3D printed aluminum matrix composites with well-defined ordered structures of shear-induced aligned carbon fibers

Carbon fiber reinforced aluminum composites with ordered architectures of shear-induced aligned carbon fibers were fabricated by 3D printing.The microstructures of the printed and sintered samples and mechanical properties of the composites were investigated.Carbon fibers and aluminum powder were bonded together with resin.The spatial arrangement of the carbon fibers was fixed in the aluminum matrix by shear-induced alignment in the3D printing process.As a result,the elongation of the composites with a parallel arrangement of aligned fibers and the impact toughness of the composites with an orthogonal arrangement were 0.82%and 0.41 J/cm^(2),respectively,about 0.4 and 0.8 times higher than that of the random arrangement.

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.

Damping capacity of amorphous carbon fiber/aluminum matrix composites at room temperature

The influence of volume fraction on damping capacities at room temperature for amorphous carbon fiber reinforced aluminum matrix composites was investigated.At room temperature,the dislocation damping is the primary damping mechanism.Meanwhile,the dislocation damping exhibits dynamic hysteresis at low strain amplitudes and static hysteresis at high strain amplitudes.Moreover,the damping capacity is rather sensitive to the volume fraction.Compared to unreinforced aluminum alloy,the additions of amorphous carbon fibers into the aluminum matrix can improve damping capacity below the volume fraction of 30%,whereas worsen above the volume fraction of 40%.

Improved multi-orientation dispersion of short carbon fibers in aluminum matrix composites prepared with square crucible by mechanical stirring

In order to improve the strength of short carbon fibers reinforced aluminum matrix(Csf/Al)composite,the dispersion of short carbon fibers with multi-orientation was controlled with a square crucible by mechanical stirring.The three-dimensional flow field models of liquid aluminum melt in the square/round crucibles were established and calculated,and the results were compared.The calculated results show that turbulent flow could be induced both in the square and round crucible,while the non-axisymmetric structure of the square crucible results in higher turbulent kinetic energy in the melt.Therefore,the uniformity and multi-orientation dispersion of the short fibers can be improved by the intensive turbulent flow in the square crucible,which will be increased by increasing the rotational velocity.The distribution of the short carbon fibers in the aluminum matrix prepared under different rotation velocities in square crucible was experimentally investigated.With the increase of stirring velocity,the multi-orientation dispersion of the short fibers in the composites increased gradually.The experimental results are consistent with the calculation results.The tensile testing results show that the strength of the Csf/Al composite can reach 172 MPa when the rotational velocity is 1000 rpm,and it is 48.3%higher than that prepared by the round crucible under the same conditions,which results from the improved multi-orientation dispersion of short carbon fibers in aluminum matrix.

Comparative study on the interface and mechanical properties of T700/Al and M40/Al composites

T700/Al and M40/Al composites were fabricated by squeeze casting technology, and their interface and mechanical properties were investigated comparatively. The results showed that both of the composites were dense, and the fibers were distributed uniformly in aluminum matrix. Aluminum carbide （Al4C3） was observed on the interface of the two carbon fiber-reinforced aluminum （Cf/Al） composites. There was little Al4C3 with a length of 300-500 nm and a width of 30-60 nm in the M40/Al composite, whereas there was a great deal of Al4C3 with a length of 200-400 nm and a width of 100-200 nm in the T700/Al composite, due to a higher graphitization of M40Cf than T700Cf. The M40/Al composite showed a much higher tensile strength than the TT00/Al composite, and it was related to interracial bonding between carbon fibers and aluminum matrices.

Self-lubricating bidirectional carbon fiber reinforced smart aluminum composites by squeeze infiltration process

Self-lubrication is one of the smart material properties required for producing components with enhanced wear resistance and low coefficient of friction.Bidirectional(BD)satin weave polyacrylonitrile(PAN)based carbon fiber(Cf)fabric preform was successfully infiltrated with Al 6061 alloy by squeeze infiltration process.The infiltrated composite shows uniform distribution of carbon fibers in the matrix with the elimination of porosities,fiber damage and close control on the formation of deleterious aluminum carbide(Al4C3)phase.Cf/Al composite exhibits remarkable wear resistance compared to unreinforced alloy due to the formation of self-lubricating tribolayer on the pin surface,which intercepts the contact of matrix metal to counter surface.The BD carbon fiber enhanced the hardness and compressive strength of the composite by restraining the plastic flow behavior of matrix.High resolution transmission electron microscopy shows the presence of Al2O3 and MgAl2O4 spinel,confirmed by EDS and SAD pattern,at the composite interface.The composite shows a lower density of 2.16 g/cm^3 which is a major ad vantage for weight reduction compared to the monolithic alloy(2.7 g/cm^3).

