织物-树脂复合材料层压板的准静态侵彻机理

本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。     

国外复合材料用高级增强纤维的发展现状

本文综述了国外碳纤维、陶瓷、聚芳酰胺、超高分子量聚乙烯、液晶聚合物纤维的发展现状,包括它们的生产能力、消费情况、性能特点,主要生产国和生产公司、产品牌号以及应用领域等,并指出了其生产进展和发展动向。     

Time-Temperature Superposition to Determine the Stress-Rupture of Aramid Fibres

Conventional creep testing takes a long time to obtain stress-rupture data for aramid fibres at the low stress levels likely to be used in practical applications. However, the rate of creep of aramid can be accelerated by a thermally activated process to obtain the failure of fibres within a few hours. It is possible to obtain creep curves at different temperature levels which can be shifted along the time axis to generate a single curve know as a master curve, from which stress-rupture data can be obtained. This technique is known as the time-temperature superposition principle and will be applied to Kevlar 49 yarns. Important questions relating to the techniques needed to obtain smooth master curves will be discussed, as will the validity the resulting curves and the corresponding stress-rupture lifetime.     

Vibrations of an aramid anchor cable subjected to turbulent wind

The vibration response of an initially pre-stressed anchor cable made of parallel-lay aramid fibres excited by a measured and artificially simulated spatial turbulent wind field is presented in the paper. Results of the analyses of in situ measured wind records are described. For selected data set statistical characteristics and power spectral density functions of the measured wind velocity components are calculated. The wind stochastic velocity fluctuation is modelled as a one-variate bi-dimensional random field. Cross-power spectral density functions, at different point locations are introduced. The combination of the weighted amplitude wave superposition method (WAWS) with the Shinozuka–Deodatis method is used for the analyzed problem. A time-dependent behaviour of the synthetic cable is investigated which is subjected to turbulent wind with large expected oscillations that arise as a result of slackening due to the relaxation effects. A nonlinear transient dynamic analysis is used in conjunction with the finite element method to determine the dynamic response of the cable subjected to turbulent wind at its initially prestressed state and in the selected times after the relaxation effect. The constitutive equation of the relaxation of the aramid cable follows an experimentally obtained law of the logarithmic type. To monitor the dependences of the individual quantities of cable vibration in the phase space, attractors and Poincaré maps are created by sampling the cable’s displacement and velocity at periods of relevant frequencies. Interesting findings based on the response of the cable with rheological properties to turbulent wind are presented.     

塑化拉伸对芳纶Ⅲ结构性能的影响

芳纶Ⅲ主要采用湿法纺丝,在纺丝成形过程中须经过凝固浴,常采用一凝和二凝凝固成形,其中二凝塑化拉伸比对芳纶Ⅲ的结构及性能有显著影响。对二凝拉伸比进行了系列试验,通过X射线衍射、声速取向度、干纱及浸胶丝力学性能对比分析了凝固浴拉伸对芳纶Ⅲ结构与性能的影响。     

Research Advancement in High-Performance Polyamides and Polyamide Blends Loaded with Layered Silicate

Polyamide comprises one of the major classes of polymers. Layered silicates (nanofiller) may enhance properties of polyamide-based hybrids even at very low content. Aliphatic polyamides (nylons) have often been chosen for commercial applications because of excellent physical and chemical properties. Aromatic polyamides (aramids) and aliphatic-aromatic polyamides have been predominantly useful as high-performance materials due to stiffness, low density, and low cost. Recently polyamide blends have become an important route to high-performance materials. Binary blends of polyamide/polypropylene, polyamide/polystyrene, polyamide/polymethyl methacrylate, polyamide/polyurethane, and others have been reported for nanocomposite formation with organoclay. However, ternary blend nanocomposite with nanoclays (PA6/mSEBS, PA6/EPDM-g-MA/H-HDPE) is rarely explored.     

芳纶Ⅲ在复合材料领域应用的优势探讨

芳纶Ⅲ属于对位杂环芳纶,因其独特的分子结构和工艺技术而具有低密度、超高强度、超高模量、耐高温、抗冲击性好、耐磨性好、透波性好等优良性能,是综合性能最好的有机纤维之一。芳纶Ⅲ及其复合材料在飞机部件(螺旋桨、轮胎、机身、主翼、尾翼等部位)、星载/机载/舰载雷达罩、卫星部件、防弹材料(高级防弹衣、防弹头盔、防弹护甲)、兵器、特种绳索等领域有着广泛的应用。     

2D Ti3C2Tx MXene/aramid nanofibers composite films prepared via a simple filtration method with excellent mechanical and electromagnetic interference shielding properties

Electromagnetic shielding (EMI) materials are becoming more and more important because of the increasingly serious radiation pollution. The preparation of high mechanical strength, ultrathin, lightweight, flexible materials with excellent EMI shielding performance have so far been elusive. Here, we try to prepare an ultrathin, lightweight and flexible film with excellent EMI shielding performance using one-dimensional aramid nanofibers (ANFs) and two-dimensional few-layered Ti₃C₂T_x through a simple filtration method. The ultimate tensile strength and strain of the film are up to 116.71 MPa and 2.64%. The EMI shielding effectiveness and the specific EMI shielding efficiency are 34.71 dB and 21971.37 dB cm² g⁻¹, which will be no recession after 1000 times bending. Our results show that a practical EMI shielding material with excellent performances has been successfully prepared, which will be widely applied in wearable electronics, robot joints, and precision instrument protection and so on.     

The Influence of Temperature on the Tensile Properties and Residual Strain Following Stress-relaxation Processes of Armos and Terlon Aramid Yarns

Abstract

Aromatic polyamide fibres occupy a unique position among synthetic fibres due to their superior mechanical and thermal properties. Armos and Terlon are of particular interest as initial raw material for the production of high-strength, high-modulus and heat-resistant aramid fibres and yarns. This study investigates the influence of temperature on the strength and deformation properties of these yarns. It is found that the characteristics of tensile stress– strain properties and the accumulation of residual deformation are temperature dependent, especially in the case of Armos. The mechanical properties are strongly influenced by the level of moisture which is associated with intermolecular interaction such as hydrogen bonds and Van der Waals forces.     

The Friction and Wear of Aramid Fiber-Reinforced Polyamide 6 Composites Filled with Nano-MoS2

The friction and wear behaviors of aramid-filled PA 6 composites filled with and without nano-MoS₂ were investigated on an end-face tribometer through rubbing against ASTM 1045 steel under dry friction. The experimental results indicated that the wear rate and the friction coefficient of PA 6 decreased with the addition of nano-MoS₂. The friction coefficients of PA 6 composites filled with aramid fiber are lower than those without nano-MoS₂. The main wear mechanisms under dry sliding condition are the plastic deformation and mechanical microploughing. For best combination of friction coefficient and wear rate, the optimal volume content of MoS₂ in the composites appears to be 10 vol %.