Improving the stiffness of multilayer 3D woven composites by the integration of shape memory alloys (SMAs) into structures

Abstract

Shape memory alloys (SMAs) are capable of shape-retaining and stress generation when activated. SMA wires are embedded in laminated composites for improving the properties of the composites. Laminated composites have low through-the-thickness properties and poor delamination resistance. 3D composites are well known for having higher through-the-thickness properties. In 3D woven composites, a set of yarn is in through-the-thickness direction that improves through-the- thickness properties and provides resistance to delamination of layers. As in multilayer 3D woven structures, yarns are distributed from in-plane to through-the-thickness direction, so in-plane properties are reduced with the same number of yarns compared to 2D laminated composites. In this research, SMA wires are embedded into different types of 3D woven structures for utilising stress generation property of SMA wires for improving in-plane properties, specifically stiffness of the composites. Three types of 3D orthogonal interlocking composites: layer-to-layer, through-the-thickness, and modified multilayer interlock structures are fabricated with and without SMA wires. From the tensile test, results show that embedding SMA wires into structures significantly improves the stiffness of the structures due to the stress-induced martensite phase of SMA wire when subjected to load. When these SMA wires are activated, stresses are generated by SMA wires due to phase transformation from martensite to austenite that further gives remarkable higher values of stiffness. This results in a composite structure that has higher in-plane properties due to embedded SMA wire and through-the-thickness properties due to 3D structure of composite reinforcement. The interlocking pattern in the through-the-thickness direction of 3D structures was also found to have an effect on the extent of the improvement in stiffness.     

三维正交机织复合材料的冲后压缩性能

为揭示纱线张力对三维机织复合材料抗冲击及冲后压缩性能的影响规律,基于多剑杆织造工艺,配置不同接结纱张力(25、50、100 cN)织造三维正交机织物,通过真空辅助树脂传递模塑成型工艺制备复合材料,并在室温下进行低速冲击及冲后压缩性能测试。结果表明：当接结纱张力为100 cN时,试样在冲击载荷下发生表层树脂大面积破裂和剥离并使纬纱失去支撑,同时,试样表层纬纱发生较大卷曲,促使压缩载荷发生屈曲失效;接结纱张力为100 cN试样的压缩性能相比接结纱张力为25 cN试样下降约50%;接结纱张力较高时易导致纬纱卷曲增大和树脂富集,并由此降低试样的弯曲刚度和冲后压缩性能。     

Investigation of mechanical behavior of woven/knitted hybrid composites

The objective of this research is to develop the woven/knitted hybrid composites for improved in plane as well as out of plane mechanical properties. Two different type of structures and two different materials were used in this study. Firstly, the woven and knitted fabrics were developed with glass and Kevlar yarn. Secondly, the laminated composite samples were fabricated with different stacking sequence of fabric plies. The epoxy resin was used as matrix. The cured samples were characterized for impact, tensile and dynamic mechanical properties. The behavior of composite materials was then analyzed with percentages of different fiber and fabric types. The samples with higher percentages of knitted reinforcement gave better impact strength but failed to provide better tensile properties. Moreover, the samples with higher percentages of woven structure and glass materials gives better modulus values.     

冲击波在陶瓷增强纬编双轴向多层衬纱织物及机织物复合材料中传递的表征

为了分析冲击波在复合材料内的传递规律,通过将纬编双轴向(MBWK)多层衬纱织物、机织物与陶瓷层交替铺层与不饱和聚酯树脂进行复合制备了复合材料,利用落锤冲击试验机对复合材料进行冲击测试,研究了试样冲击破坏后陶瓷片裂纹扩展及碎裂规律,探讨了冲击应力在不同结构复合材料内部的传播规律,并分析了MBWK织物增强复合材料的冲击应力波传播机制。结果表明:复合材料在冲击过程中,出现了材料的分层损伤;冲击应力波横波表现在陶瓷材料表面,即造成陶瓷材料环形损伤;冲击应力波纵波沿材料厚度方向传播,复合材料各层对能量的吸收有差别;同时,相同工艺条件下,机织物复合材料破坏面积小、裂纹数量少,说明机织物复合材料对冲击能量吸收较多、抗冲击性能较好。     

Modelling the geometry of the unit cell of woven fabrics with integrated stiffener sections

