提高芳纶无纬布产品质量的措施

本文介绍了芳纶无纬布在制备过程中影响其质量的主要因素,如纤维所受张力大小、树脂含量、制备过程中的温、湿度等环境条件控制等。在实际摸索过程中总结出影响无纬布质量的这些因素,可以有效指导在日常生产过程中出现的产品质量问题,也能通过合理有效地控制影响产品质量的因素,制备出性能稳定、质量符合要求的无纬布产品。在实践中摸索出的一系列工艺技术参数,可以直接指导车间工人根据这些参数指标来指导生产,从而保证产品的高品质。     

芳纶纸蜂窝及其夹层结构的研究进展

本文综述了目前芳纶纸蜂窝及其夹层结构在制备、性能以及应用方面的研究成果及进展,指出芳纶纸蜂窝以其各项优异的性能广泛的应用于各行业中,并且逐步成为不可或缺的材料之一.芳纶纸是制备蜂窝材料及其夹层结构的最根本原材料,其国产化迫切需要进行.     

集成竹拉伸蠕变性能加速试验

通过短期(500 h)拉伸蠕变试验,研究了不同应力水平下集成竹顺纹拉伸蠕变行为及变化规律,采用了Findley蠕变模型对蠕变曲线进行模拟;通过阶梯等温法加速蠕变试验,对集成竹顺纹拉伸长期蠕变行为进行了加速表征,构建了跨度50年的蠕变主曲线。结果表明：不同应力水平下,集成竹拉伸蠕变曲线具有初始蠕变和稳态蠕变两个阶段;集成竹拉伸蠕变行为符合线性黏弹性,在任意时刻,其蠕变变形基本与应力水平成正比;根据蠕变主曲线,在60%极限荷载下,集成竹约在104天发生蠕变断裂,呈现脆性破坏形态;Findley蠕变模型不仅能较好地模拟集成竹短期拉伸蠕变行为,其外推结果与加速蠕变试验所得主曲线吻合良好。基于上述试验结果与分析,建立了考虑材料蠕变效应的等时应力-应变曲线,进一步讨论了针对不同设计使用年限的集成竹弹性模量调整系数,并与GB/T 50005—2017《木结构设计标准》建议值进行了对比。     

竹集成材钉节点抗剪性能试验研究

通过短期(500 h)拉伸蠕变试验,研究了不同应力水平下集成竹顺纹拉伸蠕变行为及变化规律,采用了Findley蠕变模型对蠕变曲线进行模拟;通过阶梯等温法加速蠕变试验,对集成竹顺纹拉伸长期蠕变行为进行了加速表征,构建了跨度50年的蠕变主曲线。结果表明：不同应力水平下,集成竹拉伸蠕变曲线具有初始蠕变和稳态蠕变两个阶段;集成竹拉伸蠕变行为符合线性黏弹性,在任意时刻,其蠕变变形基本与应力水平成正比;根据蠕变主曲线,在60%极限荷载下,集成竹约在104天发生蠕变断裂,呈现脆性破坏形态;Findley蠕变模型不仅能较好地模拟集成竹短期拉伸蠕变行为,其外推结果与加速蠕变试验所得主曲线吻合良好。基于上述试验结果与分析,建立了考虑材料蠕变效应的等时应力-应变曲线,进一步讨论了针对不同设计使用年限的集成竹弹性模量调整系数,并与GB/T 50005—2017《木结构设计标准》建议值进行了对比。     

The Transfer of Fibres in the Carding Machine

The problem of understanding the transfer of fibres between carding-machine surfaces is addressed by considering the movement of a single fibre in an airflow. The structure of the aerodynamic flow field predicts how and when fibres migrate between the different process surfaces. In the case of a revolving-flats carding machine the theory predicts a “strong” aerodynamic mechanism between taker-in and cylinder and a “weak” mechanism between cylinder and removal cylinder resulting in effective transfer in the first case and a more limited transfer in the second.     

