Part Thickness Variation during the Vacuum Assisted Resin Infusion Process

An experimental procedure was designed to monitor the preform thickness change real-time throughout the vacuum assisted resin infusion( VARI) process. Two kinds of liquid with different viscosity were infused with different post-filling time. The variation of the part thickness during the VARI process was studied. And the effect of the post-filling time on the part thickness was investigated.The results indicate that the compaction behavior of the preform can be divided into three stages,and the fiber volume fraction varies with the post-filling time in a similar sinusoid form. In addition,the post-filling should be overtime for the greatest fiber volume fraction,and when the resin is infused with higher viscosity,the greatest fiber volume fraction is higher.

Mold Filling Analysis in Vacuum Infusion Molding Process Based on a High-Permeable Medium

The objective of this paper is to understand the flow mechanism through visualization experiments and discuss theinfluence of process parameters on mold filling process. A 2D leakage flow model is developed to simulate the moldingprocess, and the simulation results show good agreement with experiments.

Vacuum Infusion Molding Process Part 1:VIMP Based on a High-Permeable Medium

The visualization experiments were carried out to investigate the permeability of the high permeable medium (HPM) and the roles of the peel ply and the HPM in the mold filling.The influence of process parameters on mold filling is discussed.Furthermore,the whole vacuum infusion molding process (VIMP) procedure is introduced in detail taking the manufacture of a model boat for example.

Vacuum Infusion Molding Process (Part 2 VIMP Based on Grooves)

The optimal parameters for flow grooves and supply grooves were determined by a series of experiments,and the influences of various molding conditions on the mold filling process were analyzed.Furthermore,the whole VIMP procedure based on grooves was introduced in detail taking the manufacture of a sandwich panel as an example.

Formulating Novel Halogen-Free Synergistic Flame Retardant Epoxy Resins for Vacuum Assisted Resin Infusion Composites

The most common process to manufacture advanced composites is the costly autoclave.One of the out-of-autoclave alternatives is the low-cost vacuum assisted resin infusion(VARI)which produces quality parts with less pollution.Epoxy resin is a widely used composite matrix resin,but its high flammability limits its use as interior composite parts for vehicles.The usual flame retardant for epoxy involves halogen,which is effective but has high smoke toxicity.As a result,halogen-free flame retardant epoxy resin systems become dominant.In this paper,phosphorus flame retardant was combined with benzoxazine(BOZ)to produce synergistic effect and achieve satisfactory flame retardance,as well as mechanical improvement for the epoxy resin.Differential scanning calorimetry(DSC),dynamic mechanical analysis(DMA),thermal gravitational analysis(TGA),the cone calorimeter(CC),and limiting oxygen index(LOI)were used to characterize the resins.The results showed significant improvement on the flame retardance of the synergistically modified resins.Specifically,the carbon residue increased by 113.6%,and the char thickness increased by 6 to 7 times,compared to those of the flammable benchmark resin.The LOI reached 33 and passed the UL94 V-0 vertical burn rating.The modified resins also exhibited adequate stability and viscosity suitable for VARI processes.

Rheological Behaviors and Processing Windows of Low Viscosity Epoxy Resin for VIMP

The chemorheological behaviors of a low viscosity epoxy resin system （Huntsman 1564/3486） for vacuum infusion moulding process （VIMP） were studied with viscosity experiments.The dual-Arrhenius rheological model and the engineering viscosity model were established and compared with the experimental data.The result showed that the viscosity in the earlier stage calculated by dual-Arrhenius model were smaller than the experimental data,while the data calculated by the engineering model were larger.Combining the two models together can predict the rheological behaviors of the resin system in a more credible manner.The processing windows of the resin system for VIMP were determined based on the two models.The optimum processing temperature is 30-45 ℃.

