树脂膜熔渗(RFI)工艺及其发展现状

概述了一种新型的复合材料成型技术——树脂膜熔渗(RFI)工艺的国内外发展现状、成型原理、工艺特点及对材料的设备要求,描述了该工艺过程中的树脂流动模型、热传递模型、粘度模型、固化模型以及预制体的压实模型与复合材料的成型及材料力学性能的关系。作为一种新型低成本的复合材料成型工艺,其成型的复合材料性能高、成本低且环境污染小,目前主要应用于国防领域中,随着该成型工艺的进一步发展,在民用领域中也将发挥巨大的作用。     

Effect of compression process on void behavior in structural resin transfer molding

To realize low void content molded parts, we propose structural resin transfer molding (SRTM) with the compression process. Resin was injected with a gap height between the upper and lower halves of matched metal dies. Mold filling was performed by a squeezing motion of the upper mold die. The usefulness of the compression process was examined by comparison to a conventional SRTM method. Void distribution and bending properties in both processes were compared. The SRTM method with compression was better at driving out voids. The effects of the gap height between the upper and the lower halves of the molds and of the gap closure rate during mold closing after injection on the void distribution were examined. The gap height did not affect the void distribution. When the gap closure rate was high, the voids were expelled towards the end of cavity, whereas voids remained on the top surface of the molded parts using a small gap closure rate. The difference in void behavior due to the gap closure rate was determined by a balance of the permeability between the flow and the transverse directions.     

RFI成型工艺中渗透率的研究及树脂流变模型的建立

渗透率测量是树脂膜熔渗(RFI)工艺在复合材料设计和优化中最关键的条件。随着纤维体积分数的增加,渗透率非线性降低,可见纤维体积分数的变化对整个树脂体系浸渍纤维预制体有很大的影响。在黏度实验的基础上,对用于RFI工艺的环氧树脂体系的化学流变特性进行研究,并根据双阿累尼乌斯方程建立树脂体系的流变模型,为合理地制定RFI工艺参数、保证产品质量和实现工艺参数的全局优化提供科学依据。     

一维RFI工艺流动模型的建立及数值模拟

在已知叠层结构预制件渗透率的基础上,根据树脂的流动特点,建立一维树脂膜熔渗(RFI)工艺的流动模型,通过数值模拟推导在不同纤维含量预制件中,树脂湿润高度、树脂湿润区域内树脂流动速度和压力分布规律,为设计制件结构尺寸,优化真空袋固化成型工艺参数提供了理论依据。     

Effect of gravure process variables on void area in shrink film

The gravure print quality on shrink film depends on process parameters and is fairly gaged by minimum print defects such as voids. The visibility of these defects is visually disturbing and could result in product rejection. This article investigates the effect of process parameters such as viscosity, speed, hardness, and line screen frequency on ink transfer from recess gravure cells and hence on print voids in an attempt to minimize them. A general full factorial design with the abovementioned four independent variables was analyzed by variance, main, and interaction effects. The results revealed line screen, hardness, and ink viscosity as the most influential factors in minimizing the defect. A regression model was developed to predict void area. The model was validated by conducting an additional 11 runs on the press. The predicted values from the model were in close agreement with the press results. The results showed a commendable decrease in the void area by 65%.     

A structure and property based process window for void free thermoset composites

A process window providing guidelines to minimize internal stress levels and to prevent void formation during cure of thermoset composite materials is presented. A model taking into account the applied pressure and the level of stress borne by the fiber assembly was introduced to calculate the hydrostatic internal stress state in the resin during cure. Based on the fundamental mechanisms of matrix shrinkage and evolution of viscoelastic properties under the given processing conditions, the internal stress in the resin was calculated as a function of fiber volume fraction, fiber stacking sequence, applied pressure and resin conversion. This level of stress is compared to a criterion for void initiation in the resin. A process window was hence constructed for preventing void formation during cure. Composite laminates with different stacking sequences and fiber volume fractions were cured with different applied pressures within and out of the process window boundaries. The composite void contents were measured and correlated perfectly with the process boundaries. This process window construction taking into account the material vis‐coelastic properties and the composite architecture is a unique tool for determining optimum process condition of composite laminates.     

苯并咪唑螯合树脂的性能与结构表征

研究以环氧聚合物为基质的苯并咪唑螯合树脂的结构性能以及配位机制.已合成含有BBPAH的新型螯合树脂,测定其在pH 0～6.0的缓冲溶液中对Cu2、Ni2+、Zn2+、Cd2+和Co2+的配位容量.实验结果表明,在pH0～2.0条件下对Cu2+、Zn2+、Cb2+的配位容量分别为0.84、1.65、0.84 mmol/g,显示出很高的配位选择性.对络合Cu2+树脂进行了EPR表征和配位场的研究,初步证明为四面体配位结构.同时对苯并咪唑螯合树脂在强酸条件下吸附金属离子的机制进行了探讨.     

