取向碳纳米管/玻璃纤维增强树脂基单向层合板的制备及其力学性能

针对纤维增强树脂基单向复合材料横向刚强度低的问题,通过碳纳米管(CNTs)在单向复合材料横向方位取向控制技术研究,建立了一种CNTs在树脂基复合材料中电场取向装置,制备了取向CNTs/环氧树脂(EP)复合材料及取向CNTs/玻璃纤维(GF)增强环氧树脂基单向层合板,并对不同电场强度、CNTs含量对其力学性能的影响进行了试验分析。结果表明,施加300V/cm的取向电场时,添加0.2wt%多壁碳纳米管(MWNTs)/EP储能模量较未添加MWNTs时提高了68.42%,较随机方位分布MWNTs/EP提高了1.36%;取向MWNTs/GF增强单向层合板横向弯曲强度及模量比未添加MWNTs时分别提高了72.2%和92.1%,比随机方位分布MWNTs增强时分别提高了58.29%和61.43%;施加439V/cm的取向电场时,添加0.2wt%取向MWNTs/GF增强单向层合板横向弯曲强度及模量比未添加MWNTs时分别提高了64.7%和63%,比随机方位分布MWNTs增强时分别提高了51.42%和36.90%,取向CNTs/GF增强树脂基单向层合板横向刚强度均得到了大幅提高。     

含碳纳米管的新型抗静电纤维的制备和性能

将多壁碳纳米管分散在自制的抗静电载体PR-86中制备出新型、高效和耐久的抗静电母粒．抗静电母粒的添加量仅为0．5％就可以制备出性能优良的“基体-微纤”型抗静电PP纤维．该纤维的抗静电机理为异极性大分子放电机理．多壁碳纳米管的存在增强了微纤相的极化程度和抗静电母粒的抗静电效果．抗静电纤维的抗静电性具有耐久性．抗静电母粒对纤维的性能基本上没有影响．     

碳纳米管/聚砜纳米纤维增强增韧环氧树脂的研究

利用静电纺丝技术制备了碳纳米管/聚砜复合纳米纤维.由于碳纳米管的增强作用、聚砜的增韧作用以及聚砜纳米纤维良好的相容性,使得该复合纳米纤维对环氧树脂基体能够同时起到增强和增韧效果.应用透射和扫描电子显微镜表征了碳纳米管/聚砜复合纳米纤维的直径分布,通过测试拉伸和冲击性能分析了复合纳米纤维对环氧树脂的增强和增韧作用,对断裂表面微观形貌进行了观察,并测试了添加复合纳米纤维的环氧树脂动态力学性能.与环氧树脂基体相比,含3wt%CNTs的复合纳米纤维增强增韧环氧树脂的拉伸强度和模量分别提高13.9%和14.2%,冲击强度提高18.3%.     

取向碳纳米管/环氧树脂复合薄膜制备及结构与性能表征

碳纳米管(Carbon nanotube, CNT)/环氧树脂(Epoxy resin, EP)纳米复合材料中树脂含量、分布、CNT取向及其与树脂间界面结合是制备高性能纳米复合材料的关键因素。为了探究树脂分布和CNT/EP复合材料性能之间的关系,采用浮动催化化学气相沉积法制备的CNT薄膜和EP为原料,通过浸渍、牵伸、清洗和热压固化工艺制备CNT/EP复合薄膜。利用聚焦离子束结合扫描电子显微镜定性表征树脂在复合膜中的分布状态。结果表明,随着树脂含量增加,树脂在复合薄膜表面富集程度增加。在最优工艺条件下制备的纳米复合材料中CNT含量为66.14wt%, 拉伸强度和拉伸模量达到1405 MPa和46.7 GPa。      

碳纳米管含量对碳纳米管增强铝合金复合材料力学性能的影响

利用粉末冶金法制备碳纳米管增强铝合金复合材料,研究不同碳纳米管含量对材料力学性能的影响。采用扫描电子显微镜观察球磨粉末的微观形貌,并对碳纳米管的增强机制进行探讨。结果表明:随着碳纳米管质量分数的增加,复合材料的抗拉强度呈现先增大后减小的趋势。当CNT含量小于3%(质量分数)时,复合材料的强度与理论值基本一致;但CNT含量为5%(质量分数)时,复合材料的力学性能远低于理论值,这是由于当碳纳米管含量过高时,在铝合金基体中存在大量团聚,从而影响了复合材料力学性能的提高。     

碳纤维/碳纳米管增强基体多尺度混杂复合材料的研究现状和趋势

碳纳米管(Carbon Nanotube,CNT)具有非常优异的刚度和强度。CNT增强基体的传统连续纤维多尺度混杂复合材料既具有优良的纤维主导力学性能又有好的基体主导力学性能,具有广泛的应用前景。综述了国内外在碳纳米管增强基体的多尺度混杂复合材料力学性能,制备和数值模拟等方面的最新研究进展。提出了进一步研究需要解决的两个关键问题:(1)量化CNT对传统复合材料的增强效果;(2)阐明CNT对多尺度混杂复合材料的增强机制,并提出了相应的研究手段。     

