软模/真空灌注成型内翻法兰半球的工艺探讨

为解决复杂复合材料构件的整体一次成型问题,提高复合材料制品的整体性能,降低生产成本,本文采用硅橡胶制备软模,利用其柔韧性解决常规模具无法一次成型的问题。并通过软模/真空灌注工艺制备了带内翻法兰半球,以验证其工艺可行性。通过比较与其他工艺制备的复合材料的性能,探讨其使用前景。结果表明:采用软模/真空灌注工艺可一次整体成型内翻法兰半球等复杂构件,制品的性能稳定。     

软模/真空辅助RTM工艺用模具设计与制备

以一个典型构件缩比件为例,介绍了软模及真空辅助RTM工艺用模具的设计和制备过程.实践证明,这种工艺可应用于复杂结构复合材料构件成型技术领域.     

软模辅助RTM制备舱段缩比件

本文以某型号舱段研制为背景,提出用软模辅助RTM整体成型复杂结构的复合材料构件,依据舱段结构特点,设计了缩比件,并用聚氨酯软模和硅橡胶软模分别成型了碳纤维/环氧复合材料缩比件。研究结果表明,硅橡胶软模和聚氨酯软模都可以成型出外形完整、尺寸准确的缩比件,硅橡胶软模的挤胶效果明显好于聚氨酯软模,但是总体上软模挤胶效果不是很明显,本文对此进行了分析讨论。实验表明,软模辅助RTM可以整体成型内部结构复杂的复合材料构件,本文还对今后的研究提出了设想。     

复杂多筋复合材料壳体的模具设计技术研究

针对复杂多筋壳体的结构特点,以及VARTM整体成型工艺特点,提出了一种新型的易碎模成型模具。在常规模具的基础上设计与制造了该易碎模,利用真空辅助灌注工艺成功制造了壳体的样机,满足了产品设计技术要求,为内部有交错筋的壳体结构复合材料产品的模具设计技术提供了一种新的思路。     

用于RTM工艺的软模材料的工艺性能

本文对COCA31-11有机硅橡胶模具的硅橡胶的粘温特性、试件基本力学性能及软模试用效果等工艺性能进行了研究;研究结果表明,硅橡胶的浇铸温度在25℃~30℃之间可以满足浇铸成型工艺窗口要求,当硅橡胶硫化工艺为:30℃硫化24 h、90℃后硫化1 h时可以保证软模具有良好的力学性能;用浇铸成型的硅橡胶软模进行碳纤维复合材料构件的试制,软模和产品外形完整、尺寸准确,证明了COCA31-11硅橡胶可以作为软模辅助RTM工艺中软模材料使用。     

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。     

红外加热缠绕成型工艺参数对CF/PEEK复合材料层间剪切性能的影响

为获得层间粘结性能优异的连续碳纤维增强聚醚醚酮复合材料(CF/PEEK)缠绕成型制品,以粉末浸渍法制备的CF/PEEK单向带为原料,采用自制的高功率红外加热热塑性复合材料缠绕成型设备,进行缠绕成型工艺的研究。以层间剪切强度(ILSS)作为评价缠绕制品性能的主要依据,分别研究了缠绕成型过程中的送料张力、下压辊压力、缠绕速率、加热温度、预热时间和冷却速率等关键工艺参数对CF/PEEK环制品性能的影响。实验结果表明,成型温度为410℃,预热为40 min,送料张力为8 kg,下压辊气缸压力为0.30 MPa,芯模转速为6 r/min,缓慢冷却条件下制得的缠绕制品性能最优,层间剪切强度达到(82.29±1.27) MPa,并据此制备出了CF/PEEK缠绕管道。     

碳纤维增强环氧树脂复合材料的液体成型及其性能研究

本文研究了不同温度下RIM145树脂的粘度和适用期,分析了不同温度下RIM145树脂和碳纤维单丝之间的浸润性;并以碳纤维单向布为增强材料,采用真空辅助灌注成型工艺制备了碳纤维增强环氧树脂(CF/EP)复合材料,研究了复合材料的力学性能,对层间剪切试样剖断面形貌进行了SEM分析,并研究了使用VAP单向透气膜辅助真空灌注成型工艺对CF/EP复合材料厚制件灌注质量的影响。研究结果表明,RIM145树脂基体在50~70℃粘度低、适用期长且树脂与碳纤维单丝之间的浸润性良好,适用于CF/EP复合材料的真空辅助灌注成型工艺;灌注的CF/EP具有良好的力学性能,树脂和纤维具有中等粘结强度界面,采用VAP单向透气膜辅助真空辅助灌注成型工艺可降低CF/EP复合材料的孔隙率。     

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.     

