基于SPH方法的鸟撞复合材料层合板数值分析

采用光滑粒子流体动力学法(SPH)耦合有限元法对复合材料层合板受鸟撞击的过程进行了数值模拟。复合材料层合板采用渐进损伤模型,鸟体采用SPH粒子建立模型,利用ANSYS/LS-DYNA显示动力分析模块分析了复合材料层合板结构非线性接触。分析了鸟撞层合板过程中鸟体损伤及层合板单层纤维失效和基体失效情况,分析了鸟体的入射角方向及层合板采用不同铺层时对层合板吸能效果的影响。计算结果表明,合理设计层合板铺层可以提高层合板的吸能效果。     

纤维曲线铺放制备变刚度复合材料层合板的研究进展

纤维曲线铺放技术可以同时对刚度和强度进行剪裁优化设计,由此制得的变刚度复合材料层合板与传统的复合材料层合板相比,其重量和成本可以减少10%～30%,同时结构性能得到显著提高。本文先介绍了纤维曲线铺放技术及变刚度复合材料的概念,对比分析了纤维曲线铺放的两种方法,然后讨论了变刚度复合材料层合板设计制造的主要问题,重点论述了纤维曲线铺放变刚度层合板的应用研究,最后对纤维曲线铺放技术的应用前景进行了展望。     

复合材料层合板孔边应力场的有限元计算

纤维增强复合材料具有较高的比强度、比刚度和比模量,在航空航天领域得到越来越广泛的应用.层合板是当前复合材料在工程结构中应用的主要形式.对于含孔的层合板结构,由于材料的各向异性以及孔的影响,其应力分布比较复杂,采用数值解是较好的选择.本文基于层合板的可设计性特点,综合考虑铺层角度、铺层顺序等对层合结构的影响,设计出了一种二十四层对称层合板.以有限元方法为基础,借助ANSYS分析工具,对该层合板含孔结构的孔边应力重点分析,得出了不同铺层角度铺层中应力分布的云图和孔边应力分布曲线.本文结论对复合材料层合板优化设计和带孔层合结构的应力计算具有较好的参考价值.     

汽车复合材料层合板准静态力学性能的试验测定

以应用于某新能源电动汽车的复合材料层合板为研究对象,利用万能试验机和静态应变测试分析系统等提出了可靠的复合材料层合板准静态拉伸和压缩力学性能试验测定方法,从而为复合材料结构在汽车轻量化中的设计和应用提供了试验依据。该层合板结构采用±45°交叉铺层方法,由2层碳纤维、1层芳纶纤维和2层玻璃纤维层叠构成。试验结果表明,该复合材料层合板在准静态拉伸时呈现沿±45°方向和层间分离挤压的断裂失效模式,这与其内部纤维铺层方向是一致的。同时,由于在复合材料板材中加入了增韧和板材失效时起连接作用的芳纶纤维和玻璃纤维铺层,该复合材料层合板的整体力学性能较常见碳纤维增强复合材料板材,其弹性模量和强度性能均有所降低。     

复合材料层合板强度界限

本文提出了复合材料层合板强度上下限的概念，给出了层合板强度上下限的计算方法，并以复合材料单向板的强度准则的为基础，对一些特殊铺层的层合板在几种受力状态下的强度限进行了讨论。     

某型无人机机翼复合材料大梁迭代设计方法与有限元强度验证

根据工字梁腹板及缘条受力特点,计算了某型无人机机翼大梁在均布升力作用下腹板和缘条的内力。基于经典层合板理论和最大应力强度准则,采用Matlab软件编程,运用迭代法设计了机翼工字形层合结构大梁的铺层结构。建立了复合材料层合结构大梁的有限元模型,基于最大应力强度准则对大梁结构进行有限元强度校核,给出了各层的安全裕度。分析结果表明,基于经典层合板理论的迭代设计方法能够在有限次迭代后设计出符合要求的复合材料层合结构翼梁,层合结构翼梁各铺层安全裕度均大于0.5,该工字梁结构强度符合设计要求。     

板锥网壳结构复合材料层合板的屈曲分析

板锥网壳结构是一种受力性能合理,技术经济效益良好的新型空间结构形式.本文结合复合材料力学理论和复合材料结构力学(板壳理论),采用组合结构有限元对复合材料层合板自身的局部稳定性和主要影响因素进行全面和深入的研究,研究复合材料板锥网壳结构的受力性能,为复合材料板锥网壳结构设计和层合板铺层设计提供理论上的依据,得出了可应用于工程实践的重要结论.     

板锥网壳结构复合材料层合板的强度分析

板锥网壳结构是一种受力性能合理、技术经济效益良好的新型空间结构形式.本文结合复合材料力学理论和复合材料结构力学(板壳理论),采用组合结构有限元对复合材料层合板自身的强度和主要影响因素进行全面和深入的研究,研究复合材料板锥网壳结构的受力性能,为复合材料板锥网壳结构设计和层合板铺层设计提供理论上的依据,得出了可应用于工程实践的重要结论.     

