Electrical Properties of Polyethylene Composites with Low Content of Neodymium

The effects of Neodymium (Nd) on the electrical properties of low density polyethylene in relation with morphological aspects are reported in this article. Scanning electron microscopy and optical microscopy revealed a quasi-uniform dispersion of Nd particles in polyethylene, both individual particles and clusters being observed. Contact angle measurements showed a decrease of contact angle values and, thus, of surface hydrophobicity, with the increase of Nd content. The addition of Nd in polyethylene determined the increase of electric permittivity and conductivity. The variation of permittivity was explained considering the influence of polar species (additives, oxidation products, neodymium oxide), highlighted by Fourier transform infrared analysis.     

Pilot plant studies on the removal of trihalomethanes by composite reverse osmosis membranes

The effect of single trihalomethane (THM) (CHCl₃) content in various types of water on the performance of two types of reverse osmosis composite membranes (the AFC99 membrane in tubular module B1, PCI, and the FT30 membrane in a spiral-wound element BW3040, FilmTec) have been investigated. The performance of these membranes in RO tests carried out using distilled water, tap water and brackish water (1000–5000 ppm NaCl) with the addition of THM have been evaluated in terms of permeate flux and the rejection of dissolved solids and THM. The FT30 membrane provided THM rejection better than 99.5% during the reverse osmosis treatment of tap water and brackish water. The AFC99 membrane exhibited only 80% retention of THM, obtained for the transmembrane pressures in the range of 10 to 30 bars. It was found that the presence of CHCl₃ slightly affects the transport and separation properties of the composite membranes used.     

Desirability based multiobjective optimisation of abrasive wear and frictional behaviour of aluminium (Al/3.25Cu/8.5Si)/fly ash composites

Aluminium alloy (Al/3.25Cu/8.5Si) composites reinforced with fly ash particles of three different size ranges (53–75?μm, 75–103?μm and 103–125?μm) in 3, 6 and 9 wt-% were fabricated using liquid metallurgy technique. Pin on disc abrasive wear tests were carried against the disc surface fixed with SiC emery paper (120 grades). A mathematical model was developed to predict the abrasive wear and coefficient of friction of the composites. Analysis of variance technique was used to check the validity of the developed model. Composites reinforced with coarse fly ash particles exhibited better abrasive wear resistance than those reinforced with fine fly ash particles. Abrasive wear in composites with fine fly ash particles is a combination of adhesive wear and abrasive wear. Larger fly ash particles present in composites gets fractured into fine particles and entrapped between the composite pin and the disc, thereby decreasing the wear rate. Worn surfaces of the pins were then analysed using scanning electron microscopy to study the wear mechanisms of the composites. The abrasive wear was optimised using desirability based multiobjective optimisation technique.     

Corrugated laminate homogenization model

This work addresses the problem of finding a substitute material model for describing the load response of globally flat corrugated sheets made from multidirectional laminates. Exact solutions of the equations governing thin singly curved shells give the displacements, strains and stresses within a unit cell extending over one period of the corrugation pattern. The forces reacting to enforced unit deformations determine the constitutive law of the substitute material model. The analytical results are compared with those of finite-element models.     

Buckling analysis for delaminated composites using plate bending elements based on higher‐order zig‐zag theory

A finite element based on the efficient higher‐order zig‐zag theory with multiple delaminations is developed. The bending part of the formulation is constructed from the concept of DKQ element. Unlike conventional elements, a developed element has its reference in the bottom surface which simplifies zig‐zag terms on formulation. Exact patch solutions are developed on elements which have the bottom reference system. The present element passes proper bending patch tests in the arbitrary mesh configurations in isotropic materials. Zig‐zag formulation is adopted to model laminated plates with multiple delaminations. To assess the accuracy and efficiency of the present element based on higher‐order zig‐zag theory with multiple delaminations, the linear buckling problem of laminated plates with multiple delaminations has been analysed. The results have been compared with three‐dimensional elasticity solutions. The present element works as an efficient tool for analysing the behaviour of the laminated composites with multiple delaminations. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance of shear connection in composite beams with profiled steel sheeting

