电磁波与复合材料板上传输线的耦合分析

利用单层均匀模型等效非均匀碳纤维复合材料,获得等效电磁参数,进而采用基于全波分析方法的仿真软件研究了碳纤维的排列方向以及入射波参数对传输线终端负载感应电流的影响。结果表明,当导线与碳纤维方向平行时,其场线耦合规律与同电导率导电板上的场线耦合变化规律基本一致,且负载感应电流大于导线与碳纤维正交时的感应电流。当电磁波垂直于复合材料板入射时,负载感应电流大于同等条件下电磁波平行入射时的感应电流。     

碳纤维复合材料在航天领域的应用

综述了碳纤维复合材料的应用现状和发展前景。首先,概述了碳纤维的分类和力学性能以及碳纤维复合材料的特性;重点介绍了碳纤维复合材料在国内外航天领域,特别是在卫星结构、运载火箭、精密支撑构件以及空间镜体等方面的应用情况。指出了目前碳纤维复合材料的主要问题是湿热效应。最后,结合我国国情,对碳纤维复合材料需要解决的问题提出了一些建设性的措施。     

碳纤维复合材料在航天领域的应用

综述了碳纤维复合材料的应用现状和发展前景。首先,概述了碳纤维的分类和力学性能以及碳纤维复合材料的特性;重点介绍了碳纤维复合材料在国内外航天领域,特别是在卫星结构、运载火箭、精密支撑构件以及空间镜体等方面的应用情况。指出了目前碳纤维复合材料的主要问题是湿热效应。最后,结合我国国情,对碳纤维复合材料需要解决的问题提出了一些建设性的措施。     

具有碳纤维材料环的超高压模具

介绍了一种使用钢环和碳纤维复合材料环共同预紧方式的两面顶超高压模具,该结构在全钢环两面顶模具的基础上,使用一层碳纤维复合材料环代替最外层钢环,得到了一种具有碳纤维复合材料环的超高压模具。这种设计避免了大直径钢环难以制造加工的问题,形成一种以钢环与复合材料环共同对压缸预紧的新型预紧方式。数值分析表明:该模具结构设计具有可行性,可以在一定程度上减小压缸的周向应力、最大剪切应力和等效应力。此外,对碳纤维复合材料环进行了失效判别。     

树脂基复合材料在连续激光作用下的损伤

 采用热压工艺制备了碳纤维布和高硅氧纤维布增强的环氧树脂和酚醛树脂基复合材料,研究了不同功率密度连续激光辐照下,复合材料的破坏形式及其组织结构与力学性能的变化。结果表明：当激光辐照功率密度大于0.1 kW/cm²后,树脂基体产生燃烧,碳纤维没有明显的损伤,而玻璃纤维布开始熔融,复合材料的拉伸性能降低30%~40%;当功率密度达到1 kW/cm²以后,除基体燃烧外,碳纤维复合材料产生明显的鼓泡分层,表层碳纤维有少量破断,而高硅氧纤维产生明显的熔融烧损,复合材料的拉伸性能降低80%以上。采用有限元计算方法,对碳纤维增强环氧树脂复合材料在连续激光辐照下的温度场进行了研究,计算结果与实验中复合材料的损伤行为相吻合。     

国外碳纤维复合材料空间反射镜技术研究与应用进展

采用碳纤维复合材料(CFRP)制造反射镜是空间光学系统轻量化的发展趋势。详细地阐述了国外科研机构在碳纤维复合材料反射镜方面开展的全面基础研究,特别是美国复合材料反射镜研究应用公司(CMA)、伦敦大学学院UCL在这方面的研究情况。阐明了以PLANCK、RICH、NPOI和ULTRA等项目的高精度反射镜为典型代表的工程应用情况,介绍了碳纤维复合材料反射镜的最新研究情况,包括碳纳米管/环氧树脂制造反射镜和镜面非接触方法加工。     

基于原位测量的复合材料冲击损伤定位

针对连续碳纤维增强环氧树脂基复合材料层合板和玻璃纤维(GF)增强环氧树脂基复合材料层合板两类典型结构,开展了基于原位测量的冲击损伤定位研究。利用碳纤维/环氧树脂基复合材料层合板自身的导电性,设计了电极阵列,考察了板厚对定位结果的影响;对于不导电玻璃纤维/环氧树脂基复合材料层合板,设计并制备了多壁碳纳米管涂覆的玻璃纤维束(MWCNT@GF)传感器,并将MWCNT@GF嵌入层合板中形成传感网络,考察了不同入射角度对定位结果的影响。对于上述两种方法,编制了冲击损伤成像算法。结果表明:利用冲击前后碳纤维自身电阻和嵌入MWCNT@GF传感器的方法,可准确定位碳纤维/环氧树脂基复合材料层合板和玻璃纤维/环氧树脂基复合材料层合板的冲击损伤。     