Investigation of carbon fiber composite stiffened skin with vacuum assisted resin infusion/prepreg co-curing process

Co-cured vacuum assisted resin infusion process(co-VARI process),which combined vacuum assisted resin infusion(VARI)with prepreg vacuum bag only process(VBO),was adopted to fabricate T-shaped stiffened skin with non-crimp fabric(NCF)stiffener and prepreg skin.During compaction stage of co-VARI process,prepreg resin impregnated fiber fabric under elevated temperature and vacuum pressure.This phenomenon was characterized by fluorescent micrographs with different holding temperature and time.Its influences on processing quality and mechanical performance for co-VARI stiffened skin with different filler materials at triangular region were further analyzed by optical micrographs and pull-off test,respectively.The results show that increasing holding temperature and prolonging holding time can promote prepreg resin impregnation in fiber fabric.Moderate prepreg resin impregnation is favorable to reduce resin rich region and increase fiber volume fraction at prepreg-fabric interface.Moreover,prepreg resin impregnation effect plays significant roles on pull-off performance for co-VARI stiffened skin with fabric filler but has negligible influences on specimens with prepreg filler.In addition,compared with stiffened skin with fabric filler,superior processing quality and pull-off performances are achieved for co-VARI stiffened skin with prepreg core filler.These results are helpful to optimize processing procedures and fabricate composite structure by coVARI process.

Effects of Ultrasonic Waves during Resin Impregnation on the Mechanical Properties of Unidirectional Composite Materials

Effects of ultrasonic vibrations on mechanical properties of fiber reinforced plastics were investigated during molding resin impregnation process in vacuum assisted resin transfer molding.?The vacuum bag including the preformed each?non-crimp fabrics (carbon and glass fibers)?was placed in a water bath of an ultrasonic wave generator during resin impregnation. The mechanical properties of the laminates were evaluated?through the mechanical strength tests and scanning electron microscope?(SEM) observation. The results revealed that ultrasonic waves improved transverse tensile, flexural, interlaminar shear, and compressive strengths of the carbon fiber (CF) laminates and interlaminar shear and compressive strengths of the glass fiber (GF) laminates. It was found from SEM observation that the fracture modes of the CF and GF laminates processed using ultrasonic waves were resin fracture. Accordingly, the adhesion of the fiber/resin interface was improved by oscillating ultrasonic vibration during resin impregnation, leading to an increase of the interface strength.

基于真空导入工艺的大尺度复合材料异型构件成型技术研究

研究了大尺寸复合材料水滴形截面异型构件的成型工艺。在达西定律的基础上采用实验法测得了玻璃纤维织物渗透率,建立了树脂浸润过程的仿真模型。采用仿真软件对典型构件一体成型充模过程进行仿真分析,分别对中心点注射、中心线注射、单边注射和多线程接力注射方案进行探讨,仿真结果表明,多线程接力注射方案可有效缩短充模时间,满足树脂适用期内完成充模的要求,并达到100%充模率。采用多线程接力注射方案制备了典型构件样机,实际充模时间与理论计算相差约10%,对生产实践具有指导性意义。

孔槽泡沫夹芯复合材料真空辅助树脂传递工艺仿真与优化

本工作提出了孔槽泡沫夹芯复合材料的设计方案并针对真空辅助树脂传递(VARI)工艺进行了实验和仿真研究。首先,通过实验测得玻璃纤维织物和树脂的相关参数,利用Hagen-Poiseuill方程和达西定律算出孔洞和沟槽的等效渗透率;接着,利用PAM-RTM模拟孔槽泡沫夹芯复合材料的VARI工艺过程,并与实验结果进行对比;然后,使用PAM-RTM研究了芯材加工参数、树脂灌注方式和导流网铺敷区域对成型过程的影响,并选出了最优方案;最后,在此方案的基础上研究了树脂黏度与灌注时间的关系,并拟合得到了预测函数。结果表明:实验结果与仿真结果基本一致;最优灌注方案可显著缩短树脂填充时间并降低整体孔隙率;预测函数可准确预测灌注时间,对实际生产具有一定的指导意义。