A novel condensation-addition-type phenolic resin (MPN): Synthesis, characterization and evaluation as matrix of composites

This paper reports a novel methylol and propargyl-containing dual-cure-mechanism novolac-based phenolic resin (MPN). MPN resins with varying contents of reactive groups were synthesized by a two-step one-pot method facilly and characterized by Flourier transfer infrared spectra (FT-IR), hydrogen magnetic resonance spectra (¹H NMR), gel permeation chromatography (GPC), dynamic scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. The resins could be thermally cured by two gradual but fused stages: Condensation of methylol groups and addition polymerization of propargyl groups. This novel resin has advantages over conventional condensation-cure and addition-cure phenolic resins in processing capability. The results of DMA and thermogravimetry analysis (TGA) showed the cured resins possessed high thermal properties. Evaluation of MPN as matrices for advanced composites indicated the enhanced crosslink network derived from dense reactive groups in one single molecule was beneficial to the admirable thermal stability, but was detrimental to the mechanical properties of the resultant composites. MPN resin was amongst ideal candidates for matrices of high temperature materials.     

树脂乳胶成膜过程的研究现状与前景

介绍了成膜扩散的主要理论模型及影响因素。树脂乳胶膜的性能不仅与涂料的配方和其中聚合物的分子链结构有关,而且与聚合物的成膜过程密切相关。聚合物成膜时的扩散在许多应用中是非常重要的。先进技术在成膜表征中的应用使得本领域的研究人员对于扩散过程有了广泛而深入的认识。     

纳米羟基磷灰石/天然胶乳复合乳胶膜的制备及性能表征

对比研究了纳米羟基磷灰石(n-HA)经硅烷偶联剂(KH-570)表面改性前后的性能变化,实验结果表明,n-HA经改性后,疏水性得到提高,其表面与KH-570发生了偶联作用(FT-IR);将改性的n-HA与天然胶乳复合制备复合乳胶膜,力学性能测定结果表明,复合乳胶膜的力学强度与未经处理的相比有一定提高;另外n-HA还能够有效的抑制复合乳胶膜中水溶性蛋白的析出,利用考马斯亮蓝法测定复合材料中的水溶性蛋白,随着n-HA的添加量的增加,复合乳胶膜中的水溶性蛋白被屏蔽,溶出量逐渐降低。     

树脂基复合材料界面结合的研究Ⅰ:界面分析及界面剪切强度的研究方法

本文分析了树脂基复合材料受力状况下对界面结合的要求,着重介绍了微量冲击和临界纤维断裂长度分析两种检测树脂基复合材料界面剪切强度的方法及其研究成果.通过对单丝纤维断点周围基体树脂形态的分析,提出了一种判断优化界面的方法.     

4,4′-(双3,4-二氰基苯氧基)联苯树脂复合材料研究

以二苯砜二胺为固化剂,钼酸铵为催化剂合成了4,4′-(双3,4-二氰基苯氧基)联苯(BPH)的预聚物树脂,采用溶液浸渍法制备了玻璃纤维布预浸料,热压方式制备了玻纤增强4,4′-(双3,4-二氰基苯氧基)联苯树脂复合材料。通过示差扫描量热仪(DSC)、旋转流变仪(Rheometer)、傅里叶变换红外光谱(FTIR)、热重分析仪(TGA)和扫描电子显微镜(SEM)对树脂的固化反应,化学结构,复合材料的热稳定性和断面形貌进行了研究与表征。结果表明,钼酸铵可以显著的促进单体的预聚反应,聚合物玻璃化转变温度为380℃,复合材料具有优良的热稳定性,在氮气和空气中的5%分解温度分别为542℃和482℃,375℃处理20 h后弯曲强度保持率为97%,沸水中处理24 h后吸水率为1.4%。     

Nanoscale characterization of engineered cementitious composites (ECC)

Engineered cementitious composites (ECC) are ultra-ductile fiber-reinforced cementitious composites. The nanoscale chemical and mechanical properties of three ECC formulae (one standard formula, and two containing nanomaterial additives) were studied using nanoindentation, electron microscopy, and energy dispersive spectroscopy. Nanoindentation results highlight the difference in modulus between bulk matrix (~ 30 GPa) and matrix/fiber interfacial transition zones as well as between matrix and unreacted fly ash (~ 20 GPa). The addition of carbon black or carbon nanotubes produced little variation in moduli when compared to standard M45-ECC. The indents were observed by electron microscopy; no trace of the carbon black particles could be found, but nanotubes, including nanotubes bridging cracks, were easily located in ultrafine cracks near PVA fibers. Elemental analysis failed to show a correlation between modulus and chemical composition, implying that factors such as porosity have more of an effect on mechanical properties than elemental composition.     

