三维织物厚度方向渗透率研究

复合材料的液体成型特点是树脂需在复杂结构纤维预制体中流经较长的距离,故探讨树脂在纤维织物中的流动行为尤为重要。研究了三维织物厚度、纤维细度以及纤维体积分数对类树脂液体在厚度方向渗透行为的影响,并分析了相关的流动行为规律。研究结果表明:当织物厚度较小时,树脂的渗透率随织物厚度增加而迅速下降;当织物厚度达到阈值时,渗透率因织物中孔隙减少而趋于定值。当织物的纱线细度降低时,纤维束间孔隙增大,使纤维束形状和结构发生改变,故渗透率增大;当织物厚度方向的压缩量增加时,纤维束间孔隙减少,孔隙形状趋于扁平,流动通道减少,故渗透率降低。     

纤维增强材料渗透性能的测量研究

渗透性是纤维预成型坯的特征常数，其值越大，说明树脂流过纤维集合体的阻力就越小，它是充模流动研究的主要内容。本文以平流法为基础，从理经和实验上对RTM充模中的面内渗透率张量作了研究。用三种有代表性的纤维材料即随机纤维毡、多层机织物和整体纺织物进行实验，所测各渗透率与计算结果吻合较好。并对影响渗透率的因素作了分析。     

非织造工艺对天然纤维增强体树脂流动性能的影响

纤维增强体的树脂流动性能是影响树脂传递模塑工艺设计及其复合材料质量的一个重要因素。本文利用单向法测试真空辅助传递模塑工艺中非织造工艺对亚麻纤维增强体对树脂流动性能的影响。结果表明,相同压力条件下,由平行铺网工艺制作的纤维增强体比交叉铺网工艺增强体树脂渗透率低,流动各项异性大;随着层数的增加及压力的增大,两种铺网工艺增强体的树脂渗透率降低,压力的变化对流动各向异性影响不大。     

一种快速比较纤维/树脂渗透率的方法研究

本文使用一种简单易行的方法对采用真空灌注成型时纤维/树脂间的渗透率进行了测量,在外界条件一定的情况下,通过本方法能够对真空辅助工艺中不同的纤维增强材料的渗透率进行量化对比。实验结果表明,利用本方法能简单快速地判断多种树脂/纤维组合的渗透率的相对差值,这对于采用真空辅助成型制备大型复合材料制品时的选材具有一定的指导作用。     

树脂传递模塑工艺中工艺参数对树脂-纤维界面的影响

本文系统研究了工艺参数对由树脂传递模塑成型的复合材料的拉伸强度和树脂-纤维界面的影响.这些参数包括注射压力和模腔/纤维毡的温度.在较低的注射压力和较高的成型温度下,纤维得到良好的浸润和粘结,成型复合材料的拉伸强度也较高.     

玻璃纤维的渗透率及其对RTM注模时间的影响

纤维的渗透率是ＲＴＭ成型工艺的一个重要参数，它对树脂在模腔中的流动状态重要影响。本文了玻璃纤维的渗透率及其影响因素，并导出了渗透率与注模时间的定量关系式。     

RFI工艺中有关树脂流动监测的研究

渗透率测量是树脂膜熔渗（阴）技术在复合材料设计和优化中最关键的条件。基于光导纤维视觉技术，通过纤维视觉传感器测量渗透率，能够在光强度下降的情况下探测出树脂的流动情况，这将易于我们在实际生产中在第一时间内准确的监测树脂的流动。     

纳米纤维增韧碳纤维树脂基复合材料的制备方法

一种纳米纤维增韧碳纤维树脂基复合材料的制备方法,属于复合材料领域。其特征为采用热塑性工程塑料的纳米纤维毡或膜作为增韧部分。其制备方法是:将碳纤维的预成型体作为静电纺丝的负极接收器,直接将热塑性工程塑料纳米纤维毡或膜纺丝于预成型体上,所纺纳米纤维毡或膜相对于碳纤维预成型体的树脂基体具有质量比例;将含有纳米纤维毡或膜的碳纤维的预成型体铺层,制备含纳米纤维夹芯结构的碳纤维预成型     

