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.     

热塑性复合材料自动纤维铺放装备技术

基于热塑性复合材料(TPC)自动纤维铺放(AFP)原位固结技术,开展热塑性复合材料AFP装备技术研究,分析AFP平台的功能需求,提出平台总体规划方案,设计开发热塑性复合材料自动铺丝头,并提出预浸纱张力控制方案、精确送纱及温度闭环控制方案。在此基础上,设计AFP系统可行性验证实验,证明方案的可行性和平台的实用价值。结果表明:本实验平台针对热塑性复合材料铺放特点,优化张力与铺放速度匹配,实现预浸纱动态恒张力铺放,确保成型构件质量;实验平台调控铺放速度与送纱协调,实现精确定位,保障成型构件尺寸;建立了铺放速度与加热功率、热流分布关系,实现高精度温度场分布控制。虽AFP成型构件的力学性能比热模压成型构件的力学性能低约20%,但为热塑性复合材料AFP装备技术的广泛应用奠定了基础。     

干纤维自动铺放-液体成型技术进展研究

相较于传统预浸料预制体需要热压罐固化，干纤维自动铺放结合液体成型技术可以实现非热压罐制造复合材料，从而降低制造成本、缩短制造周期。本研究针对干纤维自动铺放-液体成型技术，从干纤维铺放材料、干纤维自动铺放设备以及干纤维自动铺放工艺技术进展三个方面进行概述，并对其未来在船舶领域的应用进行展望。     

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。      

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。     

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。     

基于自动铺放技术的高精度变刚度复合材料层合板屈曲性能

基于自动铺放技术制备的曲线变刚度复合材料层合板,通过定制面内刚度,可有效提高结构的抗屈曲性能。在铺放过程中,铺放轨迹的路径规划是实现变刚度设计的关键技术之一。鉴于此,本文分别以纤维角度线性变化曲线、等曲率曲线及二次Bezier曲线构成的纤维轨迹为研究对象,对其压缩屈曲性能进行参数化分析。并利用有限元模型研究了铺丝头上丝带宽度对层合板型面精度和抗屈曲力学性能的影响。结果表明:在压缩工况下,二次Bezier曲线路径的抗屈曲性能最佳,等曲率曲线路径受曲率约束的影响最小。铺丝头丝束宽度一定,丝带宽度与重叠区域面积和抗屈曲性能呈负相关。使用最大的丝带宽度可最大程度地减小重叠区域面积,提高结构的型面精度,同时保证结构屈曲性能提高37.3%。      

基于自动铺放技术的热塑性复合材料原位固化成型研究进展:热传导行为及层间性能

纤维增强复合材料具有轻质、高强、性能可设计等特性,在减重、抗疲劳、耐腐蚀、维修性等方面明显优于传统金属材料,在航空航天、交通运输、国防等领域的应用越来越广泛,其中热塑性复合材料具有高韧性、高冲击性、无限储存周期、可回收利用等众多优点。复合材料自动铺放技术成型效率高、自动化程度高,特别适用于大尺寸和复杂构件的制造。同时,热塑性复合材料原位固化技术不断发展和进步,生产效率显著提高,生产成本降低,构件质量得以提升。因此,基于自动铺放技术的热塑性复合材料原位固化成型将会是未来大飞机主承力部件的重要成型方法。然而,热塑性复合材料铺放成型过程经历高温制造,伴随着热力学耦合等相关问题。对于原位固化方法,热源的选择颇为关键,将直接影响铺放成型的效果和效率。在铺放成型过程中,热塑性聚合物分子链受热发生流动,宏观上则是热塑性树脂发生从固态到熔融态再到固态的物理变化。整个成型过程持续时间较短,但又涉及一系列的物理变化,是一个非常复杂的过程,目前已成为国际上高性能热塑性复合材料的研究热点之一。热塑性复合材料纤维铺放成型常用的热源主要包括热空气、激光、超声波、电子束等。其中针对热空气的研究较早,建立了铺层内的热传导理论模型,就铺层基层中温度场展开了许多工作并取得了相应的成果。对激光加热成型获得的铺放构件的诸多研究表明,激光作为热源相比于热空气可以大幅提升层间性能。此外,学者们还提出了不同的理论模型来预测最终的熔合强度,但测试结果显示铺放构件的力学性能不及热压罐固化的构件,进一步的理论和实践探索仍然很有必要。本文主要聚焦基于预浸料自动铺放技术的热塑性复合材料原位固化成型工艺,从工艺过程中的热传导行为、铺层的性能指标两方面介绍或探讨了铺放工艺过程、热传递模型、原位固化热源、铺层间紧密接触度、熔合度及熔合强度等的研究现状。     

