Evaluation of fire testing procedures for combustible materials and building elements from the structural engineering viewpoint

The burning characteristics of building materials are discussed. For assessing the fire behaviour of structural materials the following properties are relevant: combustibility, flame spread, and heat contribution. These characteristics are determined in different laboratory tests. However, the fire performance of structural elements in situ is of much greater importance with regard to fire protection in structures, and the resistance to fire and fire propagation are the most important criteria. International unification is proposed in the testing of fire propagation.     

流变材料长期力学性能加速表征的若干进展

材料力学性能的时间相关特性对结构设计非常重要,尤其是长期力学性能的准确信息是结构强度和寿命分析的基础.结合近期研究进展,对影响高聚物时间相关力学性能和长期力学加速表征的主要因素进行了分析,对高聚物等流变材料长期力学性能的加速表征方法和技术以及涉及的基础问题进行了简要评述.     

Study of the influence of the structural grain size on the mechanical properties of technical materials

The mechanical properties of technical materials depend on their structure. They are influenced not only by their chemical composition, but particularly by the structural grain size. Significant changes in the mechanical behaviour of materials are related both to surface and volume properties, and not only in the field of mechanical parameters. A wide range of physical and chemical parameters changes as well. Nano‐materials are the materials, the structural grain size of which is in the dimensional area from 10^?9 to 10^?7 m. Nano‐particles and nanostructures are thus so small that their behaviour is affected by atomic forces, properties of chemical bonding, and quantum phenomena. The wave nature of the very small particles begins to manifest itself. The aim of the authors is to contribute by their paper to the solution of the problems in the field of material engineering. This means to investigate the specifics in the behaviour of technical materials depending on the change in the structural grain size towards the nano‐areas, as well as the design and use of new techniques of mathematical and physical modelling including the operative measurement method.     

Review of nanocarbon-engineered multifunctional cementitious composites

As structural materials, cementitious materials are quasi-brittle and susceptible to cracking, and have no functional properties. Nanotechnology is introduced into cementitious materials to address these issues. Nano materials, especially nano carbon materials (NCMs) were found to be able to improve/modify the mechanical property, durability and functional properties of cementitious materials due to their excellent intrinsic properties and composite effects. Here, this review focuses on the recent progress of fabrication, properties, and structural applications of high-performance and multifunctional cementitious composites with NCMs including carbon nanofibers, carbon nanotubes and nano graphite platelets. The improvement/modification mechanisms of these NCMs to composites are also discussed.     

Effect of low temperature on plastic deformation in structural materials in a complex state of stress

The results of experimental studies of elastoplastic deformation in structural materials of different grades in a complex state of stress at low temperatures are analyzed. It is shown that the degree of the effect of temperature and force conditions on the character of materials’ strain hardening at low temperature depends on their nature and structural state. The principal hypotheses and postulates that form the basis of the modern plasticity theories are examined for low temperatures. Two new models are introduced to describe the elastoplastic deformation of quasi-brittle and metastable materials under the simple loading with consideration for the effect of low temperatures on their structural state and mechanical properties.     

Mechanical properties of carbon nanotubes and their polymer nanocomposites

More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.     

泡沫金属多向承载行为的研究意义

泡沫金属具有优良的物理性能和综合力学性能,在很多场合都可用作轻质结构材料.在简要介绍该类材料用途的基础上,指出了多向载荷研究对于泡沫金属应用的实际意义,分析了以往工作在该类材料力学性能研究方面的不足,以期推进相关领域的研究者在该方面的突破.在此基础上,提出了一条研究该类材料在多向载荷作用下有关数理关系的思路.     

准晶材料的应用研究进展

就准晶材料作为表面改性材料和作为结构材料增强相两个方面，介绍了准晶材料在国内外应用研究的进展，强调了其特殊的性能在替代传统用材上的优势和应用潜力。     

The impact of powder diffraction on the structural characterization of organic crystalline materials

The bulk properties of organic crystalline materials depend on their molecular and crystal structures but, as many of these materials cannot be prepared in a suitable form for conventional single-crystal diffraction studies, structural characterization and rationalization of these properties must be obtained from powder diffraction data. The recent development of direct-space structure solution methods has enabled the study of a wide range of organic materials using powder diffraction data, many of structural complexity only made tractable by these advances in methodology. These direct-space methods are based on a number of global optimization techniques including Monte Carlo, simulated annealing, genetic algorithm and differential evolution approaches. In this article, the implementation and relative efficiency and reliability of these methods are discussed, and their impact on the structural study of organic materials is illustrated by examples of polymorphic systems, pharmaceutical, pigment and polypeptide structures and compounds used in the study of intermolecular networks.     