取向碳纳米管膜/氰基树脂复合材料的制备与性能强化机制

以浮动催化化学气相沉积法(FCCVD)碳纳米管(CNT)膜为原料,通过氰基树脂溶液浸渍法制备CNT预浸膜,然后采用热辅助牵伸和热压固化的方法制备高取向CNT膜复合材料。详细分析了热处理的温度和树脂溶液浓度对CNT预浸膜拉伸性能的影响,从而得到合适的热辅助牵伸工艺,并考察固化工艺对复合材料性能的影响。在此基础上,从浸润特性、CNT取向程度和层间剪切性能方面揭示CNT膜复合材料力学性能的强化机制。结果表明与传统CNT膜牵伸工艺相比,CNT预浸膜热牵伸工艺更有利于制备高取向CNT膜复合材料。热牵伸的温度和树脂溶液的浓度是制备高取向、低孔隙CNT预浸膜的关键因素。通过固化工艺的改变可有效调控氰基树脂的反应程度碳纳米管薄膜/氰基树脂复合材料的拉伸性能。经高温后固化处理后,CNT膜/氰基树脂复合材料的拉伸强度和模量分别高达2 748 MPa和302GPa。优异的树脂浸润特性、层间剪切强度以及高的CNT取向度使CNT膜复合材料中CNT更有利于协同承载,从而提高其力学性能。     

碳纳米管含量对碳纳米管增强铝合金复合材料力学性能的影响

利用粉末冶金法制备碳纳米管增强铝合金复合材料,研究不同碳纳米管含量对材料力学性能的影响。采用扫描电子显微镜观察球磨粉末的微观形貌,并对碳纳米管的增强机制进行探讨。结果表明：随着碳纳米管质量分数的增加,复合材料的抗拉强度呈现先增大后减小的趋势。当CNT含量小于3G（质量分数）时,复合材料的强度与理论值基本一致;但CNT含...     

碳纳米管纤维力-电耦合效应的实验研究

CNT纤维是由沿轴向排列的高度取向的数十万根碳纳米管加捻组装而成。以实验方法研究CNT纤维在拉伸载荷与电流共同作用下的力学性质。实验结果表明,电流的引入会使纤维的模量和断裂强度显著降低。纤维在有电流通过时会产生轴向电致收缩力,电流强度越大,电致收缩力越大,在5mA时的收缩力约为2.5mN。将纤维轴向拉伸到2%应变,经过应力松弛使载荷趋于平稳后,首次通入电流或加大电流的强度,发现纤维的张力明显下降,主要原因是纤维模量变化引起的应力下降大于电致收缩力。在一定强度的电流下将纤维轴向拉伸到2%应变,经过应力松弛使载荷趋于平稳,然后改为通入相同强度的交流电流时,发现电致收缩力的响应很敏捷,当交流电流变化400个周期后,电致收缩力依然展现出较好的变化规律,这可使得CNT纤维作为新型电致驱动材料。     

石墨烯/聚酰胺6纤维的混合熔融纺丝工艺及性能EI北大核心CSCD

采用溶液混合冷冻干燥法制备了质量分数0.004%的石墨烯/聚酰胺6(PA6)粒料,再用2种工艺制备石墨烯/PA6纤维——石墨烯/PA6粒料直接熔融纺丝;石墨烯/PA6粒料加入双螺杆挤出机熔融混合、挤出、造粒、熔融纺丝。用万能试验机测试了纤维的拉伸性能;用差示扫描量热分析测试了纤维的熔融行为并计算了结晶度;用扫描电镜(SEM)观察了石墨烯/PA6纤维的微观形态。研究结果表明,微量石墨烯的加入能够显著改善PA6纤维的拉伸性能,制备的石墨烯/PA6纤维的拉伸强度和拉伸模量分别可达到270 MPa和9.4GPa;工艺一制备的石墨烯/PA6纤维的热力学性能优于工艺二;较高的熔融纺丝温度可提高纤维的拉伸强度、拉伸模量、熔点和结晶度;SEM分析表明,石墨烯较均匀地分散在PA6基体中,纤维表面均匀,无明显瑕疵。     

Effect of fiber diameter on the deformation behavior of self-assembled carbon nanotube reinforced electrospun Polyamide 6,6 fibers

High precision electrospinning technique was used to obtain self-assembled carbon nano-tube (CNT) reinforced polyamide (PA) 6,6 fibers. The reinforcement factors were critically evaluated with respect to the effects of fiber diameter and inclusion of CNTs. The average fiber diameter ranged from 240 to 1400 nm and the CNT contents were 0, 1 and 2.5 wt%. A sharp increase in modulus and strength of the fibers was demonstrated when the size of the fiber was decreased below ∼500 nm, which could be attributed to ordered arrangement of crystals and the spatial confinement effect of the fibers. Also, investigation of the deformation behavior of fibers as a function of CNT content revealed that tensile fiber modulus and strength improved significantly with increase of CNTs. Addition of CNTs restricted the segmental motion of polymer chains and provided the confinement effect to the neighboring molecules.     