植物纤维泡沫包装材料的研究

研究了利用天然植物纤维材料,经发泡制成降解型泡沫包装材料的工艺技术,对产品抗震缓冲性能作了初步测试分析,提出了一种开发新型内包装材料的方法。     

超临界二氧化碳协助改性芳纶纤维的表面性能

本文用超临界二氧化碳流体做反应介质,利用其超强的扩散性及溶解渗透性,将甲苯-2,4-二异氰酸酯(TDI)带到芳纶纤维表面进行渗透并发生接枝、扩链反应,通过红外光谱、扫描电镜、x-射线光电子能谱方法、AFM等测试了纤维的表面形貌变化及元素、基团变化,并用VARI成型技术制成复合材料,测试了改性芳纶布与环氧基体的力学性能和界面性能。结果表明:经改性的纤维表面变得粗糙,极性基团增加,复合材料界面剪切强力明显增加,改性复合材料力学性能及界面得到改善,纤维更适合用作复合增强材料。     

国产粘胶基碳纤维强度的两种统计分布

测定了粗细不同的两种粘胶原丝及其碳纤维的单丝强度,并用Ｇａｕｓｓ和Ｗｅｉｂｕｌｌ两种方法对比其分布进行了对比分析研究。     

由醋酸锆前驱体制备ZrO_2连续纤维的过程及研究

为了制得耐高温、高强度的氧化锆连续纤维,利用新制醋酸锆作为前驱体,通过溶胶－凝胶法合成含有Ｚｒ－Ｏ长链的溶胶,干法纺丝,制备ＺｒＯ２连续纤维．研究了醋酸锆的光谱和热学性质,并对烧结后的纤维做扫描电镜观察、ＸＲＤ分析和纤维抗拉强度的测试．测试结果表明醋酸锆前驱体溶胶中含有以Ｚｒ－Ｏ为骨架的长链,具有良好的可纺性和稳定性．直径在十几个微米以下的连续纤维具有一定的强度和韧性,添加 ５ｍｏｌ％的 Ｙ２Ｏ３可将 ＺｒＯ２的晶相稳定在四方相．     

Environmental Durability of Flax Fibres and their Composites based on Polypropylene Matrix

The environmental degradation behaviour of flax fibres and their polymer composites are explored. New upgraded Duralin flax fibres, which have been treated by a novel treatment process for improved moisture and rot sensitivity were studied. Environmental studies showed that these upgraded Duralin flax fibres absorb less moisture than untreated Green flax fibres, whereas the mechanical properties of the treated fibres were retained, if not improved. The effect of this novel flax fibre treatment on the environmental behaviour of natural-fibre-mat-reinforced thermoplastics (NMTs) is investigated by monitoring the moisture absorption and swelling, and measuring the residual mechanical properties of the flax/polypropylene composites at different moisture levels. The moisture absorption and swelling of the upgraded flax fibre composites is approximately 30% lower than that of composites based on Green flax fibres.     

The Non-Linear Viscoelastic Response of Polycarbonate in Torsion: An Investigation of Time-Temperature and Time-Strain Superposition

Data are presented from torsional stress relaxationexperiments on a commercial polycarbonate. Tests were performedon samples over a range of torsional strains from 0.0025 to 0.08and at temperatures from 30 to 110°C at a fixed aging time of64,800 s (18 h). Following the scaling approach of Penn andKearsley [Trans. Soc. Rheol. 20 (1976)] we were able todetermine the stress relaxation response at shear strains to0.07. Then the individual data sets at each strain andtemperature could be described using a stretched exponential formrelaxation function. Over the range of temperatures studied thedata at each strain were superimposed using conventional time-temperature superposition. For strains up to the yield strainthe data at each temperature could also be superimposed to form amaster curve following the principle of time-strainsuperposition. Interestingly, the master curves found from time-strain superposition at each temperature did not have the sameform. Similarly, the master curves found from time-temperaturesuperposition at each strain did not have the same form.     

预分散芳纶短纤维莱茵能AFP-40／EPDM和莱茵能P91—40／EPDM的应用研究

研究了预分散芳纶短纤维莱茵能AFP-40／EPDM和莱茵能P91—40／EPDM在EPDM胶料中的性能。结果表明,在动静态负载下,芳纶短纤维能提供很高的强度,尤其在纤维的取向方向,即使很小的应变,也会产生很高的定伸应力;芳纶短纤维具有优异的耐高温应力和耐化学介质腐蚀性能;莱茵能AFP-40／EPDM和莱茵能P91-40／EPDM预分散芳纶纤维会在胶料中得到较为理想的分散性,通过强度,动态阻力和纤维形态的分布方面测试对比,莱茵能AFP-40／EPDM在胶料中能提供最好的分散性,莱茵能AFP和莱茵能P91系列的产品可用于高性能材料制品。     

Application of Stereovision to the Mechanical Characterisation of Ceramic Refractories Reinforced with Metallic Fibres

Abstract:  Optical methods that yield displacement or strain fields are now emerging significantly in the mechanical sciences. At the Research Center on Tools, Materials and Forming Processes (CROMeP) at École des Mines d'Albi, a binocular stereovision system has been developed that can be used to measure: (a) the three-dimensional (3D) shape of a static object, or (b) the surface strains of an object undergoing some 3D mechanical or thermal stress. In this paper, the application of the stereovision technique to investigate the behaviour of ceramic refractories reinforced with metallic fibres is presented: (i) after the rupture of the sample for assessing the 3D orientation of the fibres in order to correlate a micro-mechanical model of fibre pullout with the macro-mechanical results of tensile tests, and (ii) during a tensile test for measuring the 3D displacement/strain field around a notch.     