Bending mechanical property and failure mechanisms of woven carbon fiber-reinforced aluminum alloy composite

Copper-coated woven carbon fiber-reinforced aluminum alloy composite was prepared by spark plasma sintering （SPS）. Microstructure, three-point bending mechanical property, and the failure mechanisms of the composite were investigated. Microstructure observation shows that the carbon fibers bond compactly with matrix alloy. Compared with the matrix aluminum alloy, the bending strength, ductility, fracture energy, and cracking resistance of the composite are evidently improved. Microstructure analyses reveal that the high specific strength of carbon fibers and transfer of stress from matrix alloy to carbon fibers are responsible for the increase of the composite bending strength. The expanding of cracks is restrained, and cracking resistance of the composite is improved by adding woven carbon fiber. Attributed to the carbon fibers＇ debonding, cracks deflection, and multipath propagation mechanisms, the fracture energy of the composite increases.

Effect of CeO_2 on Corrosion Resistance of C_f/2024 Composites

The corrosion resistance of 2024 alloys and Cf/2024 composites in 3.5% NaCl aqueous solution at normal temperature was studied by IM6e electrochemical measurement system, scanning electron microscopy(SEM) and electron diffraction scanning(EDS). The results indicate that CeO2 can raise the corrosion potential of the 2024 alloys and the Cf /2024 composites, prevent the pitting on the alloys and composites surface, and restrain the reaction of divided hydrogen, refine grain, and make the surface more even.

Effect of coating thickness on microstructures and mechanical properties of C/Cu/Al composites

The different copper coatings with thickness varying from 0.3μm to 1.5μm were deposited on carbon fibers using either electroless plating or electroplating method. The coated fibers were chopped and composites were fabricated with melting aluminum at 700℃. The effect of the copper layer on the microstructure in the system was discussed. The results show that the copper layer has fully reacted with aluminum matrix, and the intermetallic compound CuAl2 forms through SEM observation and XRD, EDX analysis. The results of tensile tests indicate that composites fabricated using carbon fibers with 0.7-1.1μm copper coating perform best and the composites turn to more brittle as the thickness of copper coating increases. The fracture surface observation exhibits good interface bonding and ductility of the matrix alloy when the thickness of copper coating is about 0.7-1.1μm.

轻木夹芯/碳纤维复合材料结构后推构型无人机机身设计与分析

设计了一款后推构型轻木夹芯/碳纤维复合材料结构无人机机身,完成了机身气动外形设计、流场分析和内部结构设计。建立了机身结构有限元模型,完成了结构刚度校核。编写子程序,将3D Hashin失效准则嵌入计算模型,基于三类失效模式构建极限状态函数g(x),对机身结构进行了强度及稳定性校核。采用等步长施加超设计载荷,预测了结构的初始损伤位置及模式。对机身蒙皮铺层方案进行了优化设计,采用g(x)函数对更改铺层方案后的结构性能进行了评估。研究结果表明:着陆工况和最大飞行速度工况的机身蒙皮表面压强最大值均在机头整流罩区域。两种工况的极限状态函数g(x)均大于0,最大位移分别为3.076 mm和2.92 mm,机身结构满足刚度、强度和稳定性要求。对着陆工况施加1.17倍设计载荷时,油料舱下壁板轻木芯材发生压缩分层初始损伤。机身结构失稳发生于侧面蒙皮,提高45°铺层占比可提高蒙皮的稳定性。玻纤蒙皮铺层优化后,在质量不变的条件下,结构稳定性裕度提高了7.2%。

