自动铺丝过程中预浸料的侧向弯曲

根据自动铺丝过程中预浸料的受力特点,建立预浸料的侧向弯曲变形模型。利用最小势能原理、瑞利-利兹法以及相关的复合材料力学理论,推导出预浸料侧向屈曲半径公式。研究自动铺丝温度、压力、速度、黏附力等主要工艺参数对侧向弯曲性能的影响,并用自动铺丝机铺放不同半径的预浸料圆弧进行验证。结果表明:随着温度增大、压力和速度减小,预浸料的侧向弯曲性能提高;增加预浸料黏附力可显著提高其侧向弯曲性能,符合理论分析结果。     

自动铺放过程双马树脂预浸料温度与黏度

通过对自动铺放成型工艺的分析,探索了自动铺带成型过程中预浸料温度对复合材料黏性的影响规律。对影响预浸料温度的热风温度和铺放速度两个因素进行了研究,从理论上建立了热风加热温度和铺放速度与预浸料温度之间的关系,提出了控制预浸料温度的具体实施方案,指导自动铺带成型过程。根据双马树脂预浸料黏度和温度曲线,分别在不同的热风温度和铺放速度条件下进行实验,得到在热风温度为90℃、铺放速度为10~20m/min时,预浸料黏度满足铺覆性要求,验证了预浸料热风温度和铺放速度对复合材料制品质量的影响,为自动铺带工艺提供参考。     

自动铺丝用预浸窄带的质量分析及其影响因素

近年来随着自动铺丝技术的快速发展和应用,对预浸窄带的需求量增加,但国内研究人员对有关预浸窄带质量的评价体系和分析方法尚未形成统一共识。本文采用多种方法对预浸窄带的质量进行了全面分析。通过图像法及称重法分析发现,国产窄带的宽度均匀性、接头处纤维平齐度、边缘断丝情况等分切质量均控制较好。研究了间歇式热压工艺和连续式辊压工艺对窄带接头质量的影响,通过拉剪强度和剥离强度分析发现,压接工艺温度和时间是影响其力学的关键因素,对比而言辊压工艺制得的接头性能较热压工艺具有更好的稳定性。同时,接头性能也受测试环境影响,其中环境湿度的作用大于温度。随着室温储存时间延长,窄带接头的力学性能先上升后下降,通过差热分析和红外光谱分析发现,这与界面处树脂的化学反应和固化程度增长密切相关。最后,对接头反复过辊后的疲劳损伤分析表明,接头处的拉剪强度随过辊温度、张力及圈数增加而下降。     

硅橡胶热膨胀工艺预浸料铺层内树脂压力变化规律

采用硅橡胶热膨胀工艺制备了碳纤维/双马树脂复合材料层板, 通过自行设计的成型模具及树脂压力在线测试系统测试并分析了成型过程中热胀压力和预浸料铺层内树脂压力的变化规律, 考察了工艺间隙和温度分布的影响, 并通过显微观察分析了不同工艺条件下层板的密实状况。结果表明: 采用树脂压力在线测试系统, 可实现热膨胀工艺预浸料铺层内树脂压力的测试; 工艺间隙和硅橡胶内的温度分布对树脂压力及硅橡胶的热胀压力有重要影响, 在零吸胶工艺条件下, 当工艺间隙设计合理时, 凝胶前热胀压力和树脂压力的变化趋势及变化程度基本一致, 固化层板纤维密实并且厚度均匀; 通过增加恒温平台减小硅橡胶内部温差, 可使热胀压力的增加速度减小。      

