三维机织预型件的织造技术

纺织复合材料预型件的生产工艺有多种,其生产路径主要由最终用途决定。三维机织物是通过对传统织造原理改进加工而成的。二维机织复合材料是一种由二维织物构成的层合材料,而三维机织复合材料是复杂几何结构的整体构件。三维机织复合材料预型件有许多优点,最重要的优点是它避免了二维层合材料的分层现象。介绍了三维机织预型件的织造方法,为纺织复合材料的开发提供了有益的借鉴。     

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。     

二维与三维机织复合材料力学性能的实验研究

对超厚三维正交机织复合材料及二维要织层合板人别进行了拉伸和压缩实验,研究比较了两种复合材料刚度和强度特性的差异研究发现无论是三维机织材料的拉压还是二维层合板的拉压应力应变曲线都近似为直线,而且具有脆性破坏的特点;三维复合材料的拉压强度要高于二维层合板.这主要是由于材料不同的增强相结构及纤维含量造成;不同的破坏模式对材料强度影响很大.     

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.     

聚氯乙烯膜结构复合材料的光氧老化行为及评价

为探究经编和机织涂层膜结构复合材料的光氧老化行为,以涤纶经编和机织聚氯乙烯(PVC)涂层膜结构复合材料为对象,选取6种织物试样,研究其在紫外光辐射下的老化现象,同时与涤纶纱线力学性能的老化效应进行对比;同时研究了老化实验过程中复合材料的光氧老化行为及力学性能变化,并分析了其微观损伤机制。结果表明:涂层膜对基布纱线起到了很好的保护作用;经编织物膜结构材料老化后的初始模量均高于机织物膜结构材料,断裂强力保持率则反之;在辐射能为82.08×10³ kJ/m²时,织物的横密和纵密均为24根/(5 cm)的单面经编膜结构复合材料断裂强力保持率仅为62.4%,且其涂层对基布的保护作用已失效,涂层膜表面严重粉化和黏结;另外5种双面膜结构试样断裂强力保持率均在85%以上,在此辐射能范围内涂层面变粗糙,但仅出现少量沟槽,表现出良好的抗光氧老化性能。     

立体织物在二氧化硅基复合材料方面的应用前景

摘要：连续纤维及其织物增韧的二氧化硅基（SiO2）复合材料具有强度高、韧性好、密度低等特点,是用于天线罩的理想材料。本文从不同增韧方式的成型工艺方法、增韧特点出发,综合评价了用于天线罩的颗粒增韧、晶须增韧和连续纤维增韧二氧化硅基复合材料的研究现状,提出适合于增韧二氧化硅基复合材料的立体织物纤维束结构,其中典型的纤维束交织结构包括2.5D机织、正交三向、三维编织及其衍生结构。最后,结合未来导弹天线罩材料的发展趋势,指出了立体织物在二氧化硅基复合材料方面的广泛应用前景和研究重点。     

Investigating the mechanical behavior of composites made from textile industry waste

Recycling the waste for environmental protection has been an important challenge for the mankind. The fibrous waste in textile industry accounts for approximately 15% of the amount of fibers used, leading to a lower yield %. The current study focused to use this waste as reinforcement to produce a fiber-reinforced polymer composites. Reinforcements were woven in 3/1 S twill, using yarn produced from noil waste and knitting waste in the weft direction. The weft yarn count, type of waste material and number of picks were the variables of study. Laminated composites were fabricated from these reinforcements and the mechanical properties (tensile, bending and impact) were compared to the conventional glass fiber composites. The specific mechanical properties of these composites were found comparable or less than that of glass fiber composites.     

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.     

玻璃纤维多轴向经编复合材料的制备及拉伸性能研究

以环氧树脂为基体,分别以玻璃纤维多轴向经编针织物和玻璃纤维机织物作为增强材料,通过手糊法制备复合材料,并通过试验对比研究两种复合材料的拉伸性能。结果表明,经编复合材料沿各个轴向的拉伸强度比复合前多轴向经编针织物及机织复合材料的强度均有明显提高,增幅均在50%以上,说明多轴向经编复合材料具有更优异的力学性能。这为进一步扩大玻璃纤维多轴向经编复合材料的应用领域提供了有力证据。     

Development of composite materials reinforced with flat-knitted spacer fabrics

Flat-knitting technology has recently known spectacular developments with the advent of 3D spacer fabrics used as reinforcements of sandwich composites thanks to their improved mechanical properties. At present, studies dealing with the development and the characterization of these composites are quite rare .This work deals with the development of 3D-knitted composite using cotton yarn and unsaturated polyester resin. The aim of this work is to evaluate the utility of a natural reinforcement material in a technical use and assess the impact of fabric cross-link shape on composite mechanical performances. U- and V-shaped 3D spacer fabrics were produced and used to develop composite structures. These structures were characterized by flexion and flat compression tests. Results showed that composites reinforced with U spacer fabric have the best compression resistance whereas the best flexural properties were obtained with V-shaped fabric connection. The developed structures present competitive solution for light weight composites such as solar panels, blades of wind turbines, and sound absorbers.     