真空辅助成型工艺中亚麻纤维增强体树脂流动性能的研究

天然纤维复合材料是材料发展的重要方向,表面处理已成为天然纤维复合材料制备中的重要环节。本文研究真空辅助成型工艺(VARTM)中亚麻纤维增强体结构及表面处理对树脂流动性能的影响。结果表明,增强体相同方向的试样,沿试样相反方向测试的渗透率值不同;渗透率随真空压力及增强体层数的增大而减小;随着回潮率的增大,树脂流动性能降低,流动各向异性增大;氢氧化钠处理可提高树脂流动性能,但对树脂流动各向异性影响不大。     

熔融浸渍工艺参数对纤维束渗透率影响的研究

在连续长纤维增强热塑性复合材料浸渍模型中,渗透率是一个十分重要的参数。准确测量熔融浸渍工艺中高黏度树脂熔体浸润纤维束的渗透率,有助于浸渍模型更好指导熔融浸渍模具设计和工艺参数优化,制备出性能优异的热塑性树脂基复合材料。本文通过自制实验装置,测定了熔融浸渍工艺中高黏度树脂浸渍单向纤维束时纤维束张力和浸渍压力变化对渗透率的影响,根据实验结果拟合出工艺参数与渗透率关系的计算公式。结果表明：纤维束张力越大渗透率越低;浸渍压力越大,纤维束渗透率越大,但增大幅度随张力增大而降低。     

Resin flow monitoring inside composite laminate during resin film infusion process

In this article, a novel method of measuring resin flow front under vacuum condition is presented. The in situ monitoring system with metal hollow probe based on gas flow balance can be used in resin film infusion (RFI) process, where resin film is used and transverse flow is dominated along thickness direction of fiber preform. The diameter of the probe was chosen to increase the measuring accuracy, and the reliability of the method was evaluated by comparison of visualization experiment. Experimental results demonstrate that the method is suitable for monitoring resin flow in RFI process with and without autoclave, and can obtain the information about resin filling time, nonuniform flow front, and the permeability of fiber preform. Furthermore, by means of the established monitoring system, the influences of pressure and lay‐up sequence of carbon fiber fabric on epoxy resin flow during RFI process were investigated. In addition, resin flow pattern with changing viscosity of epoxy resin was studied. POLYM. COMPOS., 35:681–690, 2014. © 2013 Society of Plastics Engineers     

格构增强型复合材料夹层结构的制备与受力性能

真空导入成型工艺是一种新型的适合大型/异型复合材料结构件成型的技术.选用H-60 PVC泡沫、四轴向玻璃纤维布以及乙烯基酯树脂,通过在泡沫芯材上、下表面开槽,同时沿芯材厚度方向剖开,采用真空导入成型工艺制备出在结构上具有创新构型的格构增强型复合材料夹层结构.研究结果表明,真空导入成型工艺充模速度快、成型效益高;格构增强型复合材料夹层结构的剪切、平压与抗弯性能均较传统夹层结构得以提高;其格构腹板可有效抑制泡沫芯材剪切裂纹的扩展,避免面板与芯材的剥离破坏;阐明了格构增强型复合材料夹层结构的受弯极限承载能力.     

高熔体指数PP专用料研制

简要介绍了以分子量较高的聚丙烯为基础树脂,采用化学降解一步法制得纤维级聚丙烯树脂的过程。该树脂等规指数高、分子量分布窄、熔体指数在20～80g/10min内可调,是高、中速纺丝及熔喷法、纺粘法无纺布的理想原料。     

Online monitoring and analysis of resin pressure inside composite laminate during zero‐bleeding autoclave process

Resin pressure is one of the most important parameters in manufacturing composites during autoclave process. It not only greatly influences resin flow behavior, but also has effects on void formation and elimination. Online monitoring resin pressure can provide an important guidance for the optimization of the processing parameters and the control of the quality of composites. In this study, a resin pressure online measuring system for autoclave process was established based on the principle of pressure transfer in liquid, and the size of the measuring probe of the system was optimized to increase the accuracy of measured resin pressure. The results indicate that the accuracy and the dynamic response of the system can meet the requirements of resin pressure measurement during autoclave process. Furthermore, by means of this proposed resin pressure measuring system and the measurements of compaction properties of the fabric stacks, the resin pressures inside carbon fiber fabric/epoxy resin and glass fiber fabric/epoxy resin prepreg stacks during autoclave process were investigated, especially for the zero‐bleeding process which is prevailing for aircraft composite structures. It is demonstrated that during zero‐bleeding process, the resin pressures, which conform to the spring and piston model, uniformly distribute along through‐thickness and in‐plane directions. In addition, the resin pressure profile is significantly influenced by the fiber volume fraction of the prepregs, indicating that fiber content of prepreg should be optimized for achieving free defects and uniform fiber distribution. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Permeability model for a woven fabric