纤维增强热塑性树脂预浸料的制备工艺及研究进展

热塑性复合材料因冲击韧性高、环境适应性强、可回收利用等优点,被广泛应用于汽车制造、航空航天、国防军工等领域。但因热塑性树脂加热熔融后较高的黏度使其很难与纤维充分浸渍。预浸料作为制造复合材料的中间材料,现阶段制备工艺已相对成熟,预浸料中纤维已被树脂浸润,因此通过预浸料制备的复合材料孔隙率较低。本文介绍了现阶段常用的热塑性预浸料制备方法及各自的优缺点,包括溶液浸渍法、熔融浸渍法、粉末浸渍法、薄膜叠层法、纤维混杂法以及反应链增长浸渍法。阐述了热塑性树脂熔体浸润纤维的浸渍机理,对浸渍机理的部分研究成果进行了概括。概述了浸渍温度、浸渍压力和牵引速率对预浸带性能的影响。最后指出了国内预浸料生产中存在的主要问题,未来可采用多学科结合、纤维树脂改性、对浸渍过程进行计算机模拟等方法促进热塑性预浸带的产业化发展。     

预浸料的质量控制

预浸料的原料质量尤其是树脂质量是保证预浸料性能的基础,在预浸料制备过程中,及时、有效、无损的在线监测是预浸料发挥性能的保证。简要介绍了几种常用的在线监测手段,包括β射线监测、超声波监测、红外光谱监测及近红外光谱监测等。此外,预浸料成品的质量控制是复合材料性能的关键,其中凝胶时间、树脂流动性、挥发分含量、树脂含量、单位面积纤维质量等是预浸料重要的质量指标。     

预浸料的制备工艺及应用

本文介绍了国内外热固性预浸料和热塑性预浸料的制备工艺和预浸料典型厂家、产品及应用。     

热熔胶膜法制造预浸料对复合材料力学性能的影响

讨论了热熔胶膜法制备了３２３４／Ｇ８０３ＰＶ预浸料对其复合材料弯曲强度，弯曲模量和层间剪切强度及其保持率的影响，指出使用热熔法制备预浸料可以提高复合材料的耐湿热性。     

热熔法制备大丝束炭纤维预浸料工艺研究

简要介绍了热熔法制备大丝束炭纤维(60K)预浸料的工艺过程,并着重对影响预浸料质量的几个主要因素进行了讨论,结果表明,严格控制预浸温度、纤维张力、预浸压力和运行速度等因素是保证大丝束炭纤维充分展开和浸润的技术关键.     

碳纤维增强双马来酰亚胺树脂预浸料铺覆黏性及其储存老化行为

将碳纤维增强双马来酰亚胺树脂预浸料CCM40J/HT-280分别置于4种储存环境（真空、N₂、O₂、空气）进行室温老化实验,研究了预浸料铺覆黏性与储存环境和老化时间的关系,对不同环境下黏性失效前后的样品进行了DSC、流变、红外光谱分析。针对不同黏性级别的预浸料,采用热压罐成型工艺制备了复合材料层合板,对层合板内部成型质量及复合材料力学性能进行了研究。结果表明,真空和N₂环境储存下的CCM40J/HT-280预浸料黏性失效周期相比于O₂与空气中的样品延长约40%。DSC和流变测试结果表明,老化后树脂的交联程度大于新鲜树脂,树脂最低黏度也显著增大,O₂环境下的样品表现的更为明显;对红外光谱特征峰分析表明,O₂环境储存条件下树脂交联反应程度高于真空环境,说明O₂对双马来酰亚胺树脂室温下的老化具有促进作用。黏性失效的预浸料制备的CCM40J/HT-280复合材料内部多为层间或层内的密集孔隙,其弯曲强度下降约13.0%、弯曲模量下降约6.5%,层间剪切强度下降约10.7%。      

Effect of room-temperature out-time on tow impregnation in an out-of-autoclave prepreg

Tow impregnation as a function of material out-time was investigated for an out-of-autoclave carbon fiber–epoxy prepreg. Prepreg was aged at ambient temperature for 56 days. Every 7 days, laminates were laid up and cured using vacuum bag only processing. Void content was calculated through image analysis of polished sections. Experimental results were used to validate an analytical model for tow impregnation. Model predictions were based on flow kinetics during processing conditions, taking into account increasing degree of cure and evolution of resin viscosity as a function of ambient aging time. The study found that no significant tow porosity occurred within the material’s stated out-life, that tow porosity increased once this out-life was exceeded and eventually stabilized due to the room-temperature vitrification of the resin. The model’s predicted trends were consistent with experimental results, suggesting that an increase in resin viscosity is indeed the main cause of out-time induced tow porosity and providing a means of predicting laminate quality as a function of room temperature aging time.     

