热塑性复合材料自动铺放工艺参数分析与优化

热塑性复合材料自动铺放原位成型（AFP）技术是高效低成本制造大型复合材料构件的关键,而自动铺放过程中工艺参数的选取及控制精度对成型构件的性能有较大影响,因此为保证原位成型后成型构件的性能,需分析自动铺放工艺参数对成型构件性能的影响并对其进行优化。本文基于热塑性复合材料自动铺放平台,以连续玻璃纤维增强聚丙烯（GF/PP）预浸纱为原料制备复合材料层合板,以层合板的力学性能为优化目标,根据响应曲面法原理设计试验,分析热气温度、热压辊压力及冷压辊压力各工艺参数及其耦合作用对层合板力学性能的影响,建立各工艺参数与层合板力学性能的二次多项式回归方程预测模型,通过预测值与实际值对比等检验分析,验证回归模型的有效性和可靠性,进而获得热塑性复合材料AFP最优工艺参数组合为热气温度为385℃、热压辊压力为0.3 MPa、冷压辊压力为1.1 MPa。     

自动铺放工艺制备罐外固化复合材料的力学行为

针对碳纤维增强树脂基复合材料IM7/CYCOM5230-1罐外固化预浸料,研究了自动铺放（AFP）罐外固化（OOA）预浸料的制备过程并优化了铺放工艺参数,采用热分析手段研究了CYCOM5230-1树脂固化动力学及黏度特性,在此基础上开发了一种短时固化工艺,并评价了基于此工艺制备的OOA复合材料力学性能。结果表明,AFP铺放过程中预浸料间缝隙会影响OOA复合材料的成型质量,采用铺放压力为180 N、加热温度为50℃、铺放速率为0.20 m/s的铺放参数,可获得表面平整、成型质量优异的复合材料样件。热分析结果表明,罐外固化CYCOM5230-1树脂室温黏度大,满足OOA工艺中真空压实排气需求。短时固化工艺可达到与典型固化工艺相同水平固化度,提升了固化效率,且制备的复合材料可以达到59%的纤维体积分数及低于0.5%的孔隙率,其力学性能与典型固化工艺制备的复合材料相当,并且能够达到热压罐复合材料的水平。     

三维机织复合材料残余应力/应变多尺度分析及工艺参数优化

为预测三维机织复合材料工艺引入的残余应力/应变,提出工艺制度优化方案,建立了一种工艺过程分析的多尺度模型。通过建立纤维尺度及纱线尺度代表体元(RVE),计算了成型过程中纤维纱线及三维机织复合材料的模量演化历程。考虑固化过程中树脂的化学收缩效应,在纱线尺度上开展热-化学-力学耦合分析,预测了细观残余应力-应变及其演化规律。采用三维机织技术,实现了光纤布拉格光栅传感器(FBG)在三维机织预制体中的预埋,并对其树脂传递模塑(RTM)成型过程中的温度、应变历程进行监测,试验结果验证了有限元模型的准确性。采用基于空间信息、误差信息和优化结果的三种序列采样方法,建立了工艺过程分析代理模型,并开展工艺参数优化设计,结果显示采用优化后的工艺参数,残余应变降低了15.4%,工艺周期缩短了10.6%。      

碳纤维/环氧树脂预浸带铺放应力场及制品微观结构的模拟与实验

碳纤维/环氧树脂预浸带复合材料在铺放成型时,由于树脂基体与碳纤维之间的热膨胀系数存在差异以及成型时热-力参数作用下由于纤维的变形而导致纤维与基体接触处产生应力集中等原因,在制品材料中会产生热残余应力。针对碳纤维/环氧树脂预浸带复合材料的实际结构特点,利用ABAQUS有限元软件建立含有界面的碳纤维/环氧树脂预浸带复合材料的细观代表性体积单元(Representative volume element, RVE)有限元模型,采用实验研究和有限元仿真分析的方法,研究在温度-压力参数作用下预浸带铺放制品残余应力的分布规律及影响机理。首先,建立预浸带铺放时的温度和压力模型,研究不同温度和压力参数条件下碳纤维/环氧树脂预浸带铺放制品残余应力的分布情况。其次,采用耦合降温法模拟碳纤维/环氧树脂预浸带残余应力随纤维体积含量、铺放压力以及铺放温度的变化规律,并采用扫描电镜对不同工艺参数条件下预浸带铺放制品的微观结构进行分析。通过对模拟结果进行分析比较得到各因素对制品残余应力的基本影响规律;最后进行不同温度和压力等铺放参数对预浸带铺放成型时残余应力影响的实验测试研究。      