纤维取向对TC4/PEEK/Cf层板抗高速冲击性能的影响

为研究高速冲击条件下TC4/PEEK/Cf层板破坏失效行为和机理,采用空气炮高速冲击试验探索了纤维取向对层板抗高速冲击性能的影响,并建立了误差有效控制的有限元模型。使用验证后的模型对不同变量下层板冲击试验进行算例丰富。试验和模拟结果表明：TC4/PEEK/Cf层板高速冲击下损伤模式主要是金属/复合材料界面分层、复合材料内部层间分层、金属塑性变形、复合材料撕裂断开等。通过对比不同纤维取向层板高速冲击破坏特征发现,TC4/PEEK/Cf层板抗高速冲击性能与纤维铺放角度有关。层板整体耗散冲击能量的性能随纤维交叉角度增大而提高,纤维单向铺放层板的弹道极限和能量耗散率最低,0°/90°纤维取向层板的弹道极限和能量耗散率最高,抗冲击性能最优。     

变刚度复合材料开孔板拉伸行为数值模拟及试验验证

纤维曲线铺放是提高复合材料构件力学性能的有效方法之一。本文针对复合材料开孔板铺放轨迹进行了研究,利用B样条曲线插值拟合获取了开孔板最大主应力铺放轨迹,并通过离散网格法建立了变刚度开孔板模型,通过引入Tsai-Wu损伤失效判据以及常刚度退化准则,进行了拉伸失效数值模拟及损伤失效分析,并分别铺放了两组常刚度和变刚度开孔板试验样件,进行了拉伸对比试验。结果表明：数值模拟与实验数据吻合较好,变刚度开孔板相比常刚度开孔板,拉伸强度提升了26.92%,且两者损伤失效演化过程显著不同。     

An Experimental Study of the Influence of in-Plane Fiber Waviness on Unidirectional Laminates Tensile Properties

As one of the most common process induced defects of automated fiber placement, in-plane fiber waviness and its influences on mechanical properties of fiber reinforced composite lack experimental studies. In this paper, a new approach to prepare the test specimen with in-plane fiber waviness is proposed in consideration of the mismatch between the current test standard and actual fiber trajectory. Based on the generation mechanism of in-plane fiber waviness during automated fiber placement, the magnitude of in-plane fiber waviness is characterized by axial compressive strain of prepreg tow. The elastic constants and tensile strength of unidirectional laminates with in-plane fiber waviness are calculated by off-axis and maximum stress theory. Experimental results show that the tensile properties infade dramatically with increasing magnitude of the waviness, in good agreement with theoretical analyses. When prepreg tow compressive strain reaches 1.2%, the longitudinal tensile modulus and strength of unidirectional laminate decreased by 25.5% and 57.7%, respectively.     

Fiber path definitions for elastically tailored conical shells

Elastic stiffness tailoring of laminated composite panels by allowing the fibers to curve within the plane of the laminae has proven to be beneficial and practical for flat rectangular plate designs. In this paper the field of application of this variable-stiffness concept is extended to three-dimensional conical shells with arbitrary dimensions that can be fabricated using advanced fiber placement machines. This paper presents the detailed derivation of four theoretical fiber path definitions for generalized conical shell surfaces. The different path definitions and resulting laminate geometries are discussed. Implementation of fabrication details and constraints in terms of the steering radius of curvature based on advanced tow-placement technology are demonstrated.     