Composite-stiffened panels of naval and aerospace applications are under the risk of delamination due to the lack of reinforcement at the joints of panel and stiffener section. One of the sustainable remedy to overcome such problems is to use 3D woven performs as a reinforcement. The benefit of 3D weaving is its intricate weave architecture and its ability to create near net shaped preforms for structural reinforcements. The technique provides endless permutations and combinations for weave design, however, repeat unit cell is the common factor that represents the complete weave architecture of the fabric. The behavior of the unit cell represents the behavior of the composite as a whole. The work presented in this paper details on the geometrical representation of an unit cell of woven stiffener fabrics and formulation of a modeling approach to determine its total weight and Fiber Volume Fraction. In this work, woven fabrics with integrated stiffener sections of four different configurations were produced using modified face-to-face (terry) weaving principle and their geometrical parameters were formulated through the modeling approach. The computed results from the models show close approximation with experimental values thus justifying the prediction of performance through them.     

纬纱接结的三维正交机织物结构

为了研究正交机织物的实际结构,采用玻璃纤维在剑杆织机上织制了纬纱接结的6层经纱5层纬纱的正交机织物,然后利用VARI工艺与聚酯树脂复合,制成了复合材料板材试样,并在显微镜下观测纱线的形状。研究发现:三维正交机织物的经、纬纱基本呈直线状态,接结纬纱是曲线与直线组合的形状,且形状与在织物中的位置有关,越靠近织物中央,接结纬纱的直线部分越短;接结纬纱使其限定的经纱产生聚集现象,在复合材料中产生贫富树脂区,接结纬纱形状的变化也使织物的结构不均匀。对织造过程的分析表明,造成接结纬纱形状变化的原因是织物形成过程中接结纬纱的滑动,从织物边部到中央,接结纬纱的滑动阻力逐渐增大,接结纬纱的张力也逐渐增大。     

组合式三维机织复合材料的制备及其抗高速冲击性能

为研发轻质柔软的高效防护装备,以超高分子量聚乙烯（UHMWPE)纤维为原料,以正交与准正交结构单元为基础,设计了8种组合式的三维机织结构,试制UHMWPE组合式机织复合材料。研究采用弹道侵彻试验及刚柔性试验测试了复合材料的抗高速冲击性能及柔软性,探讨了影响材料防弹性能及服用性能的主要因素。研究表明：正交结构单元能够有效抵抗剪切作用,适合作为冲击面。在高速冲击下,冲击面为正交结构单元的机织复合材料单位面积吸收能量值比冲击面为准正交结构单元的机织复合材料高出了35.7 %;但准正交结构单元对于抗拉伸作用具有优势,且准正交结构织物抗弯刚度值仅为组合式结构织物最大值的52 %,具有较好的柔软性。     

A review on the mechanical performance and fatigue behavior of 3-D angle-interlock woven composites

The 3-D textile structural composites (3DTSC) have attracted the special attention because of their excellent structural stability, higher fracture tolerance, and delamination resistance capability owing to the existence of fibers along the thickness direction. As one type of the 3DTSC, the 3-D angle-interlock woven composite (3DAWC) has attracted increasing attention in structural engineering applications owing to its special mechanical performance. In this review, the research progress on the mechanical performance of the 3DAWC undergoing the tension, compression, and impact loading conditions has been summarized. Furthermore, the research development on the fatigue behavior of the 2-D textile structural composites and the 3DTSC, as well as the comparisons of the fatigue-resistance performance between the different types of textile structural composites have been introduced. In addition, the progress, key issues, and future trend on the fatigue damage behavior of the 3DAWC are also given in this review.     

Investigating the effect of material and weave design on comfort properties of bilayer-woven fabrics

The paper focuses on the development of a bilayer-woven fabric and investigating the effect of weave design and material type on its comfort properties. Face layer was plain woven with cotton yarn, while two different weave designs (2/2 and 3/1 twill) and four different materials (cotton, polyester, micropolyester and nylon) were used for the back layer. The comfort properties of fabric, including air permeability (AP), thermal resistance, water vapour resistance and overall moisture management capacity, were determined. It was found that both the layers of fabric as a whole contribute to the comfort properties of bilayer fabric. The highest AP was exhibited by fabrics having both layers of cotton, while 3/1 twill samples have a lower value of thermal resistance as compared to the 2/2 twill samples. The results further showed that micro polyester woven in 3/1 twill weave exhibits better comfort properties.     