双辊铸轧工艺制备连续碳纤维增强铝基复合材料的研究

连续碳纤维增强铝基(CCF/Al)复合材料具有高比强度、低密度、良好的传热性以及低热膨胀系数等诸多优良的特性,在航空材料、汽车制造、电子设备和工业生产等领域均具有广阔的应用前景。对连续碳纤维表面涂层的制备方法进行了讨论,并总结了近年来CCF/Al复合材料的主要制备工艺、重要研究成果以及存在的问题;重点阐述了采用双辊铸轧工艺制备CCF/Al复合材料的研究结果,具体包括搭建的实验设备、改性后碳纤维的性能、所制备复合材料的组织结构及强化机理;讨论了该工艺目前存在的主要问题,并对其发展前景进行了展望。

CFRP-铝合金复合管高强混凝土短柱轴压性能研究

为研究CFRP-铝合金复合管混凝土构件的轴压性能,进行了12根短柱试件的轴向压缩试验,主要研究参数为CFRP层数。试验结果表明:复合管混凝土试件出现了多处外凸鼓曲以及对应位置混凝土被压溃的破坏形态,而空复合管试件发生了局部内凹屈曲破坏;试件轴压承载力随CFRP层数的增加而增大,且复合管混凝土试件的承载力提高幅度高于相应的空复合管试件的提高幅度。对各部分的承载力贡献比例进行分析,发现复合管混凝土试件中混凝土的承载力贡献比例超过70%,且承载力贡献度随CFRP层数的增加而提高。提出了CFRP-铝合金复合管混凝土构件的轴压承载力计算公式。

碳纤维增强铝基复合材料界面隔离层研究进展

碳纤维增强铝基复合材料是最有应用前景的新型复合材料之一。从碳纤维增强体及其特点出发,分析了碳纤维增强铝基复合材料存在的问题与挑战,提出在相界处引入陶瓷隔离层以改善润湿性并抑制脆性界面相生成的思路。列举了以化学气相沉积、直接原位反应、熔盐反应等制备碳化物陶瓷隔离层的方法。其中,熔盐反应以其稳定的化学反应、细小的晶粒尺度、可控的隔离层厚度等优势备受青睐,是改善碳纤维增强铝基复合材料界面组织与性能的有效方案。

表面构型对输电导线覆冰碰撞特性的影响分析

导线结冰严重影响着电网运行安全,局部碰撞系数是表征输电导线覆冰增长速率的关键指标,以往对传统钢芯铝绞线或其简化圆柱模型的覆冰增长特性进行了分析,碳纤维复合芯导线(Aluminum Conductor Composite Core,ACCC)作为一种发展迅速的新型导线,其局部碰撞系数和覆冰增长过程鲜有研究。首先基于商用有限元软件Fluent实现了对覆冰增长数值模拟,并通过与模拟试验结果对比,验证了仿真方法的有效性。随后,利用经过验证的数值模拟方法,对ACCC模型和简化的圆导线模型的覆冰增长特性进行了对比研究,模拟得到了二者表面的液滴碰撞系数分布,讨论了不同的雨滴中值直径和风速变化对碰撞系数的影响,获取了ACCC模型的结冰冰形。结果表明:风速低时ACCC模型的局部碰撞系数显著小于圆模型,覆冰初期,冰形受导线表面构型影响十分显著;当导线表面被覆冰完全包裹后,圆模型冰形比ACCC模型冰形阻力系数整体低15.3%,且在多个风攻角下呈现驰骋不稳定性。研究结果对于获取ACCC覆冰增长特性,了解不同表面构型导线覆冰致灾机理具有重要价值。

基于光纤传感技术的多股碳纤维复合芯导线隐蔽性缺陷检测

为解决大容量、大跨越输电用碳纤维导线由于隐蔽性缺陷无法检出而导致频繁断线的问题,提出了一种基于光纤传感技术的多股碳纤维复合芯导线隐蔽性缺陷检测方法。该方法通过搭建导线运行环境并模拟导线运行工况,采用基于分布式光纤布里渊散射的时域反射技术,检测碳纤维导线的温度和应变分布情况,并结合光时域反射技术,检测碳纤维导线中光纤的损耗情况。经过综合对比分析,获取可表征多股碳纤维缺陷隐蔽性缺陷的光纤温度、应变、损耗等信号特征量,并构建神经网络模型,将各信号特征量作为模型输入,通过模型训练确定模型内各权系数,使其能够有效地检测多股碳纤维复合芯导线隐蔽性缺陷。实验结果表明,该方法可有效获取各类光纤信号特征量,并且能够准确地检测各类导线隐蔽性缺陷,具有重要的实际应用价值。