碳纤维复合材料自动铺放关键技术的现状与发展趋势

碳纤维复合材料具有耐高温、耐摩擦、耐腐蚀等诸多优异性能,被广泛应用于航空航天、汽车制造等相关领域.鉴于碳纤维复合材料的广泛应用,制备碳纤维复合材料构件的自动铺放设备及技术也得到了快速发展.近年来,复合材料自动铺放技术也取得了非常显著的成绩.碳纤维复合材料自动铺放技术的研究是铺放设备、铺放轨迹、铺放工艺及铺放软件技术的综合性研究.其中,研究人员将铺放头与纤维纱架结合实现了碳纤维复合材料铺放设备的一体式结构,为完全自动化铺放奠定了基础.碳纤维复合材料的铺放轨迹起初采用相对简单的定角度铺放,但是近些年变角度铺放成为研究热点,采用变角度铺放可以提升铺放构件的力学性能.另外,工作人员针对复合材料的铺放温度、铺放速度和铺放压力等铺放工艺进行了研究,实现了铺放工艺参数的优化并提高了铺放构件的成型质量.此外,在复合材料自动铺放软件技术的研究中,研究人员以铺放工艺及构件形体要求为基础,开发了与铺放设备相匹配的CAD/CAM软件系统,实现了复合材料的自动化、智能化铺放.本文主要从自动铺放设备结构、纤维铺放轨迹规划与控制、铺放工艺参数优化和自动铺放软件系统几个方面对国内外自动铺放技术的研究进展进行了综述.基于自动铺放技术的发展现状,总结了国内自动铺放技术存在的问题,并对国内自动铺放技术的发展方向进行了探讨.     

软包装容器底部折叠成型理论分析与参数设计

以一种平底软包装容器底部的折叠成型为研究对象,通过对包装薄膜折叠成型过程的受力分析,建立了成型装置主要结构参数的理论关系。在基本实验的基础上,进一步探讨了主要结构参数的影响和确定,并通过Pro/E对多目标参数设计实施了进一步的优化,形成了初步的理论设计结果,为折叠成型装置设计提供参考。     

典型曲面构件的VARI工艺模拟分析及实验验证

对典型曲面构件进行了真空辅助成型工艺(VARI)工艺模拟分析,确定了最佳的注射方式及注胶口、出胶口位置,得出了VARI工艺流道设计的几个主要准则,并运用模拟结果开展了可视化实验研究,得到了无缺陷的构件制品。对预成型体铺放过程中剪切变形引起的局部渗透率变化及其对工艺过程的影响进行了研究,研究表明,通过PAM-RTM软件可以计算剪切引起的局部渗透率变化,考虑局部渗透率变化的模拟结果和实验结果较为一致。     

热塑性复合材料纤维铺放工艺的研究进展

热塑性复合材料由于其良好的可焊接性、可循环利用性、抗化学腐蚀性,特别是短时间内就可加工成型等特点,在未来航空航天构件制造领域有着广阔的应用前景。纤维铺放过程中涉及一系列的物理现象,涵盖传热学、热力学、结晶动力学,牛顿流体力学等学科及这些学科的交叉领域。本文以上述学科的相关知识为理论依据,对纤维铺放工艺中的加热工艺,冷却工艺,铺层间强度,纤维铺放压力和残余热应力五方面内容,通过分析其理论模型的建立和求解方法,介绍和讨论了纤维铺放过程中与最终产品质量相关的基体材料结晶度、铺层间紧密接触程度、铺层间熔合度等关键问题及其中涉及的铺放温度、铺放速率、铺放压力等主要工艺参数。同时,本文还总结了国外的研究成果和研究进展,指出其中存在的一些问题,并对今后纤维铺放工艺的研究方向进行了展望。     

复合材料叶片RTM成型缺陷研究

本文简要介绍了复合材料叶片的缺陷类型及其形成机理。综述了国内外在RTM工艺成型过程中纤维浸润和气泡形成方面的研究现状,对缺陷的排除方法进行了分析总结。     

纤维增强复合材料自动化成型中织物变形研究进展

纤维增强树脂基复合材料具有高比强度和高比刚度等优异特性，被广泛应用于汽车领域以实现汽车轻量化。然而，纤维织物的多尺度特性使其在复杂形状的车身零部件成型中变形机制十分复杂，极易产生成型缺陷，削弱成型后的复合材料力学性能。表征织物变形特性，揭示织物变形机制，是准确预测织物复杂形状成型，指导织物成型工艺参数合理设计的重要基础。因此，本文针对织物在成型过程中的压缩、剪切、弯曲和滑移4种关键变形特性及在复杂几何形状中成型特性的研究进展进行综述，详细介绍了织物上述变形和成型特性的研究方法及研究热点。本文将为织物的变形机制研究、复杂形状成型精准预测和工艺参数合理设计提供指导，推动复合材料在汽车领域中的大规模应用。     