FRP层合板低速冲击损伤特性研究现状与展望

纤维增强复合材料层合板(FRP)由于具有比强度高、比模量高、可设计性强等特性,在工程领域得到越来越广泛的应用。但是低速冲击造成的损伤对层合板力学性能的影响非常显著,导致其强度和刚度下降。本文针对近年来纤维增强复合材料层合板低速冲击作用下的损伤研究进行了综述和回顾,重点介绍了试验研究方法、模拟计算研究方法、FRP层合板损伤性能表征方法,并对有待于进一步研究的问题进行了展望。     

铺层结构对复合材料层合板弯曲强度及失效行为的影响

通过改变偏轴角为45°和90°的[45°/–45°],[0°/90°]正交铺层组的质量分数,设计了6种复合材料层合板铺层结构。研究了两种偏轴角正交铺层组共同存在的铺层结构对真空辅助树脂传递模塑工艺复合材料层合板弯曲强度及失效行为的影响。通过弯曲实验获得6种复合材料层合板的弯曲强度、损伤特征以及应力–应变曲线。结果表明,随偏轴角为90°的[0°/90°]铺层组质量分数的增加,复合材料层合板的弯曲强度逐渐增大;两种偏轴角正交铺层组共同存在的铺层结构可引起复合材料层合板在弯曲载荷作用下的损伤模式多元化。     

Vliesstoffe der zweiten generation

Second generation non wovens are demonstrated by three examples: Artificial leather with a structure similar to natural leather, non woven without any chemical binders bonded by fibre entanglement, non woven with textile properties bonded by bonding fibers. It is shown which ways can be gone to get known structures by new processes, and to open the non wovens new fields.     

Colour change as a result of textile transformations

This paper studies the influence of textile structure on its colour. It provides a systematic analysis of the changes in spectral reflectance and hence colour differences between three textile substrates: roving, yarn and woven fabric. The transformations of the reflectance spectrum as a result of the changes of the structure were modelled and the evolutions of the colorimetric coordinates L *, a *, b *, C * and h associated with these various transformations were thus calculated and analysed. The work also offers a useful method of modelling the predicted colour from one substrate form to another, which is important to the textile industry.     

摩擦纺包缠纱纺织预型件及其复合材料的加工

本文研究了摩擦纺包缠纱纺织预型件及其复合材料的加工性能。借助地机织，纺织和针织等三种预型件加工方法，通过必种典型纺织结构的加工研究了摩擦纺包缠纱的预型件加工性能，并在平板热压机上成型了几种结构的复合材料，结果表明：摩擦纺包弹纱可以用于纺织预型件加工以成型纺织结构型的复合材料，灵活地运用纺织结构可以得到独特结构的复合材料，此外摩擦纺包缠纱经适当防剥离处理后，可加工出紧密结构机织物，以成型较高纤维体积     

机织/针织混合铺层对复合材料力学性能的影响

为使纺织复合材料同时具有机织结构复合材料和针织结构复合材料的综合力学性能,通过混合铺层方式制备机织/针织混合结构复合材料。以芳纶机织平纹织物和针织罗纹织物为增强体,以环氧树脂为基体,调整复合材料中增强体的铺层顺序,利用真空辅助成型技术制备四层层压机织/针织混合结构复合材料。通过对复合材料拉伸性能、弯曲性能和冲击性能的测试,分析混合铺层和铺层顺序对芳纶环氧树脂复合材料力学性能的影响。结果表明,混合铺层和铺层顺序对芳纶环氧树脂复合材料的弯曲强度和冲击强度有较大影响,特别是对罗纹结构复合材料纬向弯曲强度和冲击强度的改善。当采用相同铺层方式,罗纹织物为受力面时,机织/针织混合结构复合材料具有较大弯曲强度和冲击强度。     

Atmospheric air-plasma treatments of polyester textile structures

The effects of atmospheric air-plasma treatments on woven and non-woven polyester (PET) textile structures were studied by surface analysis methods: wettability and capillarity methods, as well as atomic force microscopy/lateral force microscopy (AFM/LFM). The water contact angle on plasma-treated PET decreased from 80° to 50–40°, indicating an increase in the surface energy of PET fibres due to a change in the fiber surface chemical nature, which was confirmed by a higher fiber friction force measured by the LFM. The extent of water contact angle decrease, as well as the wash fastness of the treatment varied with the structure of the textile. Indeed the more porous the textile structure is (such as a non-woven), the fewer are the chain scissions of the PET at the fiber surface, during the plasma treatment. Thus, the level of surface oxidation and the weak boundary layers formation depend not only on plasma treatment parameters but also on the textile structure.     

