纤维类型对C/SiC复合材料性能的影响

利用化学气相浸渗法制备了Cf-C/SiC复合材料,借助SEM、TEM等研究了纤维类型对Cf-C/SiC复合材料力学性能的影响.实验证明T300碳纤维增韧补强效果优于M40碳纤维,利用T300碳纤维制备出弯曲强度为459M,断裂韧性为20.0MPa*m1/2,断裂功为25170J/m2的Cf-C/SiC复合材料.2种碳纤维增韧效果的差异是由纤维的原始强度、热膨胀系数和弹性常数的不同决定的.     

Mechanical and Dielectric Properties of SiCf/AlPO4 Composites with Multi‐Walled Carbon Nanotubes

SiC_f/AlPO₄ composites were prepared by laminating method. The slurry comprising Al(H₂PO₄)₃ solution, multi‐walled carbon nanotubes (MWCNTs), and Al₂O₃ powder was used as matrix precursor. The complex permittivities of the composites were measured in the X‐band (8.2–12.4 GHz). The reflection loss was calculated using the transmission line theory. It was found that the addition of 2.5 wt% MWCNTs noticeably improved the absorption property of 3 mm thick composites with the assistance of 15 wt% Al₂O₃, which also exhibited an obvious toughened fracture behavior with 190 MPa fracture strength.     

纤维类型对Cf/SiC复合材料力学性能的影响

本工作以AIN和Y2O3为烧结助剂,采用先驱体转化－热压烧结的方法制备出了Cf/SiC复合材料,研究了纤维类型影响复合材料力学性能的本质原因,由于T300纤维的制备温度明显低于M40JB纤维的制备温度,因此,与M40JB纤维相比,T300纤维的石墨化程度较低且含有较多的杂质,从而导致T300纤维表面的活性强,而M40JB纤维表面的活性较弱,正是这种结构和成分的差别,使T300纤维与基体的结合较强,而M40JB纤维与基体的结合较弱,因此以T300纤维为增强的复合材料呈现脆性断裂,而以M40JB纤维为增强相的复合材料则呈现韧性断裂,谈复合材料具有较好的力学性能。     

PET/碳纳米管复合材料的结晶性能和力学性能研究

采用熔融共混法制备了聚对苯二甲酸乙二醇酯/碳纳米管(PET/CNT)复合材料。研究了CNT用量对PET/CNT复合材料结晶性能和力学性能的影响。结果表明:CNT对PET基体具有明显的异相成核作用,显著提高了PET的熔融温度和相对结晶度;PET/CNT复合材料的断裂强度和屈服强度随着CNT用量的增加先提高后降低,在CNT用量为1%时达到最大值;PET/CNT复合材料的断裂伸长率随着CNT用量的增加呈先降低后提高的趋势;随着CNT用量的增加,PET/CNT复合材料的弯曲强度和弯曲模量呈先增大后减小的趋势;而复合材料的冲击强度随着CNT用量的增加先减小后增大。     

聚双环戊二烯/碳纤维复合材料的制备和力学性质

采用扫描电镜(SEM)对分别经刻蚀、氧化及氧化后再刻蚀的碳纤维表面进行表征;用不同方法处理的碳纤维通过反应注射成型(RIM)技术制备出了聚双环戊二烯(PDCPD)/碳纤维复合材料,对材料的断面形貌和力学性能进行了表征.结果表明,在实验范围内,经过氧化后再刻蚀的碳纤维其复合材料力学性能提高较大,随着碳纤维含量的增加,复合...     

碳纤维/聚合物自润滑复合材料的机械及摩擦性能

采用以钢铁为基体高分子自润滑复合材料为衬层制作的传动件,兼有优良的减磨耐磨性能和高的承载能力。研究了组分对复合材料性能的影响,制备了机械和摩擦学性能好的碳纤维增强复合材料,其黏结强度和压缩强度分别达到16~18 MPa和85~91 MPa,冲击强度达19.67~23.45 kJ/m2;与锡青铜ZQSn6-6-3摩擦对比试验表明,复合材料在重载工况下具有更优良的摩擦性能,工作状况稳定,油摩擦因数为0.077,仅为ZQSn6-6-3的59%。试验还发现,轻载启动和在摩擦面开设润滑油槽有助于改善摩擦状况。     

聚合物/CNTs复合材料制备及其力学性能影响因素

综述了近年CNTs增强聚合物复合材料的制备方法,重点分析了制备过程中影响复合材料力学性能的主要因素,总结了聚合物/CNTs复合材料制备过程中存在的技术难题并对其未来的发展应用进行了展望。     

