度.研究表明, CVI工艺增密速度随毡体密度的增加呈下降趋势,而较高的毡体密度有利于获得较高石墨化度的高织构的粗糙层结构(RL)热解炭.图4,参15.     

碳/碳复合材料表面烧蚀多尺度粗糙度模拟简

通过建立碳/碳（C/C）复合材料在宏观、微观不同尺度上的烧蚀模型,利用有限元方法分析了C/C复合材料在烧蚀过程中的体积损失、表面粗糙度以及烧蚀性能的变化规律。微观上,模拟了材料烧蚀呈现的尖笋状粗糙度形貌。宏观上,采用ALE方法,并基于实验结果通过Fortran编程控制材料表面烧蚀后退运动,建立了C/C复合材料表面烧蚀的多尺度热力耦合分析模型,并进行瞬态有限元分析。结果表明：材料烧蚀表面粗糙度程度与烧蚀速率、材料性能密切相关;并且随着材料烧蚀程度的不同,材料的表面应力也相应变化。     

碳纤维及其复合材料的发展及应用

叙述了碳纤维的结构形态、分类以及在力学、物理、化学方面的性能,介绍了碳纤维增强复合材料的特性,着重阐述了碳纤维增强树脂基复合材料中基体的分类、选择和应用,指出了碳纤维及其复合材料进一步发展的趋势。     

Microst ructure andflexural properties of carbon/ca rbon composite with in-situ grown carbon nanotube as secondary reinforcement

Carbon nanotubes (CNTs) were in-situ grown in carbon felts using ferric chloride as catalyst and natural gas as carbon precursor via thermal gradient chemical vapor infiltration (TGCVI). Subsequently, the carbon felts were densified to obtain CNT reinforced carbon/carbon (C/C) composites in the same furnace. Effects of CNTs on the microstructure and flexural property of C/C composites were investigated by polarized light microscopy, Raman spectroscopy, scanning electron microscopy and universal mechanical testing machine. The results of PLM observation and Raman analysis showed that CNTs have two-sided effects on the microstructure of pyrocarbon: the pyrocarbons in the region without CNTs show medium texture; while, in the region full of CNTs, the microstructure was low-textured or even isotropic though the TGCVD conditions would lead to the deposition of pure low texture pyrocarbons. Analysis based on stress-strain curves demonstrated that the flexural strength increased first and then decreased with the CNT content increasing. When the CNT content was 5.23 wt%, the flexural strength was maximum and had a nearly 35% improvement compared with pure C/C composite. Besides, after adding CNTs, the flexural modulus of the composites decreased and the ductility increased obviously, indicating CNTs can toughen C/C composites.     

原位生长碳纳米管增强SiCf/SiC复合材料的力学性能简

碳化硅纤维增强碳化硅复合材料（SiCf/SiC）是航空航天和聚变能源等高技术领域理想的高温结构材料,改善纤维与基体的界面结合是提高其力学性能的关键。本文采用化学气相沉积法在纤维表面原位生长碳纳米管,以达到改善纤维与基体的结合同时对复合材料进行二次增强的目的。结果表明,采用碳纳米管增强的SiCf/SiC复合材料的力学性能有不同程度的提高,特别是当碳纳米管的体积分数为5．31％时,复合材料的断裂韧性提高106．3％。纤维表面的碳纳米管层与纤维结合较弱,能够促进纤维的拔出,从而促进复合材料断裂韧性的提高;另外,碳纳米管的拔出对复合断裂韧性的提高也有一定的促进作用。     

循环伏安法对PAN基高模碳纤维阳极氧化表面处理的研究

以未表面处理的PAN基高模碳纤维(HMCF)为工作电极,分别用NH4H2PO4、NH4HCO3和KOH为电解质,进行循环伏安多重扫描,以研究HMCF在不同电解质中的电化学反应行为以及电解质的氧化能力。同时采用连续恒流阳极氧化的方法对HMCF进行表面处理,验证循环伏安法得到的结论。通过联碱滴定、SEM等方法表征处理前后纤维表面官能团、表面形貌的变化;处理前后纤维与环氧树脂界面粘接性能的变化通过层间剪切强度(ILSS)表征。循环伏安结果显示:在NH4H2PO4溶液中扫描时氧化反应峰值电流最高,表明纤维表面生成的官能团最多;在KOH溶液中扫描时平台电流最高,表明纤维表面粗糙度提高幅度最大。联碱滴定结果表明NH4H2PO4溶液处理后纤维表面官能团含量提高最多;SEM结果显示KOH溶液处理后纤维表面粗糙度增加最明显;这两点验证了循环伏安多重扫描的结果。用NH4H2PO4、KOH处理后的纤维与环氧树脂ILSS达到75MPa、60MPa,分别提高240%和170%。     

连续损伤力学在复合材料厚壁圆筒渐进破坏分析中的应用

为研究复合材料枪管破坏机理,基于连续损伤力学理论,该文采用以能量为基准的刚度退化方法预测了钢-碳纤维/聚酰亚胺复合材料厚壁圆筒的渐进破坏行为。模型考虑了碳纤维/聚酰亚胺复合材料的三种破坏模式:纤维断裂、基体损伤和层间剪切失效。在渐进破坏分析中,采用了包括多帧重启动分析和弧长法的三维有限元技术。计算结果表明:基体首先破坏;随后纤维开始断裂,引起整体结构屈服破坏;这个过程中没有层间剪切失效和内衬单元破坏;厚壁圆筒整体的强度主要受纤维强度的影响。     

碳纤维水泥基复合材料温敏特性研究

简单介绍了碳纤维水泥基复合材料的制备及其电阻率测试方法,研究了不同掺量的碳纤维水泥基复合材料电阻率随温度变化的规律.研究结果表明,碳纤维水泥基复合材料具有温敏特性,在温度升高的初始阶段,试件电阻率随温度的升高而下降,呈现NTC效应;当温度升高到一定数值,电阻率随温度的升高而逐渐升高,呈现出PTC效应,并且随着碳纤维掺量的变化,NTC/PTC转变温度也发生变化.基于试验结果,对NTC/PTC效应的转变机理进行了初步探讨.     

Microstructure and properties of SiC gradiently coated Cf/C composites prepared by a RCLD method

The SiC gradiently coated carbon fiber/carbon (C_f/C) composites were prepared by a two-step rapid chemical liquid deposition (RCLD) method. The microstructure and properties of the composites were investigated using X-ray diffraction, scanning electron microscopy together with energy dispersive X-ray analysis, bending tests, and oxidation tests. The experimental results show that the surface layer of the composites is composed of SiC, pyrocarbon, and carbon fibers. Their inner area consists of pyrocarbon and carbon fibers. The SiC content gradiently decreases with increasing distance from the outer surface to the center of the composites. Furthermore, the thickness of the SiC layer increases with increasing tetraethylorthosilicate content and deposition time. SiC coatings have no significant influence on the bending strength of the composites. However, the oxidation resistance of the composites increases with increasing thickness of the SiC layer.     

碳纤维/玻璃纤维混编编织复合材料顶盖中横梁三点弯强度分析

根据二维三轴编织复合材料中碳纤维束和玻璃纤维束的空间几何特征,建立了碳纤维/玻璃纤维混编复合材料刚度预报模型;基于Tsai-Wu准则建立了该二维三轴编织复合材料的强度预报模型,提出了针对编织复合材料结构渐进失效分析的一般流程;设计了相应的材料试验,验证了理论模型的有效性;最后,对使用了该材料的顶盖中横梁进行了三点弯强度分析。结果表明横梁容易发生破坏的位置集中在接触位置和棱角上。