基于气缸的三维机织增强体织造系统设计

为在经纱方向引入贯穿织物厚度的接结纱从而提升机织增强复合材料层间性能,以三维正交无卷曲机织增强体为对象,设计了一种窄幅三维机织织造系统。采用气缸作为开口、引纬和打纬的主要驱动部件,实现多重综框的独立开口运动与管状多剑杆机构的多层梭口同时引纬运动,并在可编程控制器上实现各机构协调运作,使经纬纱垂直平铺,接结纱与纬纱交织并贯穿织物起到层间约束作用。通过显微镜观察三维机织增强复合材料各个切面(分别沿经纱、纬纱和接结纱),并测量纱线卷曲度、横截面积、组织单元尺寸等关键几何参数。测量结果表明,这种三维机织系统可实现三维正交无卷曲机织增强体的织造。     

芯材结构对纤维增强复合材料抗压性能影响的有限元分析

为了说明芯材结构对中空纤维增强复合材料力学行为的影响,通过有限元分析的方法,在纱线芯材、树脂尺度上计算并比较“π”形与“O”形这两种不同芯材结构纤维增强复合材料在相同压力作用下的动态响应。通过对比分析两种材料结构的挠度随时间的变化、应力在结构中的分布、最大、最小应力所在位置以及应力均衡度等发现：复合材料（“O”形芯材）的变形程度比复合材料（“π”形芯材）的变形程度小。此外,对于前者而言,其应力集中部位处于几何结构对称的中心线上,这种对称性对材料结构的整体承力有利,且应力的不均衡度较小,使其能够吸收与耗散较多的能量。     

Mechanical Response of Novel 3D Woven Flax Composites with Variation in Z Yarn Binding

ABSTRACT

This paper is focused on the development of novel 3D woven flax composites for improved mechanical performance. The 3D woven interlock fabrics were produced on dobby loom using novel weaving patterns, with variation in binding point density (four different levels). These fabric structures were then used to fabricate composites with green epoxy resin as a matrix. Tensile, flexural, short beam shear, impact (pendulum and drop weight) and compression after impact properties were characterized. It was found that 3D woven composites having higher binding point density showed overall improved mechanical behavior, i.e. the out-of-plane properties were enhanced whereas in-plane properties are either reduced or unaffected.     

不同结构厚截面三维机织碳纤维复合材料的弯曲性能对比

为准确分析不同结构厚截面复合材料不同方向上的弯曲性能差异,通过设计织造三向正交、浅交直联、浅交弯联3种典型机织结构的厚截面碳纤维三维机织物,并采用真空辅助树脂成型工艺制备了近似纤维体积含量的碳纤维复合材料板,对其进行了XYZ方向的弯曲实验。结果表明:三向正交结构由于内部纤维束近似平直,碳纤维束自身性能得到最大利用,对应复合材料经向弯曲强度最好;浅交直联结构复合材料的Z经和Z纬弯曲强度累加值最大,其厚度截面上的综合弯曲性能最好,且其他各方向的弯曲强度较为均衡;浅交弯联结构内部纱线交织摩擦损伤严重,且经纱屈曲程度最大,对应复合材料经纬向弯曲性能均为最差。     

三维机织复合材料板簧式起落架结构设计及其有限元分析

为实现直升机板簧式起落架减重和提高层间剪切性能,采用碳纤维三维机织结构整体制备复合材料起落架。针对起落架的设计要求,通过受力分析和理论计算,建立了板簧式起落架的三维力学分析模型;通过材料实验和理论计算,获得了有限元计算所需的材料工程常数;结合最大应力-应变准则,采用有限元方法对板簧进行准静态加载模拟,确定了板簧的截面和轴线几何形状,以及变截面增厚部位的长度值与厚度值。结果表明:基于斜纹2.5维机织复合材料结构,截面宽度为120 mm,厚度为24 mm的弓式圆弧形、矩形截面板簧在满足挠度的同时其应变小于材料许用应变值;基于优选截面,增厚长度为760 mm,增厚厚度为36 mm时,复合材料起落架不仅能较好满足挠度、强度等设计要求,而且在同类型航空用4340钢制成的板簧结构件基础上质量减少约30%。     