复合材料自动铺丝工艺参数对应力波传播特征的作用机制

利用应力波特征能够有效识别材料结构中内部缺陷及其分布形式,为了将工艺载荷作为应力波激励源对预成型体内部缺陷进行识别,应首先研究铺丝过程中工艺参数对应力波传播特征的影响,以确定应力传感器的放置位置。本文采用有限元方法构建了铺丝过程热力耦合模型,分析了应力波特征参数与工艺参数之间的关系,并进行了实验验证。为了从微观能量角度解释工艺参数对应力波特征的影响规律,采用分子动力学方法,建立了预浸丝界面的分子模型,并计算出总能量、纤维表面能、基体内能等能量参数,识别和评价了不同工艺参数作用下的应力波驱动能量及其贡献比,以揭示工艺参数对应力波特征的能量作用机制。结果表明,以基体内能作为驱动能量的侧向应力波与工艺参数的关系明显,在不同工艺参数施载下,内部缺陷的形成对该波形的作用易于识别,该结论可作为应力传感器放置位置的参考依据。      

Machining and surface integrity of fibre-reinforced plastic composites

The current focus of manufacturing research on fibre-reinforced plastics (FRP) is composed of the search for efficient processing techniques capable of providing high quality machined surfaces. Very limited work has been performed to identify the influence of manufacturing processes like edge-trimming and drilling on material performance. Recent reports suggest that process-induced damage may affect the mechanical behaviour of FRP materials. Therefore an experimental study of orthogonal cutting was conducted on the edge trimming of unidirectional and multi-directional graphite/epoxy composites with polycrystalline diamond tools. The effects of tool geometry and operating conditions were evaluated from an analysis of chip formation, cutting force, and machined surface topography. All aspects of material removal were found to be primarily dependent on fibre orientation. Discontinuous chip formation was noted throughout this study, regardless of machining parameters. Three distinct mechanisms in the edge trimming of fibre-reinforced composite material including a combination of cutting, shearing, and fracture along the fibre/matrix interface were observed. An investigation conducted on the compression, flexural and impact strength of graphite/epoxy composites machined by both traditional and non-traditional techniques, confirms that manufacturing characteristics may not only affect bulk properties but also influence the initiation and propagation of failure.     

选区激光熔化中飞溅行为的研究进展

选区激光熔化技术(SLM)被认为是极有前途的增材制造技术之一,但不可逆的溅射行为严重限制了SLM技术的应用。从粉末熔池演变、加工工艺优化和飞溅颗粒动态特征监测等方面,总结了SLM过程中飞溅行为的研究现状,分析了飞溅行为的产生机制,探讨了激光–粉末–熔池相互作用下的熔池演变情况,表明金属蒸气、Marangoni效应和伯努利效应是诱发飞溅的主要因素;讨论了加工工艺与飞溅行为的相互关系,表明通过优化工艺参数和改善打印环境以抑制飞溅是行之有效的方法;阐述了飞溅诱导缺陷的机理,并讨论了SLM过程的监测方法,表明单一信号的局限性会导致监测结果失准,多信号融合监测是提升精准性的重要方法之一。最后,针对飞溅行为存在的关键科学问题和技术难题,展望了SLM加工中飞溅行为的研究方向。     

Additive manufacturing of steel-copper functionally graded material with ultrahigh bonding strength

Additive manufacturing enables processing of functionally graded materials (FGMs) with flexible spatial design and high bonding strength.A steel-copper FGM with high interfacial strength was developed using laser powder bed fusion (LPBF).The effect of laser process parameters on interfacial defects was evaluated by X-ray tomography,which indicates a low porosity level of 0.042 ％ therein.Gradient/fine dendritic grains in the interface are incited by high cooling rates,which facilitates interface strengthening.Multiple mechanical tests evaluate the bonding reliability of interface;and the fatigue tests further substantiate the ultrahigh bonding strength in FGMs,which is superior to traditional manufacturing methods.Mechanisms of the high interfacial bond strength were also discussed.     