聚丙烯/碳纳米管微孔注塑发泡行为及力学性能

研究了不同含量单壁碳纳米管(CNT)的加入对聚丙烯(PP)流变、热稳定性及微孔注塑发泡行为和力学性能的影响。结果表明,随着CNT含量从不足1.0 %(质量分数,下同)逐渐增加,PP熔体黏度显著增大,热稳定性逐渐提升,即使CNT的加入量仅为0.15 %也会产生团聚现象,但团聚体尺寸较小且与基体结合紧密;微孔发泡注塑样品中泡孔分布不均匀,泡孔尺寸范围在10~70 μm,直径随着CNT含量增加呈现先减小后增大;PP/CNT复合材料微孔发泡成型后,弹性模量、屈服应力下降不大,但断裂伸长率平均提升了近400 %,不同组分发泡样品间力学性能指标变化不大。     

聚氨酯/碳纳米管功能复合材料的电学性能研究

采用溶液共混法制备了聚氨酯(PUR)/碳纳米管(CNTs)功能复合材料,并分别利用磁力分散和超声分散方法对CNTs进行分散,探讨了CNTs含量对PUR/CNTs复合材料电学性能的影响。结果表明,利用超声分散方法比磁力分散方法获得的CNTs在基体中的分散效果更好,并且随着超声分散时间的延长,分散效果越好;当分散时间为2 h、CNTs的质量分数为5%时,PUR/CNTs复合材料的体积电阻率趋于稳定,可以降到50 MΩ.cm,比纯PUR的体积电阻率下降了6个数量级。     

Model of Oxidation‐Induced Fiber Fracture in SiC/SiC Composites

Stress rupture of SiC/SiC composites at intermediate temperatures in oxidizing environments is the result of a series of internal chemical and thermomechanical processes that lead to premature, localized fiber fracture. This article presents analytical models for two potentially critical steps in this process. The first involves the generation of tensile stresses in the fibers due to SiO₂ scale formation (following removal of fiber coatings) and the associated reduction in the applied stress required for fiber fracture. The second occurs once the gaps produced by coating removal are filled with oxide and subsequent oxidation occurs subject to the constraints imposed by the matrix crack faces. In this domain, the failure model is couched in terms of the stress intensification within the fibers caused by constrained oxidation. The models incorporate the combined kinetic effects of oxide growth and viscous flow. The competing effects of increased oxidation rate and accelerated stress relaxation with increasing temperature on fiber stress feature prominently in the results. The results suggest that, in dry air environments, the highest risk of fiber fracture occurs at temperatures in the range 840°C–940°C. In this range, the oxide scales grow at appreciable rates yet the resulting growth stresses cannot be mitigated sufficiently rapidly by viscous flow.     

Interfacial Mechanical Characterization of Nicalon SiC Fiber/Alumina-Based Composites

Interfacial mechanical properties of both Nicalon SiC/aluminum borate and Nicalon SiC/aluminum phosphate with various fiber coatings and heat treatments were evaluated using a commercially-available indenter to induce fiber sliding during load cycling experiments. Varying degrees of sliding due to different coating materials were found. The interfacial characteristics including the shear, the residual axial fiber, and debond stresses were estimated by matching the experimental stress-displacement curves with curves predicted from an existing model. The elastic modulus and hardness of the interphase/interface in ceramic matrix composites were also evaluated. These results provided important insights into the ultimate mechanical performance of fiber-reinforced ceramic-matrix composites.     

Interfacial Mechanical Characterization of Nicalon SiC Fiber/Alumina-Based Composites

Interfacial mechanical properties of both Nicalon SiC/aluminum borate and Nicalon SiC/aluminum phosphate with various fiber coatings and heat treatments were evaluated using a commercially-available indenter to induce fiber sliding during load cycling experiments. Varying degrees of sliding due to different coating materials were found. The interfacial characteristics including the shear, the residual axial fiber, and debond stresses were estimated by matching the experimental stress-displacement curves with curves predicted from an existing model. The elastic modulus and hardness of the interphase/interface in ceramic matrix composites were also evaluated. These results provided important insights into the ultimate mechanical performance of fiber-reinforced ceramic-matrix composites.     