Elastic Gallium Phosphide Nanowire Optical Waveguides—Versatile Subwavelength Platform for Integrated Photonics

Emerging technologies for integrated optical circuits demand novel approaches and materials. This includes a search for nanoscale waveguides that should satisfy criteria of high optical density, small cross-section, technological feasibility and structural perfection. All these criteria are met with self-assembled gallium phosphide (GaP) epitaxial nanowires. In this work, the effects of the nanowire geometry on their waveguiding properties are studied both experimentally and numerically. Cut-off wavelength dependence on the nanowire diameter is analyzed to demonstrate the pathways for fabrication of low-loss and subwavelength cross-section waveguides for visible and near-infrared (IR) ranges. Probing the waveguides with a supercontinuum laser unveils the filtering properties of the nanowires due to their resonant action. The nanowires exhibit perfect elasticity allowing fabrication of curved waveguides. It is demonstrated that for the nanowire diameters exceeding the cut-off value, the bending does not sufficiently reduce the field confinement promoting applicability of the approach for the development of nanoscale waveguides with a preassigned geometry. Optical X-coupler made of two GaP nanowires allowing for spectral separation of the signal is fabricated. The results of this work open new ways for the utilization of GaP nanowires as elements of advanced photonic logic circuits and nanoscale interferometers.     

Ventilwerkstoffe für Verbrennungsmotoren

Valve Materials for Combustion Engines An overview is being given on production numbers, requirements and properties of valve materials. Their development from the beginning till today's state of the art is reviewed with a focus on Chromium-Manganese-Nitrogen-alloys. Valve materials are grouped by the criteria of density – heavy, lightweight – and alloying elements. The multiple stresses of the material in the valve are being met with a few standardised grades and specific ways of manufacture. The path of the material from bar stock to the finished valve is being followed. Engine development in the past decades increased the load on the valves which could be met by continuously developing their structural strength. Also the strength of all valve materials could be raised to nominal strength above 1100 Mpa by applying specific methods. Higher strength at the surface is being effectuated by work hardening effects. The technology to increase reliability of hollow valves and new aspects of valve seat facing including residual stress is explicitly discussed. General aspects of alloy utilisation is followed by a discussion of lightweight valve materials as Titanium alloys, intermetallic Titaniumaluminide alloys and ceramic materials, spec. Silicon Nitride, which all have a potential as forthcoming valve materials capable of reducing fuel consumption of the engines.     

Material Mechanical Properties Necessary for the Structural Intervention of Concrete Structures

Structural intervention involves the restoration and/or upgrading of the mechanical performances of structures. In addition to concrete and steel, which are typical materials for concrete structures, various fiber-reinforced polymers (FRPs), cementitious materials with fibers, polymers, and adhesives are often applied for structural intervention. In order to predict structural performance, it is necessary to develop a generic method that is applicable to not only to steel, but also to other materials. Such a generic model could provide information on the mechanical properties required to improve the structural performance. External bonding, which is a typical scheme for structural intervention, is not applied for new structures. It is necessary to clarify material properties and structural details in order to achieve better bonding strength at the interface between the substrate concrete and an externally bonded material. This paper presents the mechanical properties of substrate concrete and relevant intervention material for the following purposes: ① to achieve better shear strength and ultimate deformation of a member after structural intervention; and ② to achieve better debonding strength for external bonding. This paper concludes that some of the mechanical properties and structural details for intervention materials that are necessary for improvement in mechanical performance in structures with structural intervention are new, and differ from those of structures without intervention. For example, high strength and stiffness are important properties for materials in structures without structural intervention, whereas high fracturing strain and low stiffness are important properties for structural intervention materials.     