纤维铺放压紧力及预浸带加热温度对复合材料力学性能的影响

采用三因素四水平正交实验与单因素实验相结合, 通过力学性能测试及SEM和光学显微镜微观形貌观察研究了复合材料铺放过程中压紧力、 预浸带加热温度及芯模温度对复合材料力学性能的影响。实验结果表明: 压紧力与加热温度对层间剪切强度(ILSS)影响很大, 而芯模温度影响较小; 当压紧力为600 N、 预浸带加热温度为30℃、 芯模温度为18℃时, 复合材料综合力学性能达到最佳。微观形貌观察结果表明: 随着压紧力和预浸带加热温度升高, 纤维与树脂接触充分, 树脂与纤维分布均匀性较好, 层间富树脂区的厚度较小, ILSS逐渐增加; 但当预浸温度上升到40℃以后, 压紧力作用导致树脂与纤维的分布均匀性变差, 层间富树脂区的厚度较大, 从而导致ILSS下降。     

Modelling the effect of material properties and process parameters on tow impregnation in out-of-autoclave prepregs

Out-of-autoclave prepregs based on woven fabrics initially consist of dry tows and resin-rich areas. The tows allow air evacuation in the initial stages of processing and are subsequently infiltrated by surrounding matrix. The following study analyzes the relationship between material properties, process parameters and tow impregnation for three OOA prepregs. First, a representative model for tow impregnation is developed. Then, the model parameters are determined and the model predictions are correlated to impregnation data measured by X-ray microtomography. Finally, the model is used in a parametric study to investigate the effect of fibre architecture, cure cycle temperature and resin initial degree of cure on tow impregnation rate and to predict the possible occurrence of flow-induced micro-voids.     

Influence of heavy haul railway curve parameters on rail wear

With the use of virtual prototype technology, a heavy haul vehicle-track dynamic model was established and the influence of curve parameters (including curve radius, circular curve length and transition curve length) and track parameters (including superelevation and rail cant) on rail wear was researched. The measures to reduce wear from optimizing curve parameters were summed up, by means of the analysis to the comparisons of a variety of parameter combinations. The study results prove that: when the curve radius is less than 800 m, the curve radius has a great influence on rail wear and the length of transition curve does too. When the curve radius is around 600 m (which means that the curve is a small radius curve), increasing the rail cant of the inner rail to 1/20 will effectively reduce the wear of the curve rail, and setting the inadequate superelevation to around 20% less than the balanced superelevation will, too. When the curve radius is around 800 m, increasing the rail cant of the inner rail to 1/20 will effectively reduce the wear of the curve rail, and setting the inadequate superelevation to around 10% to 15% less than the balanced superelevation will, too. When the curve radius is greater than 1000 m, only increasing the rail cant of the inner rail to 1/20 can effectively reduce the wear of the curve rail.     

结构参数对费马型线柔性弹簧性能的影响分析

基于一种费马曲线的柔性弹簧,设计出不同略角、厚度、弹簧臂数和槽首尾封闭方式的多种柔性弹簧.利用ANSYS软件对多种几何参数的费马型线柔性弹簧进行了有限元分析,通过分析不同参数的费马型线柔性弹簧的最大应力值和径、轴向刚度的变化特性,总结了略角、厚度等结构参数对费马曲线柔性弹簧性能的影响规律;通过改变槽首尾端封闭方式实现了...     