复合材料液体模塑成型技术

复合材料液体模塑成型技术(简称LCM)是指将液态聚合物注入铺有纤维预成型体的闭合模腔中，或加热熔化，预先放入模腔内的树脂膜，液态聚合物在流动充模的同时完成树脂／纤维的浸润并经固化成型为制品的一类制备技术。树脂传递模塑、真空辅助树脂传递模塑、树脂浸渍模塑成型工艺、树脂膜渗透成型工艺和结构反应注射模塑成型是最常见的先进LCM工艺技术。这类工艺的共同特点是将纤维预成型体放入模腔内，     

Numerical simulation of resin infusion and reinforcement consolidation under flexible cover

This paper presents the physical phenomena and equations governing resin infusion under a flexible cover. This composite manufacturing process known as vacuum assisted resin infusion (VARI) is analyzed here when the reinforcement is covered by a thin plastic film and resin is injected by gravity after a partial level of vacuum has been achieved in the cavity. In this process, the plastic cover is deformed as the resin fills up the mold cavity. Coupling between the mechanical deformation of the flexible cover and the resin flow inside the mold cavity is described by a set of mathematical equations with boundary conditions. Based on this model, a general methodology is developed to simulate numerically the resin flow during the infusion process. Validation of the numerical results is performed by comparison with a series of experiments. POLYM. COMPOS. 26:417–427, 2005. © 2005 Society of Plastics Engineers     

Electromagnetic Field-Aided Magnetic Soft Mold Reverse Imprinting Technology Applied in Microstructure Replication

This paper proposes an advanced microstructure embossing replication technology that combines an electromagnetic-field-aided magnetic soft mold and a reverse imprinting technology to replicate microstructure. The main advantage of this technology is low pressure, low cost, and quick and easy forming. The entire imprinting process can be completed at room temperature using a ultraviolet (UV) curing technique. This study applied a compound casting technique to fabricate a magnetic poly(dimethylsiloxane) (PDMS) soft mold, with an electromagnetic chuck for even imprinting pressure, and reverse imprinting molding technology. Microstructure cavity of the mold was fully filled with photoresist before imprint replication, and improved microstructure transfer ratio. Examination of the results showed that, the magnetic PDMS soft mold integrated electromagnetic-field-aided reverse imprinting process developed by this study, can successfully replicate microstructure at room temperature, low pressure, and avoid deformation and residual stress problems due to heating and cooling.     

Effects of the addition of a cover mold on resin flow and the quality of the finished product in vacuum‐assisted resin transfer molding

For vacuum‐assisted resin transfer molding (VARTM), we propose adding a cover mold, inserted between the distribution medium and the peel ply, to achieve a higher fiber volume fraction in the final product. As the conventional VARTM process does not use a cover mold, improved processes using different rigid covers were explored. A three‐dimensional digital image correlation system was developed to monitor the thickness evolution of the vacuum package during the infusion stage. This system was validated as a full‐field displacement test. The results demonstrate that there are three advantages to using a cover mold. First, in the filling stage, a rigid cover mold can prevent shrinkage of the part at the resin flow front, and even cause slight expansion of the unsaturated part. This improves the resin flow and shortens the time required for complete infusion. Second, a cover mold can limit the amount of excess resin needed to infuse the saturated part. Third, in the postfilling stage, the cover mold can be used to accelerate extrusion of the excess resin in the package. The overall effect is to increase the fiber volume fraction in the final product. POLYM. COMPOS., 37:1435–1442, 2016. © 2014 Society of Plastics Engineers     

Modeling and analysis of thickness gradient and variations in vacuum‐assisted resin transfer molding process

As vacuum‐assisted resin transfer molding (VARTM) is being increasingly used in aerospace applications, the thickness gradient and variation issues are gaining more attention. Typically, thickness gradient and variations result from the infusion pressure gradient during the process and material variations. Pressure gradient is the driving force for resin flow and the main source of thickness variation. After infusion, an amount of pressure gradient is frozen into the preform, which primarily contributes to the thickness variation. This study investigates the mechanism of the thickness variation dynamic change during the infusion and relaxing/curing processes. A numerical model was developed to track the thickness change of the bagging film free surface. A time‐dependent permeability model as a function of compaction pressure was incorporated into an existing resin transfer molding (RTM) code for obtaining the initial conditions for relaxing/curing process. Control volume (CV) and volume of fluid (VOF) methods were combined to solve the free surface problem. Experiments were conducted to verify the simulation results. The proposed model was illustrated with a relatively complex part. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Key factors affecting permeability measurement in the vacuum infusion molding process