碳/铝复合材料界面Al_(4)C_(3)相的形成与调控研究进展

石墨烯、碳纳米管和碳纤维等碳材料作为铝基复合材料的增强体时,其界面润湿性差、与Al基体结合弱等缺点限制了其增强效果。利用C与Al反应使界面黏接形式转变为部分反应结合的形式,可有效提升碳/铝(C/Al)界面强度及其载荷与功能传递的效率。然而,高温下C/Al界面反应易生成大量脆性Al_(4)C_(3),且会损伤增强体。针对C/Al界面Al_(4)C_(3)的调控,本文首先介绍了其形成机制、对C/Al复合材料界面结合和性能的作用,随后从碳增强体表面涂层、纳米颗粒修饰、Al基体合金化,以及复合制备、热加工与处理工艺优化等方面,综述了Al_(4)C_(3)生成量与形貌的控制研究及效果,最后展望了C/Al复合材料界面与性能的研究方向,以期通过碳增强体跨尺度设计与界面构型控制,挖掘石墨烯、碳纳米管和碳纤维增强Al基体的最大潜能。

循环盐雾环境中碳纤维复合材料-6082铝合金螺栓连接结构中铝合金的腐蚀行为

采用循环盐雾加速腐蚀试验,通过腐蚀速率测试、腐蚀形貌观察和电化学方法研究了碳纤维复合材料-6082铝合金螺栓连接结构中6082铝合金的腐蚀行为。结果表明:与碳纤维复合材料连接后,6082铝合金的腐蚀速率是未连接试样的13倍,铝合金与裸露的碳纤维接触处的腐蚀最严重。随着腐蚀时间的延长,铝合金的腐蚀电位逐渐下降,腐蚀电流密度增大,耐蚀性减弱,铝合金表面的腐蚀产物逐渐形成致密和疏松的双层结构。

基于分布式光纤传感技术的碳纤维复合芯导线缺陷识别方法

研究基于分布式光纤传感技术的碳纤维复合芯导线缺陷识别方法,有效采集导线应变信息,提升导线缺陷识别效果。创新性地根据偏振光时域反射原理,利用分布式光纤传感技术采集碳纤维复合芯导线应变信息;通过经验小波变换提取应变信息特征;利用自适应t分布改进的麻雀搜索算法,优化径向基神经网络权值,确定最佳径向基神经网络结构;按照邻近原则聚类应变信息特征,输出导线缺陷识别结果。实验证明:有无扰动时,该方法均可有效采集碳纤维复合芯导线应变信息,抗干扰效果较优;该方法可有效提取并聚类应变信息特征,精准识别导线缺陷。

小型履带变轨吊装车用碳纤维复材制备工艺优化

为了提升小型履带变轨吊装搬运车用碳纤维复合材料的力学性能,采用不同的阳极氧化工艺对2024铝合金进行了预处理,对比分析了不同阳极氧化工艺下碳纤维复合材料的力学性能。结果表明,弯曲强度从高至低顺序为阳极氧化工艺D、阳极氧化工艺C、阳极氧化工艺B、阳极氧化工艺A;剪切强度从高至低顺序为阳极氧化工艺C、阳极氧化工艺B、阳极氧化工艺D、阳极氧化工艺A;冲击强度从高至低顺序为阳极氧化工艺C、阳极氧化工艺D、阳极氧化工艺B、阳极氧化工艺A。适宜的工艺为阳极氧化工艺C,此时铝合金表面氧化孔均匀、孔径适宜。

基于与碳纤维导线匹配的绝缘子耐热研究

为了确保碳纤维复合芯导线在线路增容改造后的安全可靠运行,先从理论上计算出与导体温度对应的复合绝缘子高压端芯棒端部温度,再通过试验检验悬垂复合绝缘子与导线之间增设1片瓷绝缘子的隔热效果,然后叠加瓷绝缘子的金属球窝温升和金属球窝在太阳下的暴晒温度,发现增设1片瓷绝缘子无法确保复合绝缘子芯棒的机械性能,应采用瓷(玻璃)绝缘子串。