分散方法对低含量碳纳米管玻纤/环氧层板性能的影响

采用超声波振荡与超声波破碎两种分散方法制备了低含量碳纳米管(CNTs)增强的环氧树脂, 研究了CNTs对树脂流变特性、 固化特性和力学性能的影响。进一步采用该树脂体系通过真空灌注工艺(VARIM)制备了CNTs含量为0.01%的CNTs-玻璃纤维/环氧树脂复合材料层板, 研究了两种分散方式下CNTs对复合材料层板力学性能的影响和CNTs的增强机制。结果表明: 超声波破碎分散使CNTs长度变短, 分散性更好, 与超声波振荡分散方式相比, CNTs对树脂增黏效果和树脂固化反应的影响更明显。采用双真空灌注工艺, 两种超声波分散方式下CNTs均提高了复合材料的弯曲性能、 层间剪切性能和树脂与纤维的粘结强度, 而单真空灌注工艺下CNTs的增强效果不明显, 说明受纤维过滤作用的影响, 选择合适的灌注工艺和CNTs分散方式, 低含量CNTs可实现对灌注工艺复合材料层板的增强。     

快速固化环氧树脂及其碳纤维/环氧复合材料性能

采用双酚A型环氧树脂（DGEBA）、改性咪唑（MIM）及改性脂肪胺（MAA）研制快速固化树脂体系。分别利用DSC和流变仪测试了树脂体系的固化特性与流变行为,优选了树脂配方。采用真空辅助树脂灌注工艺（VARIM）制备了快速成型的碳纤维/环氧复合材料层板,考察了层板的成型质量和力学性能,并与常规固化的层板性能进行了对比。结果表明：采用优选的树脂配方,120 ℃下树脂在5 min内固化度达95%,碳纤维/环氧复合材料层板成型固化时间可控制在13 min以内,固化度达95%以上,并且没有明显缺陷;与常规固化相比（固化时间大于2 h）,快速固化碳纤维/环氧复合材料层板的弯曲性能和耐热性能降低幅度较小。     

L形层板真空袋成型缺陷的实验研究

采用真空袋阳模成型法在不同条件下制备了90°的L形玻纤单向布/环氧树脂层板, 对层板不同位置处纤维密实和缺陷状况进行了研究, 考察了成型过程主要工艺条件对缺陷的影响规律。结果表明, 富树脂、 孔隙、 厚度分布不均和纤维屈曲变形是L形层板中主要的缺陷类型, 加压时机、 层板尺寸、 铺层方式以及边界条件对纤维密实和缺陷的形成都有重要的影响。对以上各种缺陷的产生机制进行了初步分析: 剪切流动的存在导致层板厚度分布不均匀而且出现富树脂区; 纤维的屈曲变形是由于轴向受压缩力; 本文实验条件下孔隙的主要来源是夹杂空气。研究结果对热压工艺中缺陷的预测与控制以及工艺参数的优化具有重要的指导意义。      

复合材料变厚层板热压成型缺陷类型与成因实验研究

采用热压机工艺与热压罐工艺两种成型方法制备了玻璃纤维/环氧 648 变厚度层板 , 研究了两种工艺下缺陷的形成机制及铺层方式和变厚梯度对缺陷程度和分布的影响。结果表明 : 纤维分布不均、 富树脂、 分层是主要缺陷类型 , 其中纤维分布不均由树脂二维流动引起 , 并与纤维不连续区、 纤维层渗透特性以及外压的均匀性有关; 富树脂主要是纤维的不连续性造成的 ; 而分层缺陷与纤维分布和热膨胀各向异性紧密相关。研究结果对变厚度复合材料层板的缺陷消除和成型质量控制有重要的指导意义。      

热压罐零吸胶工艺树脂压力在线测试及其变化规律

针对碳纤维缎纹布/环氧914预浸料热压罐零吸胶工艺,采用热压成型过程树脂压力在线测试系统监测树脂压力的大小与分布,分析了真空、外加气压对树脂压力的作用规律,通过显微观察研究了真空及外加气压对孔隙缺陷的影响。实验结果表明,所采用的在线测试系统可以定量分析真空在铺层内的作用程度和树脂压力的变化;零吸胶工艺树脂承担了大部分外压且沿层板厚度及面内方向分布均匀;真空通过铺层内的气路通道排出夹杂空气,其作用程度受到树脂黏流状态和铺层密实程度的影响;不同压力条件下复合材料层板孔隙状况与树脂压力的测试结果相吻合。     

玻璃纤维织物/聚苯硫醚粉叠层模塑工艺与性能

研究聚苯硫醚(PPS)树脂粉与玻璃纤维织物(GF)叠层模塑(粉末工艺)制复合材料的工艺与性能。测试各种工艺条件制GF/PPS层板的弯曲力学性能、动态力学性能,用扫描电镜(SEM)探查树脂对纤维的浸渍及纤维/基体的界面粘合情况。SEM分析结果表明,粉末工艺制得的PPS基复合材料呈现高的力学性能,是由于树脂对纤维的均匀浸渍和良好的纤维/基体的界面粘合。熔前热压、高温成型、退火处理是粉末工艺制高质量GF/PPS层板的工艺要点。      

