Papers by Keyword: Lightweight Structures

Abstract: Due to the additive manufacturing process concept - layered synthesis of products, it becomes necessary to apply new approaches to the design of parts. One of the main tools that need to operate is numerical simulation, capable, with a skilful approach, to give an engineer an integrated procedure to the development of new products. Numerical modeling, in addition to carrying out strength calculations, includes topology optimization and the creation of lattice structures, through which it is possible to create lightweight products. New design meets requirements of strength characteristics. The use of this tool leads to a reduction in the amount of initial material and as a result - cost saving. In this paper, using the bracket as an example, was used the topology optimization method with subsequent redesign. The paper presents the results of calculations of the stress-strain state of the initial and final structures, allowing estimating the possible reduction in the mass of the product and the amount of consumable material in the manufacture of additive technologies.

Abstract: The manufacturing of high load components in automotive and mechanical engineering demands for an increased usage of combined plastics processing procedures. In practice, full plastic hybrid components are produced in a series of individual processes such as thermoforming or injection molding. The constructive implementation has often only material-substituting character wherein the high potential for lightweight anisotropic fiber composites is exploited only to a limited extent. Based on the application of a coupling brace in a vehicle, a new component design for function-integrated interface elements is enabled by an integrated injection molding technology. The targeted transfer of high local stresses by load-bearing insert elements regarding contoured metal sheets or Fiber Reinforced Thermoplastic Composites (TP-FRC) semi-finished products with endless fiber reinforcement enables efficient dimensioning of components. This fusion of technologies to a Multi Material Design (MMD) form the basis for novel weight-optimized, as well as cost-effective applications and lead to a high bending stiffness and high strength of structures. The composite strength of MMD components is increased by a variation and optimization of the thermoplastic/TP-FRC respectively thermoplastic/metal-interfaces. This objective will be achieved by highly efficient and integrated process flows and by the new entire construction of the component.

Abstract: Currently there is a great demand for energy and resource efficient and also function integrating manufacturing processes. Therefore, suitable technologies and corresponding foundational researches are being pursued in the federal cluster of excellence “MERGE Technologies for Multifunctional Lightweight Structures” at the Technische Universität Chemnitz. A part of this project is the development of the continuous orbital winding (COW) technology including the goal of a large-scale process used for special fiber-reinforced thermoplastic semi-finished products. This method is an inverted winding process. The winding core needs to perform only the feed motion. Furthermore, this allows synchronization to upstream and downstream process chains.Due to the modular structure of the machine concept, it is possible to integrate a sensor system during production without interrupting the process. For this purpose, a textile carrier tape with integrated electrically conductive fibers and applied sensors is embedded. Various silicon sensors, e.g. acceleration, pressure or stress sensors are applied by micro-injection molding. A so-called “interposer” is used as an electrically adapter between the microstructures of the sensor system and the mesostructures of the textile.In this article, basic investigations for the continuous processing of semi-finished thermoplastic structures and the integration of sensors are presented. It is intended to determine the bonding properties, possible structural thickening by the sensors and the resistance of the sensor systems and its electronic components to the process conditions.In summary, investigations are carried out to determine the parameters of the machine system as well as to determine the optimum processing conditions for the application of additional elements.

Abstract: Sandwich foam beams, made of solid skins and aluminium foam core, are usually applied in high-tech engineering field while they are not yet adopted in civil structures. An initial, explorative study on the structural application of metal foam is presented in this paper. The potentials of sandwich foam beams are studied through analytical models and parametric analyses; the sensitivity of the flexural response of the media to the total amount of pores and their spatial distribution are investigated. An analytical tool able to design functionally graded beams of metallic foam is presented and applied with reference some commercial aluminium foams. An experimental campaign is being planned to validate the presented results.

Abstract: Aim of this paper is to show modern lightweight structures based on tensegrity systems. Principles of tensegrity structures and cable domes are shown. Last part of this paper is demonstrated how to join simple tensegrity prisms to tensegrity slabs. These structures are very interesting from architectonical point of view, they are made from fully recyclable material – steel and consumption of material is very low. Tensegrity structures have a great potential of the development of modern civil engineering.