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。     

A generalized analytical model for predicting the tensile behavior of 3D orthogonal woven composites using finite deformation approach

Over the past few decades, there have been an increasing interest in woven preforms as a reinforcement for composites. The invention of 3D Orthogonal Weaving (3DOW) technology introduced new and enhanced features to the conventional 2D woven preforms. Modeling the tensile behavior of 3DOW composites is very useful to the industry, it helps in characterizing the composite material with minimal need for coupon testing. In this study, a generalized analytical model was developed to predict the entire load–extension curve of the 3DOW preforms and composites including the non-linear region, using the finite-deformation approach. The model relies on the geometry of the structure and the tensile properties of the constituent yarn and resin components as input parameters. The model was generalized to predict the properties of any 3DOW structure, made with spun or filament yarn, jammed and non-jammed, which have any weave architecture, including hybrid composites. The model was verified experimentally for a broad range of experimental composites, including hybrid ones. The results indicated that there was a general good agreement between the experimental and theoretical curves.     

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。     

Sheet forming of woven fabric composite by combined cyclic stretch and deep drawing

The manufacturing of composites often requires transformation of 2-D fabrics into various structural 3-D shapes through preform processing without over straining of the yarns or wrinkling. Sheet forming of woven fabric composite by combined cyclic stretch and deep drawing was suggested. In order to prevent the wrinkling, the geometrical and mechanical properties of fabric should be chosen to get the final form of the prepregs beforehand. Geometrical investigation of the final bagged form dimensions are based on geometrical aspects of the wrapping of the fabric. In this study, an approach was proposed to form the reinforcement fabric composite through the dynamic bagging of the fabric by the application of cyclic stretching on the fabric during formation of 3-D reinforcement structure in hot environment. The dimensions of the flat fabric were calculated and the parameters of the forming process analyzed in two cases: hemisphere and flat top cone shape.     

2.5D角联锁织物厚向压缩特性的实验研究

以碳纤维2.5D衬经结构织物为例,初步研究了2.5D角联锁织物厚度方向压缩特性,利用万能材料试验机测得织物厚度与压缩应力的关系。研究发现,当压缩应力小于3 MPa时,经验指数取为3的多层平纹织物压缩模型可用于2.5D衬经织物厚度与压缩应力关系估算。在4种不同压缩应力下制备2.5D衬经结构复合材料,进一步观测经向和纬向截面内经纱、衬经纱和纬纱屈曲变化情况,引用纱线段局部屈曲角分布定量表征纱线的屈曲程度。结果发现:经纱的屈曲程度最高,随压缩应力的增加,经纱的屈曲程度降低;当压缩应力超过一定范围时,经纱屈曲程度反而增加,衬经纱和纬纱基本呈伸直状态,衬经纱屈曲程度增加,纬纱伸直度增加。     

层-层正交角联锁机织物及其复合材料的结构及其层切破坏机制研究

采用无损高分辨率X射线成像(显微X-CT)技术对层-层正交角联锁机织物以及复合材料内部结构进行分析,并研究了层间剪切强度与结构之间的关系;通过三维重构展现了机织物的层-层正交角联锁的微观结构,观察到机织物内部的单丝扭转、挤压现象;依据机织复合材料中孔隙和高密度杂质在三维空间的分布,计算了其相应的占比。结果表明:层间剪切实验后的机织复合材料虽然宏观形貌保持了良好的完整性,但内部存在孔隙变形、分层、纤维弯曲、片层断裂等现象;层-层正交角联锁机织结构有效提高了复合材料的层间力学性能,内部的缺陷对复合材料的力学性能有较大的影响;无损高分辨X射线成像技术是研究纤维增强复合材料内部复杂结构特性的有利手段。     

三维机织热塑复合材料的弯曲性能测试与分析

对三维机织热塑复合材料的弯曲性能进行了测试和分析。研究结果表明,三维机织热塑复合材料预型件的结构(纱线的直径、三维机织物的结构)、预型件的预拉伸工艺(经纱和接结经的伸直程度)、复合成型工艺(成型压力)都对复合材料的弯曲性能有一定的影响。     

机织物外观计算机模拟方法的探讨

评述了织物ＣＡＤ系统中机织物外观计算机模拟现状,指出了其存在的问题,提出建立在纱线实体模型基础上的织物外观三维计算机模拟方法,该方法不仅可以模拟织物结构参数变化时织物外观的变化,还为实现复杂组织结构的可视化奠定了基础。     

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。