电泳烘烤对EP/CF及EP/CF/GF复合材料力学性能的影响

采用真空辅助树脂传递模塑(VARTM)工艺制备了不同铺层方式的碳纤维增强聚合物基复合材料(CFRP):环氧树脂/碳纤维(EP/CF)和环氧树脂/碳纤维/玻璃纤维毡(EP/CF/GF)复合材料,重点研究了不同铺层纤维体系的CFRP渗透率以及电泳烘烤前后的力学性能变化,探究了其失效机理。结果表明,[±45°]铺层方式有利于体系中树脂的浸润,且加入GF能够明显提高体系的渗透率;电泳烘烤后,CF[0/90°]、CF[±45°]和CF/GF[±45°]的拉伸强度分别下降了15.65%、12.05%和6.77%,模量分别下降了9.08%、16.39%和10.04%,而CF/GF[0/90°]的拉伸强度和模量则分别提高了7.74%和6.95%;在弯曲性能方面,电泳烘烤后CF[0/90°]、CF/GF[0/90°]、CF[±45°]和CF/GF[±45°]的弯曲强度分别下降了7.62%、8.23%、15.89%和48.39%,模量分别降低了9.23%、3.69%、17.85%和34.38%;而电泳烘烤对4种材料的压缩性能影响较小;电泳后,CF[0/90°]和CF[±45°]的储能模量、损耗模量均有一定幅度提高,CF/GF[0/90°]和CF/GF[±45°]的储能模量、损耗模量均有下降。

基于VARTM的碳纤维单向与三维编织混杂织物树脂灌注工艺

为探究碳纤维单向与三维编织混杂增强环氧树脂基复合材料地铁转向架侧梁的树脂灌注成型工艺,首先基于渗透率理论模型采用非饱和径向流法分别测试得到碳纤维单向与三维编织织物的渗透率。通过数值模拟的方法对典型复合材料方形管结构进行缩比建模与网格划分,并利用PAM-RTM软件对树脂灌注成型过程进行仿真分析,预测了制备复合材料方管所需的灌注时间、灌注压力以及树脂流动过程缺陷的产生。最后根据模拟的灌注方案通过真空辅助树脂传递模塑(VARTM)成型工艺制备了碳纤维单向和三维编织混杂织物增强环氧树脂复合材料方管结构件。结果表明,通过PAM-RTM模拟VARTM工艺制备复合材料方管时树脂的流动,预测得到灌注时间为3897 s,VARTM工艺实际制备复合材料方管的灌注时间为4052 s,误差约为3.8%,在合理误差范围内。方管内部灌注压力随着与注胶口距离的增加而逐渐减小。模拟与实验的误差可能是由于实际铺层和灌注过程中树脂流动引起织物的剪切变形以及真空度的差异导致渗透性能产生变化。仿真模拟和实际制备复合材料方管均无明显缺陷产生,证明径向法织物渗透率的理论模型计算测试和仿真结果具有可靠性。

基于VARI工艺的碳纤维复合材料快速修理飞机铝合金裂纹的研究

考虑到飞机战伤抢修需求,在现有的复合材料胶接修理基础上提出了一种基于真空辅助树脂灌注(VARI)工艺的金属裂纹快速修理方法,通过静力拉伸和疲劳实验将VARI修理工艺与传统湿法胶接修理工艺、机械补强修理工艺进行对比,获得了不同修理工艺下实验件的静强度恢复率、疲劳寿命、修理时间及比静拉伸强度恢复率,借助有限元分析法深入研究了VARI修理件的损伤过程,并以比静拉伸强度恢复率为指标,利用Design Expert软件进一步优化了修理补片参数。结果表明:在三种修理工艺中,VARI修理工艺效果最佳,采用VARI修理的实验件静强度能恢复至完好实验件的90.3%,疲劳寿命相比未修理实验件增长了31.4倍;与传统湿法胶接修理相比,采用VARI修理可将修理时间缩短60.2%;与机械补强修理相比,采用VARI修理可将实验件增重降低53.5%,比静拉伸强度恢复率提高146.6%;对于长度为20 mm的裂纹,补片长度60 mm、宽度64.8 mm、铺层数目四层(即补片厚度1 mm)为最优补片参数。

