复合材料预制件－三维正交互锁机织物的试验研究

本文分析了用于复合材料预制件的三维机织物的结构与成形类别,通过样品试制,阐述了利用普通织机制织三维正交互锁机织物的结构特征、织造原理与方法。     

弧焊机器人摆动跟踪时摆幅与频率的模糊模式识别

针对10 mm厚钢板V形坡口接头的弧焊机器人摆动跟踪焊接,实时测量电弧电压和焊接电流的瞬时值,对其进行两次统计处理,构建不同摆幅和摆动频率时的焊接电参数特征矢量,采用模糊模式识别技术,建立了焊接电参数特征矢量与摆动焊接摆幅和频率的内在联系,为定量研究摆幅和频率对V形坡口焊缝成形的影响提供依据。     

Characterisation of polylactic acid biocomposites made from prepregs composed of woven polylactic acid/hemp–Lyocell hybrid yarn fabrics

This paper describes the mechanical properties and water absorption characteristics for biocomposites made from woven PLA/hemp/Lyocell prepregs. The aim was to improve the properties with the addition of Lyocell fibre into a hybrid yarn. Well-aligned hybrid yarns composed of hemp/PLA, hemp–Lyocell/PLA, respective, Lyocell/PLA were made by wrap spinning. Unidirectional satin fabrics were made by weaving with PLA (warp) and the hybrid yarns (weft). Uniaxial composites were fabricated with 30 fibre mass% using compression moulding. The composites were investigated for tensile, flexural and impact properties. Combining hemp with Lyocell in a PLA matrix improves the mechanical properties, compared to hemp/PLA composites. The composite made from the satin Lyocell/PLA fabric gave the best mechanical properties. The type of fibre reinforcement compositions did not significantly affect the water absorption of the biocomposites. Scanning electron microscopy showed that fibre pull-outs appear more often in hemp/PLA composites than in composites also including Lyocell fibre.     

Construction of unpaved rural road using jute–synthetic blended woven geotextile – A case study

Jute–high density polyethylene (HDPE) blended geotextile samples produced using HDPE slit-film in the machine direction and jute yarn in the cross direction for use in the construction of unpaved rural roads. Use of HDPE slit-film resulted in high productivity of jute-based geotextiles in modern high-speed machines, while jute (≈85%) in cross direction resulted in notable increase in modulus, breaking strength, CBR puncture resistance of the blended geotextile as compared to 100% HDPE geotextile. The optimized geotextile (plain-weave fabric with 111 tex HDPE in machine direction, 2 × 360 tex jute yarn in cross direction having area density, 316 g/m²) was used in a field trial. During road construction, the geotextile was covered with a layer of 10 cm thick laterite gravels as the sub-grade, compacted by rolling, and then finally covered with 10 cm small granular lateritic stones, and rolled again. The field trial showed that the monitored section where geotextile was used showed an even surface without any notable subsidence or rutting after 18 months. However in sections of the road constructed without the geotextile, 5–35 mm deep ruts were observed. CBR tests (carried out 11 months and 18 months after construction) showed a 67–73% improvement in the road due to the use of jute–HDPE blended geotextile than that obtained for the part of the road where geotextiles were not used.     

无PVA上浆的现状与展望(下)

探讨应用高性能变性淀粉取代PVA上浆的配方、工艺及上浆效果.对二十家纺织企业生产的纯棉品种及涤棉混纺品种应用高性能变性淀粉取代PVA上浆的配方、浆纱工艺、织造效果进行了汇总,并与用PVA上浆的配方进行了时比.指出:应用高性能变性淀粉取代PVA上浆,有利于提高浆纱好轴率、提高下机一等品率、降低用浆成本、提高印染质量.     

Characterization of thermoplastic natural fibre composites made from woven hybrid yarn prepregs with different weave pattern

This paper focuses on the effect of weave structure on mechanical behaviour and moisture absorption of the PLA/hemp woven fabric composites made by compression moulding. The unidirectional woven fabric prepregs were made from PLA (warp) and PLA/hemp wrapped-spun hybrid yarn (weft) with two different weave patterns; 8-harness satin and basket. Unidirectional composites with 30 mass% hemp content were fabricated from these prepregs, and compared to winded PLA/hemp hybrid yarn laminates with same composition. The composite from the satin fabric had significantly lowest porosities and best mechanical properties compared to the composite made from the winded hybrid yarn and basket fabric. The tensile, flexural, and impact strength were 88 MPa, 113.64 MPa, and 24.24 kJ/m², respectively. The effect of weave pattern on water absorption is significant. Although the composite from hybrid yarn laminate has larger water absorption than that of the pure PLA, it exhibits lower moisture absorption than both weaves.     

