碳纳米管-碳纤维复合改性混凝土力学性能研究

碳纳米管-碳纤维复合增强体(CNTs-CF)是一种在碳纤维(CF)表面引入碳纳米管(CNTs)构筑而成的新型纤维材料。按照利用CNTs-CF作为跨尺度增强组分对混凝土进行改性的思路,制备出五种CNTs-CF体积掺量(0%、0.1%、0.2%、0.3%和0.4%)的碳纳米管-碳纤维复合改性混凝土(CCMC),测试了CCMC的抗压强度、抗折强度、折压比(抗折强度与抗压强度的比值)及破坏形态等性能指标,进而结合扫描电镜(SEM)图像,分析了CNTs-CF对混凝土基本力学性能的增效机理。结果表明：掺加适量的CNTs-CF有利于混凝土抗压强度和抗折强度的提升,并且CNTs-CF在混凝土基体中的体积掺量存在相对最佳值。与未配置CNTs-CF的普通混凝土相比,当CNTs-CF体积掺量为0.3%时,CCMC的抗压强度提高了8.79%,抗折强度提高了27.76%。在本试验的纤维掺量范围内,CCMC的折压比随CNTs-CF体积掺量的增加呈现出递增趋势,提高幅度为8.47%～19.16%。掺入CNTs-CF后,混凝土的脆性破坏特征有所减弱,在受荷失效时,其仍可保持较好的完整性,坏而不散、裂而不断。CNTs-...     

CF-CNTs多尺度增强体的制备及CF-CNTs/环氧树脂复合材料力学性能

利用化学气相沉积(CVD)法在碳纤维(CF)表面生长碳纳米管(CNTs),制备了CF-CNTs多尺度增强体,增强体与环氧树脂(EP)结合得到CF-CNTs/EP复合材料。采用场发射扫描电镜(FESEM)、高分辨透射电镜(HRTEM)等方法研究了不同CVD工艺参数对CF-CNTs多尺度增强体的影响,并研究了不同CVD时间对CFCNTs/EP复合材料力学性能的影响。结果表明:沉积温度为500℃、沉积时间为10min、反应压力为0.02 MPa时,制备得到的多尺度增强体性能最好。CF-CNTs多尺度增强体较未生长CNTs的碳纤维与环氧树脂的浸润性明显提高。在CVD时间为10min时,所得CF-CNTs/EP复合材料的界面剪切强度(IFSS)最大可提高90.6%,层间剪切强度(ILSS)最大可提高24.4%。同时,在制备环氧树脂复合材料过程中碳纤维的不加捻与加捻相比,其ILSS提高了11.3%。     

MWCNTs对环氧树脂及多尺度MWCNTs-碳纤维/环氧树脂复合材料力学性能的影响

通过对胺基化多壁碳纳米管（MWCNTs-NH₂）进行改性,得到改性MWCNTs悬浮液（MWCNTs-NH₂（M））。分别将羧基化MWCNTs （MWCNTs-COOH）和MWCNTs-NH₂（M）分散在环氧树脂（EP）中,采用热熔法制备了多尺度MWCNTs-碳纤维（CF）/EP复合材料。研究了MWCNTs对EP模量、韧性及EP与CF之间界面黏结强度的影响,并分析了MWCNTs与CF上浆剂的作用,评价了多尺度MWCNTs-CF/EP复合材料的力学性能。结果表明：官能团化的MWCNTs可对EP的模量和韧性起到更好的增强作用。MWCNTs接枝的-COOH或-NH₂可与CF上浆剂中的环氧基团发生化学反应,提高EP与CF之间的界面剪切强度。MWCNTs-NH₂（M）对多尺度MWCNTs-CF/EP复合材料力学性能的增强效果优于MWCNTs-COOH,当MWCNTs-NH₂（M）的含量为1wt%时,多尺度复合材料的0°压缩强度、90°压缩强度、弯曲强度、弯曲模量、冲击后压缩强度（CAI）分别提高了16.7%、16.3%、40.9%、30.3%、20.6%。     

加载金属催化剂在碳纤维表面生长多尺度碳纳米管增强体EI北大核心CSCD

用化学气相沉积法在高强度碳纤维表面生长碳纳米管(CNTs)多尺度增强体,研究了加载金属催化剂成分对CNTs生长前后碳纤维强度的影响。结果表明:在500℃金属催化剂成分对还原后催化剂颗粒的形貌和碳纤维的强度影响不大,但是对CNTs的生长速度和碳纤维表面生长CNTs多尺度增强体的强度有显著的影响。高催化效率不仅有利于碳纤维表面CNTs的高效合成,还促进碳纤维表面损伤的修复。Fe-Cu和Ni-Cu催化体系具有较高的催化效率,碳纤维表面催化生长CNTs后其拉伸强度分别提高了12.26%和12.80%。     