Abstract: In recent years fibre-reinforced polymers (FRPs) gained importance in a wider field of application due to such favourable properties as low mass and tailorable mechanical strength. However, water penetrating into the lightweight material can lead to a loss of shear strength and finally to a collapse of the whole mechanical structure. Consequently, the integration of humidity sensors into compound materials is able to promote the reliability via online condition monitoring. An innovative concept is the use of ceramics-polymer-composites, which are well suited for the integration into lightweight structures during inline production. Composite and polyimide based humidity sensors have been manufactured by flexographic printing and spin-coating processes. A 5-fold increase in sensor’s capacity related to a humidity change from 10 to 80 % r.h. manifests the outstanding sensitivity of manufactured composite sensors. In addition, FRP-integrated polyimide sensors showed a significant response to water penetration, whereby the capability of condition monitoring could be confirmed.

Abstract: Classical lightweight construction in the field of machine tools is reaching its limits. New materials like fibre reinforced plastics are not widely used yet. The main reasons are the high material and production costs. This paper presents an approach for substituting a conventional component of the machine tool’s periphery by a structure made of fibre reinforced plastics. An easy and economic production process was used to enable quick fabrication.

Abstract: This article aims to disclose some aspects of the research and constructive methods on lightweight structures made of tied-up bamboos developed by the Laboratory for Investigation in Living Design, LILD, from PUC-Rio. In this paper, we demonstrate the way of obtaining a shape similar to the one of a soap bubble when blown and manipulated by the researcher, according to previously established parameters. The approximation of such a geometry is achieved through a variety of interactive experiments between the states of a model electronic, manufactured /miniature, and in use that follow the logics of geodesic lines, obtained by means of a grid when inflated. Finally, we present results of initial observations of the assemblage of the bamboo reticular structure in the in use state, that we call The Bubble Hall.

Abstract: In this work, an attempt has been made to improve the mechanical strength of 6063 aluminium alloy and thus its lightness via combination of severe plastic deformation (grain size refinement) and heat treatment (precipitation hardening). 6063 aluminium alloy was chosen as the best material for lightweight structures, where mass reduction is important, because of its high extrudability. Samples were hydrostatically extruded (HE) in supersaturated condition and subsequently subjected to an aging process. HE brings about significant grain size refinement well below 1 micron. The influence of aging parameters such as time and temperature on mechanical properties evolution of extruded material was determined. The microstructure of ultrafine grained (UFG) alloy was investigated using transmission electron microscopy. The average grain diameter and grain boundary misorientation angles (using Kikuchi lines) were measured. Mechanical properties were examined in microhardness and tensile tests. The results have shown that it is possible to combine grain boundary and precipitation strengthening and obtain ultrahigh strength in 6xxx series alloys. Additionally, heat treatment of UFG samples causes an increase in ductility measured in tensile tests, which is rather poor in severely deformed materials. To prove advantages of UFG aged samples for lightweight applications, finite element modelling was performed to compare the mass of chair elements made of coarse and ultrafine grained material. Simulations were made for the same stresses applied. It has been shown that if the chair was made of UFG aluminium alloy the mass reduction would be approximately 30 %.

Abstract: This article aims to disclose the developments of a research on constructive methods of lightweight structures, developed by the Laboratory for Research on Living Design, LILD, from Pontifical Universidade Catolica do Rio de Janeiro, PUC-Rio. One of the objectives of this paper is, using principles of biomimesis, to systematize constructive processes by means of the understanding of how nature creates its forms. In the Laboratory, experiments with soap bubbles and catenaries have been serving this purpose In this case, studies resulted in the solution to the covering of the newly constructed LILDs building, located in the campus of the University, a textile-architecture where structural elements and joints, usually made of steel or wood, were replaced by bamboo culms tied together. The present article also demonstrates how these culms were benefited in order to meet specific requirements of the project.