金属3D打印技术在气辅成型模具中的应用实例

介绍了3D打印技术的发展前景、金属光造型复合加工的原理和优势,一种特殊的金属质感树脂材料的特性,详细分析总结了这种材料对生产的影响,设计出了一副特殊的气体辅助系统成型模具,为此类制品的模具设计和生产制造积累了宝贵的经验。

复合材料的真空辅助成型工艺研究

研究了导流介质、脱模介质等工艺要素对真空辅助成型工艺的影响。结果表明,高渗透率的导流介质和脱模介质均能有效提高树脂的充模速度;所研制的新型导流介质能够有效控制树脂的流动状态。采用真空辅助成型工艺成型的复合材料的性能与模压工艺成型的复合材料的性能相当。

真空导入模塑工艺树脂流动规律研究

研究了导流介质、重力、注射方式和注射管径等工艺参数对真空导入模塑工艺中树脂流动行为的影响。结果表明,真空导入模塑工艺中,主导树脂充模流动速度的是导流介质的渗透率;注射方式改变时,树脂的流动模式和流动速度发生改变;树脂的充模流动速度随着注射管径的增大而增大;树脂的流动倾角越接近竖直方向重力对树脂流动的影响越大。

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。

三维整体夹芯织物增强复合材料的研制

用玻璃纤维在普通二维织机上分别试制经向为V形、X形和蜂窝形3种典型三维整体夹芯织物,利用真空辅助成型工艺研制复合材料夹芯板。为使树脂能较好地渗入织物和纤维内部,对灌注用树脂胶液的组成、配制比例以及树脂黏度等进行了研究,并讨论了三维空芯结构织物中树脂胶液流动过程及气泡形成原因。该复合材料成型工艺能有效地排除在成型过程中产生于织物纤维束之间和纤维束内的气泡。研究结果表明所研制的板材保持了夹芯织物原有的孔形结构、形状与较好的力学性能。

真空导入模塑成型工艺的研究进展

真空导入模塑成型工艺(VIMP)因其具有低成本、环保和适于大型制件一次整体成型等优点而成为复合材料成型制备领域的研究热点,并已广泛地应用于船舶舰艇、风电叶片以及建筑工程材料的制造等领域。介绍了VIMP的工艺原理、特点和技术要求,综述了VIMP工艺中树脂流动行为的研究进展以及VIMP工艺的应用进展,并展望了VIMP工艺的研究方向。

碳纳米管-玻璃纤维织物增强环氧复合材料的结构与性能

通过物理沉积法和静电吸附法在玻璃纤维织物(GF)表面包覆多壁碳纳米管(MWCNTs),制备GF-d-CNTs和GF-a-CNTs两种多尺度增强体,采用真空灌注工艺制备MWCNTs-GF增强环氧复合材料。采用静态、动态力学法、扫描电镜、红外光谱等分析手段,对复合材料的拉伸、弯曲、层间剪切、黏弹性和微观组成结构表征。结果表明:MWCNTs包覆于GF表面形成"倒刺"结构,并通过啮合作用增强了复合材料界面的强度和树脂韧性,提高了复合材料的玻璃化温度(Tg)等;与纯GF复合材料相比,GF-d-CNTs复合材料的拉伸强度和模量分别提高14.5%和37.9%,弯曲强度和模量分别提高26.2%和36.6%,层间剪切强度提高31.5%;GF-a-CNTs复合材料的Tg提高了8.9℃。