炭纤维复合材料共固化液体成型工艺及层间性能研究

采用共固化液体成型工艺制备了炭纤维/环氧树脂基复合材料层板,分析了层板的密实和两种树脂的相互扩散情况,采用Ⅰ型层间断裂韧性(能量释放率GⅠC)和短梁抗剪强度研究了共固化液体成型层板的层间性能,并与预浸料成型层板和液体成型层板进行了比较。进一步研究了共固化层板中预浸料/液体成型层界面处的纤维取向对GⅠC的影响。结果表明:所制备的共固化液体成型层板,层内密实程度高、层间富树脂区不明显,预浸料/液体成型层的层间处两种树脂有一定程度的相互扩散;受界面处树脂相互扩散的影响,共固化层板的层间断裂韧性处于预浸料层板、液体成型层板的平均水平,而层板的短梁抗剪强度由性能较低的一方决定;预浸料/液体成型层界面处的纤维取向对GⅠC有明显影响,其中[45/90]的情况有着较高的抵抗开裂和裂纹扩展的能力。     

真空辅助树脂灌注工艺成型泡沫夹芯结构工艺设计与控制

采用无屈曲织物(NCF)、 CYCOM^® 890 RTM树脂体系和聚甲基丙烯酰亚胺(PMI)泡沫以及真空辅助树脂灌注成型工艺(VARI)成型泡沫夹芯复合材料平板, 结合力学性能测试和微观结构分析等手段研究了成型过程中抽胶对夹芯板界面质量以及纤维体积分数的影响, 分析产生的缺陷类型及原因, 优化了工艺参数。结果表明: 抽胶有利于提高泡沫夹芯板的纤维体积分数和力学性能, 在100～120 ℃温度范围内进行30 min的抽胶, 工艺稳定, 层间剪切强度和弯曲强度显著提高。     

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。      

多壁碳纳米管对Ti-碳纤维/反应型聚酰亚胺超混杂层板力学性能的影响

为了改善Ti/反应型聚酰亚胺（PMR）树脂界面的黏结强度,从而提高Ti-碳纤维（CF）/PMR超混杂层板的力学性能,本文探究了添加多壁碳纳米管（MWCNTs）对Ti-CF/PMR超混杂层板力学性能的影响。将不同质量分数（0wt%、2.5wt%、5.0wt%和7.5wt%）的MWCNTs利用超声分散法均匀分散于PMR树脂中,随后进行Ⅰ型断裂韧性试验,探究添加MWCNTs对Ti-CF/PMR超混杂层板界面性能的影响,最后选取最优含量的MWCNTs同时添加到PMR胶层和CF/PMR树脂中,并进行弯曲试验,探究添加MWCNTs对Ti-CF/PMR超混杂层板力学性能的影响。通过SEM观察和分析了相应的失效模式和增强机制。结果表明:当MWCNTs含量为5.0wt%时,Ⅰ型层间断裂韧性提高了74%;同时添加5.0wt% MWCNTs于PMR胶层和CF/PMR复合材料树脂中,Ti-CF/PMR超混杂层板的弯曲性能较未添加MWCNTs提高了42%。这是由于MWCNTs在PMR胶层和CF/PMR树脂中的分布均匀性较高,且能分散并承受界面层转移到纤维层的载荷,并利用自身拔出、断裂、桥接、脱黏来吸收并消耗断裂能量,进一步提升Ti-CF/PMR超混杂层板的弯曲性能。      

Effect of rapid curing process on the properties of carbon fiber/epoxy composite fabricated using vacuum assisted resin infusion molding

Long processing cycle makes vacuum assisted resin infusion molding (VARIM) only suitable for low and medium volumes of production, and shortening of curing time is critical to improving the processing efficiency of automotive composite parts. In this paper, unidirectional carbon fiber reinforced composite laminates were fabricated by VARIM. Three different processes (namely quick, quick-post and preheating) were employed, in which a kind of rapid curing epoxy resin is used. The preheating of mold and fiber was conducted to shorten the filling time compared with that of quick process. Quick-post process with a post cure stage was investigated to verify the composite properties fabricated by quick process. The cycle time was 16 min for preheating process, about 30% shorter than that of quick process, simultaneously, flexural strength and interlaminar shear strength (ILSS) were respectively improved by 29% and 7% compared with those of quick process. The non-uniformity of mechanical properties at different positions along resin flow direction under preheating process was found, but the processing quality of composite was good. The preheating process is confirmed to be suitable for the improvement of processing efficiency of VARIM with good mechanical properties. In addition, the composite fabricated by quick-post process has better mechanical properties, which is attributed to the alleviation of residual stress during post curing process.     