Application of Nonlinear Superposition to Creep and Relaxation of Commercial Die-Casting Aluminum Alloys

Die-cast aluminum alloys are heavily used in small engines, where they are subjected to long-term stresses at elevated temperatures. The resulting time-dependent material responses can result in inefficient engine operation and failure. A method to analytically determine the stress relaxation response directly from creep tests and to accurately interpolate between experimental time-history curves would be of great value. Constant strain, stress relaxation tests and constant load, creep tests were conducted on aluminum die-casting alloys: B-390, eutectic Al–Si and a 17% Si–Al alloy. A nonlinear superposition integral was used to (i) interpolate between empirical primary inelastic creep-strain and stress-relaxation time histories and (ii) to determine the stress relaxation response from corresponding creep data. Using isochronal stress-strain curves, prediction of the creep response at an intermediate stress level from empirical creep curves at higher and lower stresses resulted in a correlation (R) of 0.98. Similarly for relaxation, correlations of 0.98 were obtained for the prediction of an intermediate strain level curve from higher and lower empirical relaxation curves. The theoretical prediction of stress relaxation from empirical creep curves fell within 10% of experimental data.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Mechanics of Time-Dependent Materials     

丝素蛋白/乙二醇二缩水甘油醚对老化丝纤维的加固

在制备人工老化样的基础上,利用丝素蛋白/乙二醇二缩水甘油醚对老化丝纤维进行加固,并对加固前后的丝纤维进行了性能和结构表征。研究结果表明,丝素蛋白与乙二醇二缩水甘油醚发生了化学反应;反应位点为Tyr羟苯基上的羟基、Lys上的氨基、His咪唑基上的亚氨基等;加固样的断裂强力从1.54 N提高到15.8 N,伸长率从2%提高...     

Preparation and characterization of aluminium alloy sheet Aramid fibre-laminated composites

Laminated composites consisting of alternate layers of aluminium alloy sheets and unidirectional Kevlar-49 fibre epoxy composites were prepared using two different aluminium alloys DTD 687 and aluminium-lithium alloy. Tensile, compressive and interlaminar shear strengths of the laminates were measured. The residual stresses in the aluminium alloy sheets arising out of thermal mismatch between aluminium alloys and aramid fibres were also measured. It is found that the laminates have lower density, higher tensile strength and marginally lower Young’s modulus as compared with monolithic alloy sheets.     

Terahertz spectroscopy to study the orientation of glass fibres in reinforced plastics

We employ terahertz time-domain spectroscopy (THz TDS), a novel, non-destructive testing method, to study the fibre orientation and fibre content in reinforced plastics. The birefringent properties of plastics filled with differing amounts of short glass fibres are measured at frequencies from 100 GHz up to 1 THz. To predict the permittivity of the experimentally examined composite materials, we use an effective medium theory first introduced by Polder and van Santen. On the basis of the measured data and this model, we deduce the additive content ξ, the preferential orientation of the fibres φ and the fraction of orientated fibres a. Our findings agree well with corresponding mold flow simulations performed with commercially available software.     

Artificial Neural Network for Creep Behaviour Predictions of a Parallel‐lay Aramid Rope Under Varying Stresses

Abstract: An improvement of the creep behaviour prediction of parallel‐lay aramid ropes under varying stresses is the scope of the following study in which application of artificial neural networks (ANNs) for the prediction of creep under varying stresses is presented. This qualitatively different approach assumes that the ANN can be trained to simulate time‐dependent response of the rope in the given load (stress) programme and time interval. The classic rheological constitutive equations are not needed in this case, because ANN acts as a constitutive operator trained by stresses and the corresponding creep strains from experimental data. Carried numerical experiments were divided into the following three parts: (i) searching the best ANN for a creep behaviour approximation under varying stresses, (ii) investigating the best topology of the selected neural network and (iii) investigating the best results for the creep function identification. Comparison between the experimentally observed creep strains of the parallel‐lay aramid rope under varying stresses, predicted creep strains when the linear creep constitutive equation is applied and predicted creep strains when the obtained Jordan neural network with the 3‐10‐1 topology is used confirmed that the Jordan neural network developed achieved less than half mean square error beside the existing creep constitutive analytical approach.