Review of the Mechanical Properties of a 3D Woven Composite and Its Applications

Owing to their complex structural characteristics, 3D woven composites display different mechanical properties and failure modes from traditional composite laminates. The relations between the weaving geometry and main mechanical properties of composites are obtained by studying the internal structures of 3D woven textile. This paper reviews the research on the mechanical behavior such as tension, compression, shear, flexural, and impact properties, and analytical models of 3D woven polymer matrix composites mainly in four major inner structures and discusses the development of mechanical properties and applications of 3D woven fabrics and suggests further studies on aero industry.     

A simplified in‐plane permeability model for textile fabrics

In this paper, a simplified in‐plane permeability model for textile fabrics is developed. The model is based on a rectangular unit cell geometry, the one‐dimensional Stokes equation for flow in the channels or gaps between fiber tows, and the one‐dimensional Brinkman equation for flow in fiber tows. Three different textile fabrics are considered in the model: plain woven, 4‐harness, and bidirectional stitched fiberglass mats. The model incorporates the effect of porosity changes on permeability of fiber preforms under compression, which usually occurs in the molding process. To verify the validity of the model, the theoretical values are compared with a set of permeability measurements. Good agreement is found between the model prediction and the permeability measurements in the porosity ranges of ϕ ≤ 0.59 for plain woven fiber mats, ϕ ≤ 0.60 for 4‐harness fiber mats and ϕ ≤ 0.62 for bidirectional stitched fiber mats.     

Recycling of textile waste into green composites: Performance characterization

Recycling of any waste is as such a worldwide phenomenon. In this context application of textile waste for development of some value added product has been thought of in this work. Textile fabric waste is collected from various sources. These waste materials are garneted, so as to produce loose fibrous material. Subsequently this fibrous material was converted into nonwoven web and also twisted strand for manufacturing of 3D woven preforms to be used in composites. In case of nonwoven preforms, the webs are produced by combining polypropylene with cotton component with different proportions. Composites of various specifications are developed to examine their application in several end uses. These composite materials are characterized for their mechanical and thermal behavior in order to find out the response against tensile loading, impact force and thermal loading. The effects of moisture absorption on mechanical properties of these composites are investigated. As the percentage of PP fibres is increased in the web, mechanical performance of the composite material is improved in general. The exposure of composite material to high humidity condition has not shown any significant change in their mechanical behavior. 3D woven fabric reinforced composite produced by using garneted fibre yarn and virgin cotton OE yarn didn't exhibit any significant difference in the mechanical and thermal behavior of composite. The results confirmed that textile waste material can be safely used as reinforcing structure in composite manufacturing. POLYM. COMPOS., 35:1960–1967, 2014. © 2014 Society of Plastics Engineers     

Comparison of mechanical and ballistic performance of composite laminates produced from single‐layer and double‐layer interlocked woven structures

Textile structures have become quite popular as reinforcement materials in composite laminates due to their high impact‐damage tolerance and energy absorption ability. The impact performance of textile composites is not only affected by the type of fiber/matrix but also by the fabric structure used as reinforcement. The aim of this study was to compare the mechanical and ballistic performance of composite laminates reinforced with single‐layer and double‐layer interlocked woven fabrics. Kevlar^®−29 multifilament yarn was used for preparation of all the fabric structures and epoxy resin was used as the matrix system. The composites were produced using a hand lay‐up method, followed by compression molding. The mechanical and ballistic performance of composites reinforced with single‐layer and double‐layer interlocked woven fabrics was investigated in this study. The energy absorption and mechanical failure behavior of composites during the impact event were found to be strongly affected by the weave design of the reinforcement. The composites reinforced with double‐layer interlocked woven fabrics were found to perform better than those comprising single‐layer fabrics in terms of impact energy absorption and mechanical failure. POLYM. COMPOS., 35:1583–1591, 2014. © 2013 Society of Plastics Engineers     

Comprehensive performance characterization of conductive fabric made of reduced graphene oxide (rGO)

In this study, the production and comprehensive characterization of graphene based electrically conductive textile products, which will allow lower processing costs, such as, low temperature and short process times, and known textile production processes without losing their flexibility, lightness, permeability, and washability characteristics of textile products. Reduced graphene oxide (rGO) was applied with a single step process by impregnation to woven fabrics and various properties of fabrics related to performance and comfort were analyzed besides electrical conductivity. The results obtained in the study have shown that it is possible to produce flexible and soft conductive textiles with low resistance values below 100 kΩ, resistant to mechanical deformations, such as, bending, rubbing, and stretching (cyclic test). In addition, the findings indicated that the fabrics applied rGO with the one-step production process will provide significant advantages to the electronic textile market in terms of wearability, cost-effectiveness, and applicable processes.