碳纤维增强聚苯硫醚复合材料激光加热原位成型过程中的温度场

连续纤维增强热塑性复合材料（Thermoplastic Composite,TPC）自动铺放（Automated Fiber Placement,AFP）可以实现铺层原位成型,因此在制造大型结构件、降低加工成本及提升生产效率方面潜力巨大。原位成型过程中铺层温度场分布对复合材料构件成型质量具有较大影响,且激光加热过程中又涉及激光能量场与预浸料吸收光能后产生的温度场之间相互耦联,机理复杂,因此结合传热模型,通过有限元模拟仿真研究激光辅助加热自动铺放成型连续碳纤维增强聚苯硫醚（CF/PPS）复合材料过程中铺层经历的温度历程。同时构建铺层温度场测量系统,对铺层经历的温度历程进行实时采集和存储。研究结果表明,铺放过程中黏合区域前方存在激光辐照阴影区,使压辊下方黏合区域的温度急剧下降;随着铺放速度的增加,黏合区域峰值温度逐渐降低,且成型速度越快,铺层间黏合区域峰值温度差越小,而热电偶测量结果与仿真结果相差越大;随着激光输出功率的增大,铺层峰值温度逐渐升高;为提高原位成型效率,当激光输出功率选择最大6kW时,最大铺放速度为0.75 m/s。通过对比,试验结果中的峰值温度与仿真模拟结果变化趋势相近,证明了有限元仿真模型的正确性。      

用于FRP固化在线监测的光纤微弯压力传感器

无论在军事还是航空航天领域,光纤传感器都是一种极具应用前景的智能化监测手段。目前,将光纤传感器用于纤维增强树脂基复合材料固化过程的监测的研究是一个热点。但由于大多数光纤传感器监测固化过程成本较高,所以还没有被广泛的应用于实际生产当中。开发了一种新型的低成本、高灵敏度、易操作的光纤传感器用于纤维增强树脂基复合材料固化过程的在线监测。光纤传感器的设计基于光纤微弯损耗原理,其监测的直接目标参量为增强纤维所构成的网络所承担的压力变化,可以进而通过Gutowski的树脂流动/纤维变形理论间接得出对于固化过程中的几个关键参量。给出了这种压力传感器的设计制作方法,测定该种传感器在静态和动态下的压力-光损耗响应曲线,分析了该传感器对环境温度与折射率变化的响应。完成了利用微弯压力传感器进行纤维增强复合材料在热压釜中固化成型过程的在线监测实验,获得了良好的结果。     

Numerical analysis of thermoplastic composites laser welding using ray tracing method

Laser technology is a good alternative for continuous joining of thermoplastics composites structures. Presence of continuous fibers at a high fiber volume fraction (superior to 30%) does not allow using traditional development as for pure thermoplastic materials, due to the presence of fiber clusters or polymer rich areas. Those heterogeneities induce macroscopic light scattering through the structure, reducing the resulting energy level absorbed at the welding interface. The study proposed here takes into account the real microstructure of the composite in order to evaluate changes in local energy diffusion directly linked with local fiber arrangements. The objective of this work is to develop an affordable numerical simulation of the laser welding process modeled with adapted physics mechanism and taking into account the microstructure heterogeneity of the considered materials regarding optical and thermal properties. To model the optical path of the laser beam through the composite fibrous structure, a simulation tool based on geometrical optic is developed. Weldability is considered on composites with different thicknesses, showing the non linear relationship between welding energy and substrate thickness.     

Filament Winding Controller Requirements and B-Spline Solution

Filament winding is a process of placement of reinforcement fibers on to a rotating surface in a specified geometric patern. A conventional straight line interpolation controller is not very appropriate for filament winding because the fiber pay-out-eye is at some distance away from the mandrel surface and its movement from one point to another disturbs the previous fiber positions on the mandrel. Also, the speed of carriage movement is much higher in filament winding and path accuracy requirements are not as high as in conventional cutting machines. Filament winding demands a controller which can produce fast and smooth carnage movements, and have a look-ahead capability so that while moving around curvatures the effect of pay-out-eye movement on previous fiber positions is minimal. This problem can be overcome by using an interpolation technique which determines the profile by considering more than two data points, and whose derivative is continuous in nature. In this project an IBM PC based filament winding controller, using B spline interpolation technique, is developed. Its performance is tested and compared with straight line interpolation controller on a three axis filament winding machine which is also developed at Nottingham University. The results show a considerable improvement in the winding speed and the accuracy of fiber placement.     