Behavior of carbon matrix in carbon fiber reinforced composites (CFRC) synthesized through the film boiling chemical vapor infiltration (FB-CVI) process

Film boiling chemical vapor infiltration (FB-CVI) technique is considered as one of the fastest process to manufacture carbon fiber reinforced carbon (CFRC) composite products. In the present work, the characteristics of the carbon matrix deposited through FB-CVI process under deposition and infiltration are investigated. A novel reactor with unique features was developed, to simulate the process conditions. Utilizing the indigenously build reactor, pyrocarbon (PyC) was deposited on graphite substrates. The kinetics of the process is investigated within temperature range of 1100 °C–1150 °C and characteristics of carbon matrix was investigated. The nature of the carbon deposited and effect of graphitization on the microstructure of the deposited PyC was examined. The role of preform architecture on densification through FB-CVI process and characteristics of the composites were further studied. The mechanical behavior of the FB-CVI based CFRC material were investigated through nanoindentation technique. The present study has provided process guidelines for densification of 2D continuous fibers based preform. Structure property relationship is evolved to optimally develop CFRC composite products for aerospace applications.     

Graphite/Polyaniline (GP) composites: Synthesis and characterization

Ever since the discovery of inherently conducting polymers (ICPs), research dealing with the applications of these unique materials continues to grow. The use of ICPs, especially polyaniline (PANi) and polypyrrole (PPy), and carbon black (CB) as conductive additives in the thermoplastics industry have been limited due to undesirable properties of each at high temperatures. Carbon black-ICP composites, however, have shown improved properties at higher temperatures. The applications of these composites are still limited because the conductivities are below that of carbon black alone and about the same order of magnitude as PANi. Graphite/ICP composites have also been touted as possible electrode materials in rechargeable batteries and have numerous other applications. The exploration of graphite/PANi composites in our research lab has yielded conducting composites which exhibit conductivities greater than the graphite or PANi alone. In addition to higher conductivities, these graphite/PANi composites exhibit controllable conductivities as a function of pH.     

Processability and properties of phenoxy resin toughened phenolic resin composites

A novel method has been developed to toughen phenolic resin using phenoxy resin. Phenoxy resin was dissolved in phenol to form a glutinous mixture at 110°C, and an acid catalyst (p-toluene sulfonic acid, PTSA) was utilized to reduce the viscosity of mixture. The mixture was blended with resole-type phenolic resin. IR spectra confirmed that the amount and strength of hydrogen bonds increased with PTSA content, and the viscosity decreased with PTSA content in the polymer blends. The wet-out of glass fiber by modified resin was improved. The flexural and notched Izod impact strength of the polymer-blend composites increased significantly. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 911–917, 1997     

Microstructure and dielectric response of (Ba,Sr)TiO3 filler-dispersed resin composites

Resin-matrix composites dispersing low-loss dielectric ceramic filler have received a considerable interest for high-frequency application, because of their good shape flexibility and controllable dielectric properties. In this study, (Ba,Sr)TiO₃-type ceramic particles have been synthesized by KCl molten salt method to serve as filler particle for resin-matrix dielectric composite. Dielectric measurement confirmed that the composite fabricated by tape-casting demonstrated two times higher dielectric constant of 50.4 than the other composites fabricated by direct-casting using a metal mold. Pore-size distribution as well as ceramic filler content was strongly correlated with the formation of electrical flux in the composites to enhance dielectric constant.     

超支化聚合物接枝纳米TiO_2/环氧树脂复合材料的制备与表征

利用偶联剂KH-550和超支化聚(胺-酯)(HBP)对纳米TiO2进行改性,并制备了纳米TiO2/环氧树脂(EP)复合材料。对复合材料的结构、力学性能、加工性能以及热性能进行了研究。研究结果表明,HBP接枝改性纳米TiO2(TiO2-g-HBP)的引入可明显提高复合材料的力学性能、热性能及加工性能;当w(TiO2-g-HBP)=1%时,复合材料的力学性能最好,其冲击强度和弯曲强度比纯EP分别提高了135.51%和22.98%;扫描电镜(SEM)结果显示,TiO2-g-HBP/EP复合材料由脆性断裂转变为韧性断裂。     

Two-dimensional Raman spectroscopic study on the structural changes of a poly(3-chlorothiophene) film during the heating process

Two-dimensional Raman spectroscopy has been applied to provide the information on charge carriers and thermal stability of a doped poly(3-chlorothiophene) (PCTh) film. The strong spectral intensity at 1420 cm⁻¹ shows that positive polarons are the major charge carriers in doped PCTh. On the other hand, peaks in the 2D contour maps separate the overlapped bands around 1386 cm⁻¹, confirming the existence of positive bipolarons in PCTh. The positive asynchronous cross peak located at 1420/1386 cm⁻¹ further indicates that bipolarons have a higher thermal stability compared with polarons in the doped PCTh. The increase of the spectral intensity at 1454 cm⁻¹ and the decrease of the spectral intensity at 1420 cm⁻¹ indicate that during the heating process, a structural change occurs in the PCTh film.