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。     

碳纳米管有序排列对碳纤维增强环氧树脂基复合材料低温性能的影响

为了提高碳纤维增强环氧树脂(CF/EP)复合材料在低温(77K)循环条件下的抗微裂纹性能,采用共沉淀法制备了具有良好顺磁性的Fe_3O_4修饰氧化碳纳米管(Fe_3O_4-O—MWCNTs),并研究了Fe_3O_4-O—MWCNTs在环氧树脂(EP)基体中的有序排列对EP及CF/EP复合材料低温性能的影响。结果表明:Fe_3O_4-O—MWCNTs的有序排列可有效提高EP基体的低温力学性能及降低EP基体的热膨胀系数,相对于纯EP,Fe_3O_4-O—MWCNTs改性EP的热膨胀系数降低了41.6%;相对于CF/EP复合材料,Fe_3O_4-O—MWCNTs改性CF/EP复合材料在低温环境下的微裂纹密度降低了56.2%。     

碳纤维增强树脂基复合材料的界面

从碳纤维、树脂基体、界面3个层次对碳纤维增强树脂基复合材料的界面研究进行了综述,重点介绍了碳纤维表面特性表征及改性方法、树脂基体特性及改性方法和界面分析表征手段,由此提出了纤维/树脂界面的研究路线,简要分析了复合材料界面研究的前景与趋势。为了实现纤维/树脂界面的良好匹配,充分发挥碳纤维复合材料的性能优势,需完善界面表征手段、明确界面微观性能与复合材料宏观性能的关系、深化研究界面对复合材料湿热性能及失效模式的影响等。     

CNTs强化碳纤维/环氧复合材料界面过渡层及其对界面性能的影响

采用上浆的方法将碳纳米管(CNTs)引入到碳纤维表面,制备CF/CNTs/环氧多尺度复合材料。相比上浆处理前,复合材料的层间剪切强度及弯曲强度分别提高了13.54%和12.88%。采用力调制原子力显微镜及扫描电镜的线扫描功能对复合材料界面相精细结构进行分析。结果表明:CNTs的引入在纤维和基体间构建了一种CNTs增强环氧树脂的界面过渡层。该界面过渡层具有一定厚度,且其模量和碳元素含量呈梯度分布。在固化成型前对含有CNTs的复合材料进行超声处理,促使碳纤维表面的CNTs向周围树脂中分散,发现复合材料的界面过渡层被弱化,其层间剪切强度及弯曲强度较超声处理前分别下降了7.33%和5.34%,验证了CNTs强化的界面过渡层对于提高复合材料界面性能的重要作用。     

3D打印制备碳纳米管/环氧树脂电磁屏蔽复合材料

采用3D打印技术制备具有连续通孔的环氧树脂基体,利用浸渍工艺将碳纳米管（CNTs）附着于环氧树脂基体孔壁,获得具有优异电性能和电磁屏蔽功能的CNTs/环氧树脂复合材料。研究结果表明,CNTs含量仅为2.86vol%时,CNTs/环氧树脂复合材料电导率高达35 S/m,总电磁屏蔽效能高达39.2 dB（厚度为2.0 mm）。研究表明,CNTs/环氧树脂复合材料对进入其内部电磁波的吸收占总屏蔽效能的98%,表现出吸收屏蔽为主导的电磁屏蔽机制。CNTs/环氧树脂复合材料的弯曲强度和弯曲模量相比环氧树脂基体也有一定的提高。该研究为具有优异电磁屏蔽性能的高分子基复合材料制备提供了新思路和方法。      

碳纳米管浸润剂对碳纤维/环氧树脂界面性能的影响

制备了含碳纳米管(CNTs)的水溶液, 将该水溶液作为浸润剂浸渍碳纤维并进行烘干, 采用扫描电镜(SEM)和原子力显微镜(AFM)研究了CNTs含量及浸润工艺对碳纤维表面CNTs分布的影响, 运用单丝断裂法分析了CNTs浸润剂处理对碳纤维/环氧树脂界面粘结性能的影响和作用机制。结果表明: CNTs可在T700和T300纤维表面黏附, 浸润剂中CNTs含量越高, CNTs在纤维表面含量越高; 对于CNTs含量较低的浸润剂, 采用增加浸润次数的方法, 能有效提高碳纤维表面CNTs的含量和碳纤维表面粗糙度; 经过CNTs浸润剂处理后, 碳纤维/树脂界面处的机械啮合作用增强, 界面粘结强度明显提高, 增幅最高达35.8%。     