Influence of the functionalization of carbon nanotubes on calendering dispersion effectiveness in a low viscosity resin for VARIM processes

The use of a three roll machine to disperse nanoreinforcements in polymer matrix has been proved as an alternative to chemical routes of dispersion. Nevertheless, the degree of dispersion achieved depends on the nanoreinforcement type and the sequences used in the calendering process. This research work focuses in the evaluation of the differences in the dispersion effectiveness of functionalized and non-functionalized carbon nanotubes (CNTs) in an epoxy resin. This aspect has influence not only on the final properties of the nanocomposites but also on the infiltration process due to changes in the rheological behavior and possible filtering of bigger aggregates. Samples of both types of nanoreinforcements up to percentages of 0.5% in weight were characterized using several techniques before and after the curing stage to evaluate variations in the dispersion of the nanoreinforcement and in the final properties of the two types of nanocomposites. The possibility of using CNT/epoxy mixtures as matrix of multiscale composites has been also evaluated fabricating panels by vacuum assisted resin infusion molding (VARIM).     

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.     

Influence of the functionalization of carbon nanotubes on calendering dispersion effectiveness in a low viscosity resin for VARIM processes

The use of a three roll machine to disperse nanoreinforcements in polymer matrix has been proved as an alternative to chemical routes of dispersion. Nevertheless, the degree of dispersion achieved depends on the nanoreinforcement type and the sequences used in the calendering process. This research work focuses in the evaluation of the differences in the dispersion effectiveness of functionalized and non-functionalized carbon nanotubes (CNTs) in an epoxy resin. This aspect has influence not only on the final properties of the nanocomposites but also on the infiltration process due to changes in the rheological behavior and possible filtering of bigger aggregates. Samples of both types of nanoreinforcements up to percentages of 0.5% in weight were characterized using several techniques before and after the curing stage to evaluate variations in the dispersion of the nanoreinforcement and in the final properties of the two types of nanocomposites. The possibility of using CNT/epoxy mixtures as matrix of multiscale composites has been also evaluated fabricating panels by vacuum assisted resin infusion molding (VARIM).     

Damping characteristics of nanoclay filled hybrid laminates during medium velocity impact

The objective of this paper is to study the vibrational damping characteristics during medium velocity impact of nanoclay filled glass fiber reinforced epoxy hybrid laminates. A series of laminates with varying degree of nanoclay concentration (0–5 wt.%) and fiber weight fraction (25–75 wt.%) were prepared by vacuum assisted resin infusion molding (VARIM) method. The laminates were subjected to medium velocity projectile impact using in-house built gas gun set-up and the ballistic limit of laminates series was determined. The result indicated that during impact, the laminate undergoes vibrational damping. This damping property is a function of fiber weight fraction and orientation, nanoclay concentration and nanocomposite structure. A 42% increase of ballistic limit was observed for 5 wt.% nanoclay filled hybrid (50 wt.% fiber) when compared with unfilled composite. Structural and modal analysis of hybrids showed that the increased ballistic limit of nanoclay filled hybrids is due to the nanocomposite structure and improved damping and fracture properties.     

VARI工艺成型纤维增强树脂复合材料层合板厚度和纤维体积分数的影响因素

分析了影响真空辅助成型技术（VARI）工艺成型复合材料的纤维体积分数和厚度均匀性的关键因素,即VARI成型工艺的树脂流动控制形式、纤维预制体状态、织物状态、树脂黏度,通过试验分析了各因素对VARI成型复合材料厚度和纤维体积分数的影响。试验结果表明,采用HFVI（high fiber-volume vacuum infusion）工艺、BA9914树脂及真空处理后的U3160单向机织物成型的纤维增强树脂复合材料层合板,其纤维体积分数和厚度均匀性能够接近预浸料/热压罐成型的复合材料制件的水平。     

Resin infusion analysis of nanoclay filled glass fiber laminates

This paper focuses on the resin flow characteristics of nanoclay filled glass fiber laminates processed by Vacuum Assisted Resin Infusion Molding (VARIM). Laminates with varying quantities of nanoclays (0–5 wt.%) were prepared and the effect of these nanoclays on the epoxy resin flow characteristics was studied. It was found that the flow rate of resin continuously decreased as nanoclay content continuously increased. The reduction in the flow rate was attributed to the rate of change of curing and the subsequent change in viscosity of the nanoclay filled resin. Analysis of infusion process by Darcy’s law show that the permeability of the fiber decreased in the nanoclay filled resin system. Nanoclay filled laminates show improved static and dynamic mechanical properties than that of unfilled resin composites.     

新型树脂传递模塑技术

概述了传统树脂传递模塑(RTM)及在其基础上发展起来的新型RTM工艺,包括真空辅助树脂传递模塑(VARTM)、Seemann复合材料树脂浸渍模塑成型工艺(SCRIMP)和树脂膜渗透成型工艺(RFI)的成型原理、优点,并指出目前存在的缺点及解决方法.