石墨烯及其衍生物掺配水泥基材料研究进展

石墨烯及其衍生物因其独特的结构及优异的性能在改善基水泥材料的抗拉强度、韧性、耐久性及赋予水泥基材料功能性等方面表现出良好的应用前景。本文简述了石墨烯、氧化石墨烯(GO)的结构特点及性能,归纳了各自的制备方法;对石墨烯及其衍生物在水泥基材料中的分散进行了综述;重点综述了石墨烯及其衍生物掺配水泥基材料的力学性能、流变性能、电学性能、热学性能、压敏性能等研究进展;分析了目前研究中存在的问题,并对研究趋势进行展望。      

The design of single crystal materials for magnetic bubble domain applications

The criteria for the existence of stable magnetic bubble domains and their potential in data storage applications are outlined. The development of single crystal materials capable of supporting such domains is reviewed. Particular emphasis is given to both the static and dynamic properties of bubble domains and to how, by careful materials design and preparation, the optimum balance of these properties can be attained.     

Fluoride glasses

A new family of vitreous materials based on the glass forming ability of some specific fluorides is presented. Conditions of formation, stability against devitrification, chemical durability, and structural models are examined in comparison with the traditional oxide glasses. The ZrF₄-based glasses and some other multicomponent materials are examined in depth in view of their promising optical properties, which arise from their broad transmission range from ultraviolet to mid infrared and their potential as ultratransparent materials for long distance repeaterless optical fibre. Other active optical applications of doped glasses, such as lasers and their electrical and magnetic properties, are also discussed.     

Structurally Controlled Cellular Architectures for High‐Performance Ultra‐Lightweight Materials

The design and synthesis of cellular structured materials are of both scientific and technological importance since they can impart remarkably improved material properties such as low density, high mechanical strength, and adjustable surface functionality compared to their bulk counterparts. Although reducing the density of porous structures would generally result in reductions in mechanical properties, this challenge can be addressed by introducing a structural hierarchy and using mechanically reinforced constituent materials. Thus, precise control over several design factors in structuring, including the type of constituent, symmetry of architectures, and dimension of the unit cells, is extremely important for maximizing the targeted performance. The feasibility of lightweight materials for advanced applications is broadly explored due to recent advances in synthetic approaches for different types of cellular architectures. Here, an overview of the development of lightweight cellular materials according to the structural interconnectivity and randomness of the internal pores is provided. Starting from a fundamental study on how material density is associated with mechanical performance, the resulting structural and mechanical properties of cellular materials are investigated for potential applications such as energy/mass absorption and electrical and thermal management. Finally, current challenges and perspectives on high‐performance ultra‐lightweight materials potentially implementable by well‐controlled cellular architectures are discussed.     

Progress in engineering high strain lead-free piezoelectric ceramics

Abstract

Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The ‘structural engineering’ approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications.     

Metal matrix composites. A bird’s eye view

Composite materials, in general, have so far been used mainly for structural applications. However, with regard to metal matrix composites, interest is growing on account of their physical properties. Indeed, customer requirements in this field cannot always be met by traditional materials. This paper first presents a brief overview of the interaction between fabrication, microstructure and properties of metal matrix composites. Further, some changes in the strategy for modelling and designing these materials are discussed. Finally, future prospects are outlined.     

Potentiality of utilising natural textile materials for engineering composites applications

This paper gives an overview of utilising natural textile materials as reinforcements for engineering composites applications. The definition and types of textile materials are addressed to provide readers a thoughtful view on the role of these materials in a structural composite system. Available material properties of natural textile and their composites are critically reviewed here. In general, these materials are categorised into fibre, yarn and fabric forms. The load bearing capacity of natural textile fibre reinforced polymer composites is governed by the quantity, alignment and dispersion properties of fibres. It has been found that the natural fibre reinforced composites are limited to use in low to medium load bearing applications. However, a limited research work has been performed to date and there is a significant gap between the high performance textile fabric and their use as reinforcement in fibre reinforced composite materials.     

Metamaterials: Reshape and Rethink

Metamaterials are composite materials whose material properties(acoustic, electrical, magnetic, or optical, etc.) are determined by their constitutive structural materials, especially the unit cells. The development of metamaterials continues to redefine the boundaries of materials science. In the field of electromagnetic research and beyond, these materials offer excellent design flexibility with their customized properties and their tunability under external stimuli. In this paper, we first provide a literature review of metamaterials with a focus on the technology and its evolution. We then discuss steps in the industrialization process and share our own experience.