Impact behavior and fractographic study of carbon nanotubes grafted carbon fiber-reinforced epoxy matrix multi-scale hybrid composites

Carbon nanotubes are the most promising reinforcement for high performance composites. Multiwall carbon nanotubes were directly grown onto the carbon fiber surface by catalytic thermal chemical vapor deposition technique. Multi-scale hybrid composites were fabricated using the carbon nanotubes grown fibers with epoxy matrix. Morphology of the grown carbon nanotubes was investigated using field emission scanning electron microscopy and transmission electron microscopy. The fabricated composites were subjected to impact tests which showed 48.7% and 42.2% higher energy absorption in Charpy and Izod impact tests respectively. Fractographic analysis of the impact tested specimens revealed the presence of carbon nanotubes both at the fiber surface and within the matrix which explained the reason for improved energy absorption capability of these composites. Carbon nanotubes presence at various cracks formed during loading provided a direct evidence of micro crack bridging. Thus the enhanced fracture strength of these composites is attributed to stronger fiber–matrix interfacial bonding and simultaneous matrix strengthening due to the grown carbon nanotubes.     

Preparation and mechanical properties of carbon nanotube grafted glass fabric/epoxy multi-scale composites

In the present paper, carbon nanotubes (CNTs) were chemically grafted onto surfaces of the amino silane treated glass fabric by a novel chemical route for the first time to create 3D network on the glass fibers. The chemical bonding process was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. The glass fabric/CNT/epoxy multi-scale composite laminates were fabricated with the CNT grafted fabrics using vacuum assisted resin infusion molding. Tensile tests were conducted on fabricated multi-scale composites, indicating the grafting CNTs on glass fabric resulted a decrease (11%) in ultimate tensile strength while toughness of the multi-scale composite laminates were increased up to 57%. Flexural tests revealed that the multi-scale composite laminates prepared with CNT grafted glass fabric represent recovering after first load fall. The interfacial reinforcing mechanisms were discussed based on fracture morphologies of the multi-scale composites.     

羧基化多壁碳纳米管改性洋麻纤维对其环氧树脂复合材料界面性能的影响

植物纤维增强复合材料正广泛应用于生活中各领域,但亲水性增强体与疏水性基体之间界面不相容的问题限制了复合材料的力学性能,本论文通过羧基化碳纳米管(c-MWCNTs)改性洋麻纤维,探究洋麻纤维/环氧树脂复合材料的界面改善机制。首先利用水和NaOH对洋麻纤维进行预处理,通过观测纤维直径变化、红外光谱图和纤维束断裂强度变化,探讨不同预处理方式对c-MWCNTs接枝洋麻纤维的效果影响;然后使用含量分别为0.5wt%、1wt%和3wt%的c-MWCNTs改性洋麻纤维,通过单纤维抽拔实验,探讨洋麻纤维/环氧树脂复合材料的界面剪切强度(IFSS)变化。结果表明,与原洋麻纤维和水预处理过的洋麻纤维相比,经过NaOH处理后的洋麻纤维,直径变化幅度和纤维束断裂强度降低幅度最小,复合材料的尺寸稳定性较高;通过单纤维抽拔实验证明,洋麻纤维/环氧树脂复合材料的界面剪切强度逐渐升高,但是有效性逐渐降低,当c-MWCNTs质量分数为0.5wt%时,c-MWCNTs处理洋麻纤维的有效性最高,达到45.09%;洋麻纤维/环氧树脂复合材料的界面性能得到改善,c-MWCNTs的存在增强了纤维与树脂基体间的机械锁结作用。     

Interlaminar properties of carbon fiber composites with halloysite nanotube-toughened epoxy matrix

Halloysite nanotubes (HNTs), which are geometrically similar to multi-walled carbon nanotubes, can improve the impact strength of epoxy substantially, according to our previous work [1]. Using a HNT-toughened epoxy as the matrix, a set of hybrid composites was prepared with carbon fiber-woven fabrics. The interlaminar properties of the composites were investigated by a short-beam shear test, a double-cantilever-beam test and an end-notched flexure test. The results showed that the addition of HNTs to the composites improved the interlaminar shear strength and the fracture resistance under Mode I and Mode II loadings greatly. The morphological study of the hybrid composites revealed that HNTs were non-uniformly dispersed in the epoxy matrix, forming a unique microstructure with a large number of HNT-rich composite particles enveloped by a continuous epoxy-rich phase. A study of the fracture mechanism uncovered the important role of this special morphology during the fracturing of the hybrid composites.     