The composites industry, under increased environmental constraints, is seeking to shift from existing open mold manufacturing processes for composite parts. A promising manufacturing technology known as the vacuum infusion molding process is gaining acceptance among composite-parts manufacturers since it involves low tooling cost and allows complete elimination of volatile organic compounds (VOC). The process is similar to the resin transfer molding process; however, in the vacuum infusion technique, a polymeric film, often referred to as vacuum bag, replaces the stiff mold cover. The film is sealed against the lower half of the mold, at the periphery. Air expelled from the mold cavity results in the compaction of the reinforcement by the atmospheric pressure present on the outer side of the polymeric film. Finally, resin impregnates the mold cavity, usually through a resin distribution channel. The process is mainly developed for large-scale structures, where material cost is an important parameter and users cannot afford any production pitfalls. Among process parameters that affect resin flow in the vacuum infusion molding process is the permeability of the reinforcement stack, which has to be measured and evaluated taking into consideration the requirements of the process. A possible approach is the definition of a parameter that defines the maximum infused length, and this parameter will take into account the structure of the reinforcement, the resin viscosity, the fiber volume fraction and inlet geometry.     

湿膜压纹工艺技术的应用

湿膜压纹工艺是指载有无溶剂粘稠状的树脂涂料的基材在包覆成型模具时,涂料与模具的微细图案面接触,复制模具图案,同时施以光固化、电子辐射等固化手段,使涂层瞬间固化,并保持模具微细图案的形状,逐渐从模具上剥离,制得表面附有特殊图案的涂层产品的工艺过程。湿膜压纹工艺在显示器用功能薄膜、电子产品装饰膜(IML)、皮革离型纸、LED照明用增光板等产品的生产中起着重要作用。当今显示行业、IML行业市场、人造皮革花型复型性要求提高、低能耗LED照明产品逐步普及,湿膜压纹工艺的应用领域也日益扩大。本文将着重介绍湿膜压纹工艺中软模与硬模的工艺特点、关键技术以及其应用于增亮膜(棱镜膜)、微棱镜膜、防眩膜生产的最新进展。     

A Study of an Innovative Technology for Manufacturing Optical Waveguides Based on Vacuum-Assisted Micromolding

In this study, we develop a vacuum-assisted photo resist filling technology for micro-structures by integrating the characteristics of PDMS soft mold, photo cure resist, and vacuum equipment. Together with soft mold, this technology can be adopted in the production of optical waveguide components. Conformal contact can be achieved on the material surface with PDMS soft mold. Meanwhile, it has a low surface free energy and won't stick to the resist during the filling. By vacuum pumping, the resist filling will be compact and complete. It increases the effective filling area significantly.     

塑料机器人一模多异腔注射模设计

以塑料机器人产品为载体,介绍异型组合产品的结构工艺性,确定该产品采用一模多异腔的成型方案。基于计算机辅助工程（CAE）数值模拟技术优化模具浇注系统的设计,解决流道填充不平衡的问题;同时在流道上增设特殊结构,解决注塑生产后产品的空间存放问题。根据产品的功能要求,在模具结构中设置抽芯机构,以解决产品成型后产生夹线的工艺问题。该模具在实际的生产过程中取得较好效果,为类似模具的设计提供相关的参考与借鉴。     

Rapid Vacuum Infusion and Curing of Epoxy Composites with a Rubber-Cushioned Mold Design

Vacuum resin infusion has been developed as a low-cost process for manufacturing fiber-reinforced composites with high fiber loading. However, it is an extremely slow process due to the long time required to prepare a vacuum-tight mold and further to cure the resin at room temperature. In this work, a new mold with a rubber cushion suitable for rapid infusion and rapid curing under complete negative pressure was designed and fabricated. Experimental results demonstrated that the new mold is suitable for rapid heating and withstand dynamic loading under complete vacuum force. Composite plaques can be produced with a short cycle time of several minutes while desired mechanical properties are still achieved. Thermal analysis and rheological measurements were performed to study epoxy curing at elevated temperatures and define an optimal process window for rapid vacuum infusion. This study leads to the development of a completely vacuum-based liquid molding process that uses simple tooling, yet is suitable for rapid production.