This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear finite element model was developed to study the behaviour of headed stud shear connectors welded through-deck. The profiled steel sheeting had transverse ribs perpendicular to the steel beam. The material nonlinearities of concrete, headed stud, profiled steel sheeting, reinforcement and steel beam were included in the finite element model. The capacity of shear connection, load-slip behaviour of the headed stud, and failure modes were predicted. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to study the effects on the capacity and behaviour of shear connection by changing the profiled steel sheeting geometries, the diameter and height of the headed stud, as well as the strength of concrete. The capacities of shear connection obtained from the finite element analysis were compared with the design strengths calculated using the American Specification, British Standard and European Code for headed stud shear connectors in composite slabs with profiled steel sheeting perpendicular to the steel beam. It is found that the design rules specified in the American and British specifications overestimated the capacity of shear connection, but the design rules specified in the European Code were generally conservative.     

受负弯矩和压缩作用的组合梁的性能和设计

调查了受负弯矩和轴向压缩共同作用下钢-混凝土组合梁结构的性能。在这项研究中,对6个承受负弯矩作用的足尺寸的组合梁同时进行压缩。轴向压缩的等级由低到高变化。根据试验,构建并标定一个非线性有限元模型来对试验结果进行验证。该模型能够对试验所用梁的非线性响应和最终破坏模式做出预测。所构建的有限元模型对一些常在实际中使用的组合梁可进行一系列参数分析。分析发现,当压缩荷载作用于组合截面时,组合梁的负弯矩承载能力明显降低,钢梁的局部屈曲更显著,影响了截面的延展性。基于截面平衡的刚塑性分析可以合理地预测组合截面的复合强度,因此可适当地使用于设计原理中。在负弯矩区钢梁腹板处使用纵向加劲肋可消除腹板屈曲,并增加组合截面的转动能力。根据试验结果和有限元分析提出一个可应用于工程实践中的简化设计模型。     

组合剪力墙的滞回性能评价

组合型钢剪力墙刚度大、延性好,在土木工程中应用广泛。组合型钢剪力墙一般通过铺设与钢板连接的混凝土层或纤维增强复合板形成。本试验和数值研究主要分析剪力钉间距、中梁刚度、梁柱连接方法对组合型钢剪力墙性能的影响。结果表明:增大剪力钉间距可减小荷载-位移曲线的斜率,并提高结构韧性。中梁刚度和梁柱连接对组合型钢剪力墙性能的影响是非常微小的,可以忽略。     

组合剪力墙的滞回性能研究

组合型钢剪力墙刚度大、延性好,在土木工程中应用广泛。组合型钢剪力墙一般通过铺设与钢板连接的混凝土层或纤维增强复合板形成。本试验和数值研究主要分析剪力钉间距、中间梁刚度、梁柱连接方法对组合型钢剪力墙性能的影响。结果表明:增大剪力钉间距可减小荷载-位移曲线的斜率,并提高结构韧性。中间梁刚度和梁柱连接对组合型钢剪力墙性能的影响是非常微小的,可以忽略。     

The influence of profiled sheeting thickness and shear connector’s position on strength and ductility of headed shear connector

A three-dimensional finite element model is developed, validated and used in the parametric study to investigate the influence of shear stud’s position and profiled sheeting thickness on the strength, ductility and failure modes of the headed shear stud welded to the modern profiled sheeting. A total of 240 push tests were analysed with different sheeting thicknesses, positions of the shear stud in the trough, concrete strengths and transverse spacings. The results showed that the sheeting thickness influenced the shear connector resistance of studs placed in the unfavourable position more than studs placed in favourable and central positions. The strength of the shear connector placed in the unfavourable position increased by as much as 30% when the sheeting thickness was increased. The shear connector resistance of the unfavourable stud was found to be primarily a function of the strength and the thickness of the profiled sheeting rather than the concrete strength. The strength prediction equations for unfavourable and central studs were also proposed. The results suggested that the strength of the shear connector increased as the distance of the shear stud increased from the mid-height of the deck rib in the load bearing direction of the stud. The load-slip behaviour of the studs in the unfavourable position was more ductile than the studs in the favourable position, with slip of 2-4 times higher. It was found that the increase in sheeting thickness and transverse spacing improved the ductility of the stud in unfavourable position, but had no effect on the stud in the favourable position. The failure modes suggested that the favourable and central studs failed by concrete cone failure and unfavourable studs failed by rib punching together with crushing of the narrow strip of the concrete in front of the stud.