Optimum dispersion conditions and interfacial modification of carbon fiber and CNT–phenolic composites by atmospheric pressure plasma treatment

Electric resistance measurements were used to determine the optimal dispersion conditions for carbon nanotubes (CNTs) in phenolic resins. Plasma treatment is frequently used to modify carbon fiber surfaces to improve adhesion of the fibers to matrices. Such treatment might also influence carbon fiber tensile strength. In order to determine the effect of atmospheric pressure plasma treatment on carbon fiber tensile strength and interfacial bonding strength, change in tensile strength of the fiber was studied at different gage lengths before and after the plasma treatment. The wettability of carbon fibers was improved significantly after only 10 s of plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from 65° to 28°. Surface energies of carbon fiber and CNT–phenolic composites were measured using the Wilhelmy plate technique, indicating that the work of adhesion between plasma treated carbon fibers and CNT–phenolic composites was higher than it before plasma modification. The interfacial shear strength (IFSS) and apparent modulus were also increased by plasma treatment of the carbon fibers.     

The effect of surface modification with carbon nanotubes upon the tensile strength and Weibull modulus of carbon fibers

Carbon fibers are widely used as reinforcements in composite materials because of their high specific strength and modulus. Today, a number of ultrahigh strength polyacrylonitrile (PAN)-based (more than 6?GPa), and ultrahigh modulus pitch-based (more than 900?GPa) carbon fibers have been commercially available. In contrast, carbon nanotube (CNT) with the extremely high tensile strength have attracted attention as reinforcements. An interesting technique to modify the carbon fiber is CNT grafting on the carbon fiber surface. CNT-grafted carbon fibers offer the opportunity to add the potential benefits of nanoscale reinforcement to well-established fibrous composites to create micro-nano multiscale hybrid composites. In the present study, the tensile properties of CNT grown on T1000GB PAN- and K13D pitch-based carbon fibers have been investigated. Single filament tensile test at gauge lengths of 1, 5, and 25?mm were conducted. The effect of gauge length on tensile strength and Weibull modulus of CNT-grafted PAN- and pitch-based carbon fibers were evaluated. It was found that grafting of CNT improves the tensile strength and Weibull modulus of PAN- and pitch-based carbon fibers with longer gauge length (≥5?mm). The results also clearly show that for CNT-grafted and as-received PAN- and pitch-based carbon fibers, there is a linear relation between the Weibull modulus and the average tensile strength on log–log scale.     

Comparison of chemical vapor deposition and chemical grafting for improving the mechanical properties of carbon fiber/epoxy composites with multi-wall carbon nanotubes

By engineering the fiber/matrix interface, the properties of the composite can be changed significantly. In this work, we increased the effective surface area of the fiber/matrix interface, to facilitate additional stress transfer between fibers and matrix, by grafting carbon nanotubes on to carbon fibers (in the form of carbon fabric) by two different methods: (1) chemical vapor deposition (CVD) method and (2) a purely chemical method. With the CVD process, carbon nanotubes (CNT) were directly grown on carbon fiber substrate using chemical vapors. For the chemical method, CNT with carboxyl groups were grafted on functionalized carbon fiber via a chemical reaction. The morphology of CNT/carbon fibers was examined by scanning electron microscope (SEM) which revealed uniform coverage of carbon fibers with CNT in both of CVD method and chemical grafting method. CNT-grafted woven carbon fibers were used to make carbon/epoxy composites, and their mechanical properties were measured using three-point bending and tension tests which showed that those with CNT-grafted carbon fiber reinforcements using the CVD process has 11 % higher tensile strength compared to those containing carbon fibers modified with the chemical method. Also, composites with CNT-grafted carbon fibers with chemical method showed 20 % higher tensile strength compared to composites with unmodified carbon fibers. The results of tensile test revealed that both CVD and chemical grafting could significantly improve the mechanical properties of the carbon fiber composites.     