镀镍碳纤维复合材料的电磁脉冲屏蔽效能

研究了连续碳纤维表面化学镀镍工艺,并利用扫描电子显微镜(SEM),X射线衍射仪(XRD)分析了纤维的微观形貌、镍层成分和镍层结构。测试了镀镍碳纤维和镀镍碳纤维复合材料的导电性能。制备了镀镍纤维为增强材料的抗电磁脉冲复合材料。在场强大于20kV/m的环境下测试了复合材料在频率为1.3,2.8,4.3,9.4GHz处的高功率微波电磁脉冲屏蔽效能。结果表明复合材料的高功率微波电磁脉冲屏蔽效能均大于60dB,其中2.8GHz下出现最大值91dB。     

屏蔽复合材料设备舱电磁脉冲屏蔽效能

利用镀镍碳纤维为基础材料,制作了镀镍碳纤维复合材料蒙皮,并辅以玻璃纤维复合材料蒙皮和聚氨酯泡沫以及其他配件制作了全复合材料轻质设备舱。研究了其在核电磁脉冲(HEMP)、间接雷击电磁脉冲(LEMP)下的防护性能。结果表明,基于镀镍碳纤维复合材料的轻质设备舱在上升时间2.8ns、半脉宽24ns脉冲波形下,HEMP屏蔽性能达到50.1dB;在上升时间3.2μs、半脉宽40.3μs脉冲波形下,LEMP屏蔽性能达到57.2dB。     

基于埋入式应变片的纤维缠绕压力容器的健康监测

在玻璃纤维缠绕金属内胆复合材料压力容器的制备过程中,将应变传感器埋在金属内胆与玻璃纤维/环氧树脂复合材料层之间,得到了具有原位监测功能的纤维缠绕压力容器。对该纤维缠绕压力容器开展水压疲劳和爆破实验。疲劳压力的最大值和最小值分别为25 MPa和2 MPa,最大疲劳周次为5700;打压爆破压力为零到爆破压力,打压速率为2 MPa/s。实验过程中,利用埋入式应变传感器原位监测了压力容器的应变变化,建立了不同载荷作用下纤维缠绕压力容器的应变与受载情况之间的关联。结果表明:采用埋入式应变传感器监测纤维缠绕压力容器的健康状况具有可行性;该方法在保护应变传感器不受外载荷破坏的前提下,原位监测了压力容器在疲劳和爆破实验中的应变变化趋势。     

Conduction noise absorption by fiber-reinforced epoxy composites with carbon nanotubes

Nearly all electronic equipment is susceptible to malfunction as a result of electromagnetic interference. In this study, glass fiber, and carbon fiber as a type reinforcement and epoxy as a matrix material were used to fabricate composite materials. In an attempt to increase the conduction noise absorption, carbon nanotubes were grown on the surface of glass fibers and carbon fibers. A microstrip line with characteristic impedance of 50 Ω in connection with network analyzer was used to measure the conduction noise absorption. In comparing a glass fiber/epoxy composite with a GF-CNT/Ep composite, it was demonstrated that the CNTs significantly influence the noise absorption property mainly due to increase in electric conductivity. In the carbon fiber composites, however, the effectiveness of CNTs on the degree of electric conductivity is negligible, resulting in a small change in reflection and transmission of an electromagnetic wave.     

The effect of interphase modification on carbon fiber/polyarylacetylene resin composites

Interfacial modification for carbon fiber (CF) reinforced polyarylacetylene (PAA) resin, a kind of non-polar, was investigated. The high carbon phenolic resin was used as coating to treat the surface of CF after oxidation. Atomic force microscopy (AFM) with force modulation mode was used to analyze the interphase of composite. The interlaminar shear strength (ILSS) and mechanical properties of CF/PAA composites were also measured. It was found that the CF/PAA composites treated with oxidation and coating after oxidation had transition area between carbon fiber and PAA resin. The existence of transition area led to the improvement of interfacial performance of composites. Specially, the thickness and stiffness of interphase of composite treated with coating after oxidation were more suitable for CF/PAA composites. Thus, the composite treated with coating after oxidation had the highest value of ILSS and the best mechanical properties.     

The effect of surface treatment of carbon fiber on the flexural property of thermoplastic polyimide composite

Rare earth solution (RES) surface modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber reinforced polyimide (CF/PI) composite. The flexural property of the PI composites reinforced by the carbon fibers treated with different surface modification methods was comparatively investigated. Results showed that the flexural strength of CF/PI composite was improved after RES treatment. The improvement of impact and flexural property of the CF/PI composite was mainly due to the improvement in interfacial adhesion after RES treatment. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that the oxygen concentration was obviously increased after RES treatment. The increase in the amount of organic functional groups increased the interfacial adhesion between CF and PI matrix.     