Using the expert system to analyze loom performance

In this paper, the development of a warp tension simulation is presented. A system analysis of modern weaving machines led to a suitable simulation model to calculate the warp tension. The validation of the simulation demonstrates that the results correspond well with reality. In a second step, an improved model of this simulation was used in combination with a genetic algorithm and a gradient-based method to calculate optimized setting parameters for the weaving process. In order to do so, a cost function was defined taking into account a desired course of the warp tension. Actually, it is known, that a low and constant warp tension course is suitable for weaving. Using the genetic algorithm or the gradient-based method leads to optimized weaving machine parameters. Both algorithms do get nearly the same results for the optimized weaving machine setting. Applying the optimized setting parameters on a loom did not demonstrate that the productivity of a weaving machine can be raised. Analysis of the produced fabrics did not show an influence of optimization on the fabric quality. The reduction of warp tension was not sufficient in order to have an impact on the mechanical properties of the fabric. Thus, fabric defects could be eliminated using the optimized weaving machine settings.     

原液染色涤纶帐篷布的生产要点

探讨原液染色涤纶帐篷布的生产要点。针对帐篷布的使用环境,介绍了选用的米黄色、翠绿色染色涤纶的性能要求;生产中,针对染色涤纶纤维的特点,采取了一系列技术措施,如适当提高清棉各打手速度、增加锡林与盖板间隔距、并条选用硬度稍大的胶辊、选用稍小的粗纱捻系数、逐锭校正摇架压力、降低络筒速度、合理配置整经张力等,最终纺制的两种纱成纱质量和帐篷布质量指标均达到了设计要求。认为:认真落实各工序的关键技术措施是保证原液染色涤纶帐篷布质量的关键。     

Properties of yarn pull-out in para-aramid fabric structure and analysis by statistical model

The aim of this study is to analyze and determine the pull-out properties of para-aramid woven fabrics. Para-aramid Kevlar29® and Kevlar129® woven fabrics were used to conduct the pull-out tests. They have high and low fabric densities. A yarn pull-out fixture was developed to test various fabric sample dimensions. Data generated from single and multiple yarn pull-out tests in various dimensions of Kevlar29® and Kevlar129® woven fabrics included fabric pull-out forces, yarn crimp extensions in the fabrics and fabric displacements. The regression model showed that yarn pull-out forces depend on fabric density, fabric sample dimensions and the number of pulled ends in the fabric. Yarn crimp extensions depend on the crimp ratios of the fabric and fabric density. Fabric displacements depend on fabric sample dimensions and the number of pulled yarns.     

Naturalistic conversation improves daytime motorway driving performance under a benzodiazepine: A randomised,crossover, double-blind,placebo-controlled study

The adverse effects of benzodiazepines on driving are widely recognised. The aims of this study were both to determine the impact of naturalistic conversation on the driving ability of drivers under a benzodiazepine, and to measure the accuracy of drivers’ assessments of the joint effects of the benzodiazepine and conversation. Sixteen healthy male participants (29.69 ± 3.30 years) underwent a randomised, crossover, double-blind, placebo-controlled study with the benzodiazepine lorazepam (2 mg). They drove 200 km (125 miles) on a motorway in the morning. We measured two driving ability-related variables (i.e., lane-keeping performance), and collected a set of self-assessed variables (i.e., self-assessment of driving performance) during two 10-min sequences of interest (no conversation vs. conversation). An analysis of variance revealed an interaction whereby lane-keeping performance under lorazepam was worse in the no-conversation condition than in the conversation condition. No such difference was detected under placebo. Pearson's correlation coefficients revealed that self-assessments were (i) not at all predictive of lane-keeping when performed before the drive, but (ii) moderately predictive of lane-keeping performance when performed during or after the drive. We conclude that conversation with a passenger may contribute to safer lane-keeping when driving under a benzodiazepine. Moreover, a degree of awareness may be attained after some experience of driving under the influence of this type of medication.