Improved interfacial properties of carbon fiber/epoxy composites through grafting polyhedral oligomeric silsesquioxane on carbon fiber surface

Carbon fibers were grafted with a layer of uniform octaglycidyldimethylsilyl POSS in an attempt to improve the interfacial properties between carbon fibers and epoxy matrix. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analysis were performed to characterize the carbon fibers. AFM results show that the grafting of POSS significantly increased the carbon fiber surface roughness. XPS indicates that oxygen-containing functional groups obviously increased after modification. Dynamic contact angle analysis shows that the surface energy of modified carbon fibers is much higher than that of the untreated ones. Results of the mechanical property tests show that interlaminar shear strength (ILSS) increased from 68.8 to 90.5 MPa and impact toughness simultaneously increased from 2.62 to 3.59 J.     

The effect of surface treatment on the interfacial properties in carbon fibre/epoxy matrix composites

Carbon fibres with different degrees of surface oxidation, as well as epoxy-sized fibres, were used to prepare epoxy composites in order to compare the effects of the fibres surface chemistry on the interfacial properties. X-ray photoelectron spectroscopy, water vapour adsorption measurements and contact angle examination were applied to characterize the carbon fibre surfaces. A correlation was found between the content of primary adsorption sites on the fibre surface and interlaminar shear strength (ILSS) of the composites. Higher values of ILSS obtained for the oxidized fibres containing composites are proposed to be due to the higher concentration of carboxylic groups created on the oxidized fibres surface and to the creation of chemical bonds at the fibre/epoxy matrix interface. Enthalpy of cure, reaction peak temperature and glass transition temperature of the composites were determined by differential scanning calorimetry.     

Effect of new epoxy matrix for T800 carbon fiber/epoxy filament wound composites

A new epoxy resin matrix with good adherence to T800 carbon fibers (T800 CFs) in filament winding was developed by addition of hardener and resin diluter. Interfacial behavior of the T800 CF/epoxy composites was analyzed according to the Naval Ordnance laboratory (NOL) ring test, short-beam-shear test and fracture surface observation. Meanwhile, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used in analysis of the interfacial behavior. The interfacial properties of the T800 CF/epoxy filament wound composites were improved by optimizing the matrices through increasing the toughness and reducing the viscosity, which is an important factor in influencing the wettability of T800 CFs. The Interlaminar shear strength (ILSS) of the unidirectional T800 CF/epoxy composites and the tensile strength of NOL-ring in this work reached to 123 and 2570 MPa, respectively. Also, the interfacial adhesion was much improved by the chemical reactions between the new matrix and the sizing on the T800 CFs.     

基于微波等离子体方法生长的纳米碳对碳纤维/环氧树脂复合材料界面性能的影响

为了提高复合材料的界面性能,采用微波等离子体（MPECVD）方法,通过控制工艺参数,在碳纤维（CF）表面生长结构形貌各异的纳米碳,将其引入CF/环氧树脂（EP）复合材料界面微区。采用FESEM研究了不同MPECVD工艺参数对沉积纳米碳结构形貌的影响,采用单纤维破碎实验研究了纳米碳形貌对CF/EP复合材料的界面性能影响,探讨了纳米碳-CF/EP复合材料界面微观结构与其界面性能之间的关系。结果表明：随着MPECVD沉积功率的变化,沉积的纳米碳结构形貌变化较大。当沉积功率为700 W时,制备得到的多尺度纳米碳-CF/EP复合材料界面性能最高,界面剪切强度（IFSS）达到112.38 MPa,提高了118.85%。     

Effect of epoxy coatings on carbon fibers during manufacture of carbon fiber reinforced resin matrix composites

The changes in oxygen and nitrogen during manufacture of the carbon fiber reinforced resin matrix composites were measured using the X-ray photoelectron spectroscopy method. The effects of the change in oxygen and nitrogen on the strength of the carbon fibers were investigated and the results revealed that the change of the tensile strength with increasing heat curing temperature was attributed to the change in the surface flaws of the carbon fibers because the carbon fibers are sensitive to the surface flaws. The effect of the surface energy that was calculated using Kaelble’s method on the strength of the carbon fibers was investigated. Furthermore, the surface roughness of the carbon fibers was measured using atom force microscopy. The change trend of roughness was reverse to that of the strength, which was because of the brittle fracture of the carbon fibers.