Generating realistic laminate fiber angle distributions for optimal variable stiffness laminates

The advent of advanced fiber placement technology has made it possible, through the use of fiber steering, to exploit the anisotropic properties of composite materials to a larger extent than was previously possible. Spatial variation of stiffness can be induced by steering composite fibers in curvilinear paths to give beneficial load and stiffness distribution patterns. Buckling of composite panels is one area where fiber steering has been proven to be very effective. Fiber angles and predefined fiber angle variations are used in most of the research on fiber steered composites reported in the literature, however, from an optimization point of view it is attractive to design such variable stiffness (VS) structures in terms of lamination parameters (LPs). This results in a two-step design approach. In the first step a VS composite is designed in terms of LPs, and in the second step the LPs are converted into fiber angle distributions for each layer in the laminate. A methodology is proposed to convert a known LP distribution for a VS composite laminate into a realistic design in terms of fiber angles, with minimum loss of structural performance, whilst satisfying a constraint on in-plane fiber angle curvature. The proposed conversion process is formulated as an optimization problem and can be used for any number of equi-thickness plies. The methodology was tested by converting a known optimal LP design for a sample structure, a square plate under bi-axial compression into a fiber angle design. The effect of the in-plane curvature constraint, the number of layers in the laminate, and the choice of objective function for the conversion process were studied for a balanced symmetric lay-up.     

WHIPOX®: Ein faserverstärkter oxidkeramischer Werkstoff für Hochtemperatur– Langzeitanwendungen

WHIPOX®: A fiber‐reinforced oxide‐ceramic matrix composite for long‐term high‐temperature applications In the last years the all oxide fiber reinforced ceramic matrix composite WHIPOX® ( W ound Hi ghly P orous Ox ide CMC) have been developed to fabricate mature components. Besides the applications in the field of aircraft and space technology, which are developed in interdisciplinary projects at DLR, the material was successfully tested for “spin‐off” applications. The specific and unique combination of physical and mechanical properties enables new and innovative solutions for problems with materials in industrial furnaces, metallurgical equipments, filter technologies, fire prevention, catalytic converters, soot filters, electro technology and medical applications. High speed burner injectors for industrial furnaces are produced in licence by an industrial ceramic manufacturer.     

Asymmetric hybrid composite: A design concept to improve flexural properties of Kevlar Aramid composites

Asymmetric hybridization is proposed as a mechnanism for improvement of flexural properties of composites reinforced with Kevlar¹ aramid fiber, where the compressive strength of the fiber is a limiting factor. A calculation based on a bi-material beam model is presented, which determines the placement and arrangement of fibers in a composite such that the stress developed on the tensile side of the composite equals the ultimate tensile strength of Kevlar. An experimental investigation was conducted with asymmetric hybrid composites of J-polymer reinforced with Kevlar and carbon fibers. In the best cases, the observed ultimate flexural and shear strengths were improved by 40% and 25% by comparison with values typically seen for composites of J-polymer and Kevlar.     

Machinablity of Hybrid Natural Fiber Composite with and without Filler as Reinforcement

The filler materials are reinforced along with natural fibers in the composite to improve the quality and property of the component materials based on the requirements and its applications. In this paper, hybrid natural fiber composites were developed with and without filler materials as reinforcement. The developed hybrid natural fiber composites are machined using abrasive water jet cutting process with three different cutting parameters. The influences of cutting parameters are evaluated with respect to the kerf wall inclination, material removal rate, and surface roughness. The surface morphology was also studied to infer the basic mechanism involved during composite machining. The hybrid fiber composite with filler has proved that it can produce good engineering component without delamination and fiber pullouts during machining.