功能化碳纳米管的制备及功能化碳纳米管/尼龙6复合纤维

采用多聚磷酸(PPA)/P₂O₅弱酸体系, 通过傅克反应(Friedel-Crafts reaction)对多壁碳纳米管(MWCNTs)进行功能化改性, 加入己内酰胺后采用原位聚合法制备功能化碳纳米管(F-MWCNTs)/尼龙6(PA6)复合材料, 并熔融纺丝制备复合纤维。通过TEM、TG、DSC、SEM及力学性能测试对复合纤维进行表征。结果表明: 在MWCNTs表面成功地接枝了氨基, F-MWCNTs均匀地分散在PA6基体中, 没有发生团聚现象, 并且与基体具有很好的界面作用; F-MWCNTs的加入, 对复合纤维的熔融温度和结晶度影响不大, 结晶温度有所提高, 并明显提高了复合纤维的热稳定性; 随着F-MWCNTs的加入, 复合纤维的拉伸断裂强度和杨氏模量增加, 当F-MWCNTs质量分数为0.5%时, 拉伸断裂强度和杨氏模量达到最大, 比纯PA6纤维分别提高了45%和208%。     

Macroscopic fibers of well-aligned carbon nanotubes by wet spinning

A simple process to spin fibers consisting of multi-walled carbon nanotubes (CNTs) directly from their lyotropic liquid-crystalline phase is reported. Ethylene glycol is used as the lyotropic solvent, enabling a wider range of CNT types to be spun than previously. Fibers spun with CNTs and nitrogen-doped CNTs are compared. X-ray analysis reveals that nitrogen-doped CNTs have a misalignment of only +/-7.8 degrees to the fiber axis. The tensile strength of the CNT and nitrogen-doped CNT fibers is comparable but the modulus and electrical conductivity of the are lower. The electrical conductivity of both types of CNT fibers is found to be highly anisotropic. The results are discussed in context of the microstructure of the CNTs and fibers.     

Modeling the effect of statistical variations in length and diameter of randomly oriented CNTs on the properties of CNT reinforced nanocomposites

A nano-mechanical model has been developed to calculate the tensile modulus and the tensile strength of randomly oriented short carbon nanotubes (CNTs) reinforced nanocomposites, considering the statistical variations of diameter and length of the CNTs. According to this model, the entire composite is divided into several composite segments which contain CNTs of almost the same diameter and length. The tensile modulus and tensile strength of the composite are then calculated by the weighted sum of the corresponding modulus and strength of each composite segment. The existing micro-mechanical approach for modeling the short fiber composites is modified to account for the structure of the CNTs, to calculate the modulus and the strength of each segmented CNT reinforced composites. Multi-walled CNTs with and without inter-tube bridging have been considered. Statistical variations of the diameter and length of the CNTs are modeled by a normal distribution. Simulation results show that CNTs inter-tube bridging, length and diameter affect the nanocomposites modulus and strength. Simulation results have been compared with the available experimental results and the comparison concludes that the developed model can be effectively used to predict tensile modulus and tensile strength of CNTs reinforced composites.     

改性碳纳米管处理碳纤维的效果表征

采用浓硫酸/浓硝酸氧化处理多壁碳纳米管(MWCNTs),再将氧化后的碳纳米管与硅烷偶联剂(KH560)进行接枝,制备了硅烷偶联剂表面化学修饰的MWCNTs。在此基础上,将改性前后的碳纳米管分散在环氧树脂体系中,涂覆处理碳纤维。研究处理前后碳纤维力学性能和界面性能的变化。通过红外光谱(FTIR)和透射电镜(TEM)分析,表明KH560已成功接枝到多壁碳纳米管上;通过分散性实验证明了改性后的碳纳米管分散性提高;对处理后的碳纤维进行力学性能测试,并用扫描电镜(SEM)观察分析断面形态变化,结果表明,当碳纳米管的含量为0.5%时,改性碳纳米管处理的碳纤维拉伸强度和拉伸模量分别提高23.83%和7.11%,界面性能增强。     

Effects of the carbon nanotube distribution on the macroscopic stiffness of composite materials

Having extremely high stiffness and low specific weight, carbon nanotubes (CNTs) have been known recently as perfect reinforcing fibers in nanotechnology. They can improve the stiffness and strength of nanocomposites by being used as reinforcing elements for example in polymer matrices. The corresponding properties of the fibers and matrix, such as volume fraction and aspect ratio are some of the significant factors in the characterization of mechanical properties of CNT reinforced composites. In recent years, the way in which fibers are distributed inside the matrix, in terms of randomness, has introduced another important factor in characterizing the mechanical properties of such composites. Based on this factor, composites can be classified into two types namely, aligned and randomly distributed. This research has studied the effect of random distribution of fibers in the matrix on the elastic modulus and initial yield stress of the nanocomposite. Therefore, several models of composites, with different distribution of fibers, were considered while holding the volume fractions and aspect ratio constant. As a result, the effect of randomness on the effective modulus of CNT reinforced composites was estimated. The finite element method (FEM), using the MSC.Marc software, was employed to predict the effective modulus of CNT reinforced composites and the results were successfully validated by comparison with the analytical Halpin-Tsai method.