基于一元二次函数的层联机织预制体细观结构表征

织物预制体结构参数之间的相互关系是高性能复合材料设计需要解决的关键问题。为建立层联机织预制体的细观几何关系,通过显微观察和结构分析提出基于一元二次函数的抛物线凸透镜形纬纱横截面、抛物线形经纱路径等假设,通过研究典型的多层平纹层间联锁结构层联机织预制体,建立预制体全厚度单胞模型,推导其细观结构参数的几何表达,获得纱线横截面变异系数、预制体厚度和纤维体积含量的计算方法,从而实现预制体结构的细观设计。通过实测值和理论预测值的对比,验证了该细观模型的有效性和合理性,并确定了层联机织平纹预制体的纱线填充因子取值区间为0.73~0.87。     

单向复合材料及纯树脂材料抗冲击性能的比较

运用有限元软件ABAQUS,在纱线与树脂基体尺度上计算单向复合材料的抗冲击过程。通过对比分析相同条件下纯树脂材料的抗冲击能力,从弹体的速度变化曲线、冲击应力在复合材料不同组分上的分布等方面说明单向复合材料的抗冲击行为与主要吸能机制。在冲击作用下,与纯树脂材料相比,单向复合材料可使冲击能量在较短的时间内得以耗散,从而表现出更好的能量吸收性能。此外,单向复合材料中的纱线部分的应力峰值明显比树脂部分的应力峰值大,说明单向复合材料所承受的冲击能量主要被纱线增强相所吸收,从而具有更好的抵抗冲击的能力。     

Flexural stability analysis of composite panels reinforced with stiffener integral woven preforms

3D weaving exhibits to be a guaranteeing innovation in delivering integrated near net shaped structures that might overcome the current issue of delamination and assembly cost. This paper highlights one such technique of producing preforms with integrally woven stiffener sections that can be used as a reinforcement material for composite panels. The woven performs were fabricated using high performance polyester yarns as a raw material and further consolidated to composite structures using epoxy resin. The flexural analysis of the composite panels developed from these performs revealed that the structures have better bending rigidity and structural integrity without any possibility of delamination prone failures. Investigations on fracture morphology were conducted to understand the composite failure mechanism and the structural deformation of the structures during loading. From the findings, it was evident that the polyester-epoxy material combination exhibited substantial residual strength and toughness properties.     

Study of changes in 3D-woven multilayer interlock fabric preforms while forming

Multilayer woven reinforcements are increasingly employed in the domain of composite materials. Delamination occurrence and resultant failure of a laminated composite piece subjected to high vibrations, is an issue of much concern in aeronautics. The situation becomes more complex in case of bended/curved pieces. In order to improve through the thickness mechanical properties, 3D-woven multilayer interlock fabric is used as composite reinforcement. Structural changes, i.e. thickness change, relative slippage of layers, change in tow aspect ratio and change of orientation of the tows columns, etc. occur in such fabrics during the forming process. These changes may lead to the gradient of the resin amount in composite, internal stresses and variations of mechanical properties in the piece. No significant research has been conducted on this aspect. Lack of knowledge or neglecting these changes may lead to prejudicial estimations of ultimate mechanical properties and fracture analysis. In the present article, the changes that occurred in 5-layer and 13-layer 3D-woven multilayer interlock fabrics have been studied, when moulded at five different angles and two different bending radii. A significant change in thickness, tow aspect ratio, tow orientation and relative layer slippage is observed.     

柔性个体防护材料抗穿刺性能的试验研究

以防刺材料的测试标准介绍测试仪器、试验参数及样品结构选择,分析柔性防刺服的防刺机理和性能。结果表明,一定范围内增加材料厚度是提高柔性防刺服防刺性能的有效途径;混合结构的柔性复合防刺服能达到较为理想的防刺效果。试验中验证的这类复合结构包括纬编轴向衬纱(MBWK)织物与纬平针织物混合制作而成的防刺织物;单一结构织物复合材料的防刺性能比复合结构材料的差。     

三维正交机织物织造及复合材料成型工艺研究

详细阐述三维正交机织物的结构特征、织造原理及织造工艺,以三维正交机织物为增强体、环氧树脂为基体,采用真空辅助树脂传递模塑(VARTM)工艺成型,制成复合材料,并分析其内部结构。结果表明:由普通织机改造的多综眼多剑杆织机可以织造三维正交机织物,成型后复合材料内的纱线形状和位置未发生明显变化,树脂较好地渗透到织物内部,复合材料具有较高的纤维体积分数。研究结果为进一步研究三维正交机织复合材料的力学性能及应用奠定了基础。