PP/碳纤维复合材料力学性能的研究

综合考虑碳纤维材料的加工适应性以及对基体力学性能改善的能力,分别选取了短切碳纤维和碳纤维粉末作为增强相,比较了它们对于PP的增强效果以及加工的难易,通过测定拉伸性能和冲击韧性考察了短切碳纤维的含量以及碳纤维粉末的含量对各自复合材料力学性能的影响。结果表明,随着碳纤维含量的增加,两种复合材料的冲击韧性以及拉伸性能都呈先增加后减小的趋势,短切碳纤维作为增强相对于基体树脂的力学性能增强效果更为显著,碳纤维粉末作为增强相的复合材料加工适应性强,性能更加稳定,该研究对碳纤维制品的实际注塑生产具有十分重要的意义。     

T700碳纤维／环氧复合材料力学性能试验研究

本文对日本东丽、东邦公司生产的T700碳纤维的单向板力学性能进行了试验研究,提供了两种纤维复合材料的标准试验数据;对于两种碳纤维的单向板纵向拉伸性能的差异,运用材料力学方法、最弱环定理进行了分析,发现TOHO T700碳纤维／环氧单向板拉伸强度较差的原因可能来自于纤维本身和隐含缺陷较多造成;同TOHO T700碳纤维相比较,TORAY T700碳纤维较为适用于纵向拉伸要求较高的产品。通过标准试验方法对TORAY与TOHO两种T700碳纤维进行单向板压缩性能、单向板层间界面性能比较表明,两者抗压性能,界面性能相近。     

Utilizing Vacuum Bagging Process to Prepare Carbon Fiber/CNT-Modified-epoxy Composites with Improved Mechanical Properties

In this work, the effects of carbon nanotube-modified epoxy and carbon nanotube-enriched sizing agent on the tensile properties and failure mode of unidirectional carbon fiber/epoxy composites were investigated. Laminates of carbon fiber/epoxy composites at different concentrations of carbon nanotube and sizing agent were fabricated by hand layup vacuum bagging process. Scanning electron microscopy analysis was conducted to unveil the relation between the macroproperties and the composites’ microstructure. Experimental results showed that the carbon nanotube-modified epoxy/carbon fiber composite showed 20% enhancements in the Young’s modulus compared to the pristine epoxy/carbon fiber composite. The scanning electron microscopy analysis of the fracture surfaces revealed that incorporating carbon nanotube into the epoxy matrix with utilizing the vacuum improves the interfacial bonding and minimizes the voids that act as crack initiators. This microstructure enhances the interfacial shear strength and load transfer between the matrix and the fabrics and consequently the tensile characteristics of the formulated composite.     

Comparative Analysis of Low‐Cycle Fatigue Behavior of 2D‐Cf‐PyC/SiC Composites in Different Environments

A carbon fiber‐reinforced silicon carbide matrix composite with pyrolytic carbon interface (C_f‐PyC/SiC) and a protective coating was prepared by isothermal low pressure chemical vapor infiltration. Low‐cycle fatigue behavior of this material system was investigated at high temperatures up to 1800°C in a combustion environment and at room temperature in air, respectively. The combustion environment includes thermal mechanical loading, high temperatures, and oxidizing atmosphere. Low‐cycle fatigue tests were conducted at a maximum stress level of 180 MPa but at various temperatures and fatigue cycles. The residual strength variation of fatigue‐survived samples was due to different damage mechanisms in different environments.     

多壁碳纳米管在国产碳纤维增强环氧树脂复合材料中应用

研究了一种简易有效的多壁碳纳米管(MWNTs)分散入环氧树脂的方法,对树脂的工艺性进行试验研究;使用碳纤维复丝的力学性能来表征纤维/树脂界面性能和纤维强度转化效果,制备了含MWNTs的环氧树脂/碳纤维预浸料,并对使用此预浸料制备的复合材料单向板进行力学性能测试。结果表明,当MWNTs的用量为E–51的0.5%时,二者混合球磨8 h后配制的树脂溶液适用期大于24 h,黏度小于0.8 Pa·s,树脂浇铸体拉伸强度78 MPa,弯曲强度106 MPa,断裂伸长率4.3%;添加MWNTs之后纤维/树脂结合良好,复合材料单向板拉伸强度提升了7.2%,弯曲强度提升了9.73%,压缩强度提升了6.82%,层剪强度提升了11.54%。     

羟丙基甲基纤维素对碳纤维增强环氧树脂力学性能的影响

为了提高短切碳纤维(CF)的分散性从而提高复合材料的力学性能,通过采用羟丙基甲基纤维素(HPMC)为分散剂的方法,研究了CF增强环氧树脂复合材料(EP/CF)的力学性能。利用扫描电子显微镜(SEM)研究了HPMC作为分散剂对CF在环氧树脂中分散的影响;并利用傅里叶红外光谱法(FTIR)和差示扫描量热法(DSC)分析了HPMC与基体的相互作用;采用动态热机械分析(DMA)和万能试验机表征复合材料的力学性能,通过SEM考察了材料断裂面的显微结构和断裂形态。研究表明:HPMC能有效分散CF,使得CF与环氧树脂E-51基体之间形成良好界面作用,复合材料的拉伸强度和冲击强度分别提高47.5%和62.7%。