Influence of minimum quantity lubrication parameters on grind-hardening process

Currently, dry grind-hardening has been studied to achieve a deep grinding harden layer. For dry grind-hardening process, the ground surface may have a poor surface quality. In our previous research, minimum quantity lubrication (MQL) has been proved as an effective way to improve the surface quality in grind-hardening process. Unfortunately, the relationship between the surface quality and parameters of MQL is still not clear. In this paper, different spraying parameters (fluid flow, air pressure, nozzle location, spraying distance) are investigated in surface grinding experiments of annealed steel AISI 5140. Grind-hardening performances are analyzed for grinding force and surface quality, such as surface roughness, micro-hardness, and grinding harden layer depth. Consequently, the results show that MQL can improve the grinding surface roughness and the micro-hardness of the grinding harden layer. The surface roughness can be improved with a better lubrication, which can be achieved with the appropriate spray direction. The surface roughness and the harden layer depth are reduced with the increasing fluid flow rate and air pressure, while they increase with the spraying distance.     

焊接参数对搅拌摩擦焊接质量的影响

采用基于固体力学的有限元方法建立了搅拌摩擦焊接过程的三维数值模型,研究了在焊接参数不同的情况下搅拌摩擦焊接过程中力学特征的变化．数值模拟结果和试验结果都表明,等效塑性应变能近似地反映焊接构件焊缝区域材料显微结构的演化,较高的搅拌头转速和较低的焊速有利于提高焊缝的质量．焊接构件特定的等效塑性应变等值线可以较好的对应不同焊接区域的边界．随着搅拌头转速的提高,等效塑性应变随之增大,但搅拌探针与焊接构件交界面上的接触压力随之减小．等效塑性应变随着搅拌头平移速度的增大而减小．     

RTM和预浸料共固化树脂体系界面层特性

RTM和预浸料两种工艺共固化会形成一个界面层, 采用差热分析和红外光谱研究环氧树脂/酸酐和环氧树脂/双氰胺共固化体系的反应, 采用正电子湮没技术测试了共固化体系所形成界面中的自由体积尺寸和浓度。结果表明, 单独体系的反应峰大约是160 ℃, 两种工艺树脂混合后, 反应峰向高温方向移动, 为275.14 ℃; 同时放热量从RTM体系的236.2 J/g和预浸料体系的193.9 J/g降低至83.15 J/g; 界面层的自由体积尺寸和浓度比两个单独固化体系的大, 弯曲强度分别从RTM体系的140.2 MPa和预浸科体系的105.4 MPa降至83.4 MPa。两种体系的固化剂相互反应, 致使共固化体系反应不完全, 形成一个力学性能较低的共固化界面层。     

RTM和预浸料共固化树脂体系界面层特性

RTM和预浸料两种工艺共固化会形成一个界面层,采用差热分析和红外光谱研究环氧树脂/酸酐和环氧树脂/双氰胺共固化体系的反应,采用正电子湮没技术测试了共固化体系所形成界面中的自由体积尺寸和浓度.结果表明,单独体系的反应峰大约是1 60℃,两种工艺树脂混合后,反应峰向高温方向移动,为275.14℃;同时放热量从RTM体系的236.2 J/g和预浸料体系的193.9 J/g降低至83.15 J/g;界面层的自由体积尺寸和浓度比两个单独固化体系的大,弯曲强度分别从RTM体系的140.2 MPa和预浸科体系的105.4MPa降至83.4 MPa.两种体系的固化剂相互反应,致使共固化体系反应不完全,形成一个力学性能较低的共固化界面层.     

Influence of drilling process parameters on hybrid vinyl ester composite

In the modern world, the use of hybrid composite becomes unavoidable. They have their unique and tailor-made properties which makes them suitable for many engineering and industrial applications. But the restriction on the use of composites arises during machining of these composites. Unlike conventional materials, machining of composites is a tedious process due to their anisotropic nature. In the current research work, the prepared high strength hybrid composite is subjected to one of the important machining process say drilling and the process parameters are optimized for the multiple output characteristics namely delamination, torque and thrust force. Taguchi technique aided with grey relational analysis is used for optimization purpose. From the experimental outcome, it is clear that the machining characteristics can be improved at optimum machining conditions. And it is also found that the diameter of the drill has the major effect on the output characteristics.