First steps towards an advanced simulation of composites manufacturing by automated tape placement

Composite materials and their related manufacturing processes involve many modeling and simulation issues, mainly related to their multi-physics and multi-scale nature, to the strong couplings and the complex geometries. In our former works we developed a new paradigm for addressing the solution of such complex models, the so-called Proper Generalized Decomposition based model order reduction. In this work we are summarizing the most outstanding capabilities of such methodology and then all these capabilities will be put together for addressing efficiently the simulation of a challenging composites manufacturing process, the automated tape placement.     

Influence of pressure-assisted polymerization on the microstructure and strength of polymer-infiltrated ceramics

A method of manufacturing polymer-infiltrated ceramics (PICs) is to pre-infiltrate a porous ceramic with a liquid monomer and subsequently polymerize the organic component inside the ceramic structure. The volume reduction during polymerization leads to the formation of pores (defects), which has a detrimental effect on the mechanical properties of PICs. To avoid the generation of defects, a new polymerization method that uses pressure during polymerization was developed. To investigate the influences of pressure and heating rate on strength and microstructure, both parameters were varied. The influences of both parameters on the strength of PICs were studied using a biaxial test. The influence on the microstructure was investigated through microscopy. Fracture toughness and R-curve behavior of the manufactured PICs were determined with the SEVNB method. The process parameters have a strong influence on strength and microstructure of PICs. Defect-free PICs with improved strength could be manufactured using elevated pressure during polymerization. As expected, a distinct R-curve behavior and enhanced fracture toughness relative to composites manufactured using conventional methods was found. The developed manufacturing method leads to defectless PICs with increased mechanic behaviors.     

Axiomatic modelling of agile production system design

The manufacturing organisations are witnessing a transformation in the manufacturing paradigm due to increasing competition. Agile manufacturing (AM) is a contemporary manufacturing paradigm which enables the organisations to survive in this competitive scenario. Design engineering is a vital technological enabler of AM. The research on axiomatic design in the field of AM is found to be feeble. In this context, this paper reports an axiomatic model of agile production system design using process variables. A hierarchical structure has been developed to model the design process of an agile production system composed of functional requirements, design parameters and process variables. In the theory of axiomatic design, process variables are created by mapping the design parameters in the process domain. This article serves as an efficient guideline for the design process to clarify the tools, methods and resources of designing agile production system of Indian electronic switches manufacturing organisation.     

Environmental stress-corrosion cracking of fiberglass: lessons learned from failures in the chemical industry

Fiberglass reinforced plastic (FRP) composite materials are often used to construct tanks, piping, scrubbers, beams, grating, and other components for use in corrosive environments. While FRP typically offers superior and cost effective corrosion resistance relative to other construction materials, the glass fibers traditionally used to provide the structural strength of the FRP can be susceptible to attack by the corrosive environment. The structural integrity of traditional FRP components in corrosive environments is usually dependent on the integrity of a corrosion-resistant barrier, such as a resin-rich layer containing corrosion resistant glass fibers. Without adequate protection, FRP components can fail under loads well below their design by an environmental stress-corrosion cracking (ESCC) mechanism when simultaneously exposed to mechanical stress and a corrosive chemical environment. Failure of these components can result in significant releases of hazardous substances into plants and the environment. In this paper, we present two case studies where fiberglass components failed due to ESCC at small chemical manufacturing facilities. As is often typical, the small chemical manufacturing facilities relied largely on FRP component suppliers to determine materials appropriate for the specific process environment and to repair damaged in-service components. We discuss the lessons learned from these incidents and precautions companies should take when interfacing with suppliers and other parties during the specification, design, construction, and repair of FRP components in order to prevent similar failures and chemical releases from occurring in the future.     

飞机复杂曲面蒙皮零件充液拉深技术研究

目的研究充液拉深工艺参数对飞机复杂曲面蒙皮零件成形质量的影响规律。方法以飞机灯罩蒙皮零件为研究对象,结合材料力学特性分析了零件的工艺性。基于破裂和起皱失稳条件理论研究了零件的加载工艺窗口,利用有限元方法分析了零起皱和破裂等缺陷,通过优化工艺参数和拉延筋参数获得了合格的构件。结果基于仿真优化结果,进行了模具设计和工艺验证实验,分析了实际充液拉深过程中缺陷产生的原因,为落差较大蒙皮零件的精密制造提供参考。结论对于具有多特征的复杂零部件,过渡曲面易产生起皱缺陷,仅通过调整液室压力或毛料尺寸的方法无法在保证不发生拉裂和贴模问题的前提下消除起皱缺陷。通过设置拉延筋来增加材料流动阻力、控制材料流动,可以消除过渡区域的起皱缺陷。