Interfacial interaction in carbon fiber/thermoplastic composites

This work was undertaken in order to increase the understanding of the mechanism responsible for fiber/matrix interaction in carbon fiber/thermoplastic composite. From results of previous study on carbon fiber/PEEK composite, which suggested that the formation of the fiber/ matrix interaction was primarily related to a chemisorption mechanism, a study was done of the conditions required to obtain efficient fiber/matrix interaction in PA-12 and PP/carbon fiber composites. The interest in studying carbon fiber composite based on PP and PA-12 was that these two matrices are very different in terms of reactivity, polyamide having many more reactive groups than polypropylene. As expected, due to the non-reactive chemical structure of the polypropylene, fiber/matrix interaction in carbon fiber/PP composite occurred only when the matrix was thermally degraded, i.e. when the composite was molded at high temperature or under long residence time at the melt temperature. For the carbon fiber/PA-12 composite, strong fiber/matrix interaction occurred readily at relatively low molding temperature, i.e. well before thermal degradation of the matrix. It was also found that the short beam shear strength in these composites seems to evolve with molding temperature, and a maximum interfacial strength was observed at a molding temperature corresponding to the thermal degradation of the matrix. This indicates that although matrix degradation often results in strong reduction in the composite performance, some matrix degradation can be beneficial in terms of interfacial mechanical properties. Finally, this work demonstrated that while the formation of fiber/matrix interaction seems to be primarily related to a chemisorption mechanism, the contribution of interphase crystallinity to the interfacial strength is not negligible. In fact, interfacial crystallinity was found to be essential to ensure optimum interfacial strength.     

Geometrically nonlinear free vibration of shear deformable piezoelectric carbon nanotube/fiber/polymer multiscale laminated composite plates

The nonlinear free vibration of carbon nanotubes/fiber/polymer composite (CNTFPC) multi-scale plates with surface-bonded piezoelectric actuators is studied in this paper. The governing equations of the piezoelectric nanotubes/fiber/polymer multiscale laminated composite plates are derived based on first-order shear deformation plate theory (FSDT) and von Kármán geometrical nonlinearity. Halpin–Tsai equations and fiber micromechanics are used in hierarchy to predict the bulk material properties of the multiscale composite. The carbon nanotubes are assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. A perturbation scheme of multiple time scales is employed to determine the nonlinear vibration response and the nonlinear natural frequencies of the plates with immovable simply supported boundary conditions. The effects of the applied constant voltage, plate geometry, volume fraction of fibers and weight percentage of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on the linear and nonlinear natural frequencies of the piezoelectric nanotubes/fiber/polymer multiscale composite plate are investigated through a detailed parametric study.     

切向气流和激光作用下碳纤维/环氧材料的损伤特性

无气流和切向气流马赫数分别为0.50,0.85条件下,开展了碳纤维/环氧材料激光辐照损伤特性研究实验,对碳纤维、环氧树脂和复合材料热失重曲线、温度历史曲线以及实验后复合材料损伤形进行分析,结果表明:由于切向气流阻止材料燃烧且对材料表面起冷却作用,无气流条件下材料的热损伤区域远大于激光辐照区域,与切向气流条件相比,材料后表面温升时间长、温升幅值高;在切向气流环境下,由于气流作用使得材料的损伤包括烧蚀损伤和断裂损伤;从损伤形貌和后表面温度历史、温升速率比较来看,在切向气流马赫数为0.50~0.85的速度范围内,碳纤维/环氧材料在切向气流和连续激光(102 W/cm2量级)联合作用下的损伤差异不明显。     

Fiber optic acoustic emission sensor and its applications in the structural health monitoring of CFRP materials

A fiber optic acoustic emission sensor based on fused-tapered coupler and its applications in structural health monitoring are proposed in this paper. The fiber optic acoustic emission sensor (FOAES) was tested using pencil lead break tests compared with the commercial acoustic emission sensor (R15 PZT). Besides, the sensor was embedded into the carbon fiber reinforced plastics (CFRP) materials and tested in the same way. It successfully detected the AE signals. FOAES was applied in the structural health monitoring (SHM) of CFRP materials. Damages of carbon fiber/epoxy composite laminates during three-point-bending test were monitored by surface-mounted and embedded FOAES, respectively. Results identified that the sensor embedded into composite structures could monitor damage of composite laminates on-line as the surface-mounted sensor did.     

The research on the interfacial compatibility of polypropylene composite filled with surface treated carbon fiber

Dielectric barrier discharges (DBD) in ambient air are used on carbon fiber to improve the fiber surface activity. Carbon fibers with length of 75 μm are placed into the plasma configuration. The interaction between modified carbon fibers and polypropylene (PP) was studied by three-point bending (TPB) test. The chemical changes induced by the treatments on carbon fiber surface are examined using X-ray photoelectron spectroscopy (XPS). XPS results reveal that the carbon fiber modified with the DBD at atmospheric pressure show a significant increase in oxygen and nitrogen concentration. These results demonstrate that the surface of the carbon fiber is more active and hydrophilic after plasma treatments using a DBD operating in ambient air.     

Enhanced interfacial adhesion between PMMA and carbon fiber by graphene oxide coating

The purpose of this study is to increase the interfacial properties in PMMA/carbon fiber (PMMA/CF) composites Graphene oxide (GO) and brached polyethyleneimine were coated onto the surface of carbon fiber by layer-by-layer assembly in this work. Compared with the origin PMMA/CF composite, the composites reinforced by PMMA/CF–GO showed significant enhancement in interFacial shear strength (IFSS). The improved fiber–matrix adhesion was proved by fracture morphology observation of scanning electron microscopy and almost unaffected mechanical properties of the fiber itself during the coating process. The optimal assembly time was found to be 10 for enhancing the overall composite mechanical performance.