The resin transfer molding (RTM) method is used to manufacture composite parts. The reinforcing fibers are placed in a mold cavity and the resin is injected to fill up the empty spaces. After the resin cures, the mold is opened and the part ejected. To predict necessary pressures and filling times and the proper locations for the inlet ports for resin injection and vents for air ejection it is necessary to model the resin infiltration process. A key to this modeling is permeability which characterizes the resistance of fibers to the flow of infiltrating resin. A simplified model for in-plane permeability of fabric reinforcement (preform) is developed here. This model uses lubrication theory for modeling the flow through open pores and Darcy's law for the transverse flow through the reinforcement. Scaling analysis is provided to justify the simplification and to estimate the range of validity for resulting expressions. Extension of the model to cover multi-layered preforms is derived. Boundary conditions and the data necessary to specify the problem geometry are discussed. A numerical experiment is conducted to estimate the influence of the transverse permeability of the preform on the solution. A calculation is provided for the permeability of a plain weave fabric.     

RTM制造技术的新进展

本文介绍ＲＴＭ制造技术在扩大树脂的应用品种、制造高纤维体积含量、多维织物及预成型坯件制件、柔性膜ＦＲＴＭ技术和树脂压注及固化过程监控等方面的新进展。     

Flow enhancement in liquid composite molding processes by online microwave resin preheating

Liquid composite molding techniques are increasingly applied for the manufacturing of fiber-reinforced plastic components for civil, aerospace, and automotive applications. Being the preform impregnation a key step during the process, resin viscosity should meet the precise requirements. Opportune resin preheating increases its fluency, thus enhancing the impregnation and saturation flow through the fabric and reducing the mold filling time. This paper explores the application of microwave technology for resin preheating. The integration of an online microwave preheating system within a demonstrative resin infusion facility is described and the effects of preheating on the infusion time are discussed. Parallel-plate dielectric sensors were embedded into the mold to track the unheated and preheated resin flow through the fiber preform. The obtained results highlighted the effectiveness of online microwave heating to reduce the time required for the impregnation of the dry fiber reinforcement.     

Anisotropic in-plane permeability of fabric media

An elegant procedure is proposed for obtaining components of the orthotropic or anisotropic in-plane permeability tensor from experimental data on flow front position and time. A radial flow geometry allows the shape of the advancing flow front to be dictated by the in-plane permeability of the fabric media. The directional permeabilities in the fabric plane are directly calculated from fluid and fabric properties together with data from the mold filling experiment (resin injection pressure and flow front position with time). The simplicity of the apparatus and proposed analytical procedure permit easy testing and comparison of different types of fibrous media.     

Development of an isothermal lubricating layer model for injection pultrusion of electronic prepregs

The current process for manufacturing electronic prepregs uses solvent‐based resin systems. Solvents are environmentally unfriendly and contribute to voids in the pre‐preg, which are a source of product variability. Prepreg inconsistencies are one of the major sources of scrap on the board shops. To overcome these drawbacks, a solvent‐less process is currently being developed in our laboratory. The process is based on the concept of injection pultrusion or continuous resin transfer molding (RTM). The centerpiece of the process is an impregnation die. Glass fabric and resin are fed into the die where fiber impregnation and partial resin cure occurs depending on the material chemo‐rheology. The B‐staging is finished in an oven located immediately after the die. A key to the success of the process is being able to predict the pulling force. Fabrics used in electronic prepreg manufacturing are relatively fragile; they could be damaged if the pulling force is too high. A model to predict the pulling force, based on the formation of a continuous lubricating layer between the die surface and the moving fabric, has been developed and experimentally tested using model fluids.     

泡沫夹层结构VARI工艺中树脂流动行为的研究

采用可视化实验方法研究了泡沫夹层结构真空辅助成型工艺(VARI)中树脂的流动行为.结果表明,导流介质的存在可以明显提高树脂的流动速率;剥离布可使得复合材料泡沫样板表面光滑平整,并可明显提高充模速率,减少充模时间;增加浇注口数目可明显缩短充模时间,并可获得浸渍均匀、沟槽全满的样板.采用真空点源布局B时的树脂流动速率大于真...