54 research outputs found
Woodenboxspring â Schlaf in Harmonie mit der Natur
Le projet Ressobois a pour but de dĂ©velopper un systĂšme de ressorts en bois pour la literie afin de rĂ©pondre Ă la demande de la clientĂšle cherchant des lits 100% naturels. Au-delĂ du challenge fonctionnel, le projet ouvre de nouvelles portes sur la comprĂ©hension du comportement mĂ©canique du bois sous des sollicitations hygro-thermomĂ©caniques peu communes et explore des techniques dâusinage tridimensionnelles.Das Ziel des Projekts «Ressobois» ist es, eine Holzfederung fĂŒr Betten zu entwickeln. Damit soll das KundenbedĂŒrfnis nach Betten aus 100-prozentig natĂŒrlichen Materialen befriedigt werden. Neben der funktionellen Herausforderung eröffnet das Projekt neue Perspektiven fĂŒr das VerstĂ€ndnis des mechanischen Verhaltens von Holz unter nicht alltĂ€glichen hygro-thermomechanischen Belastungen und erforscht Techniken der dreidimensionalen maschinellen Bearbeitung
Natural and artificial ageing of spruce wood as observed by FTIR-ATR and UVRR spectroscopy
Spruce samples, naturally aged for 200, 400 and 500years, artificially aged by a hydrothermal treatment (at 180, 160 or 130°C, relative air humidities of 14%, 40%, or 60% and for treatment times between 1 to 50h), as well as reference samples, were analysed by Fourier transform infrared spectroscopy (FTIR) attenuated total reflection (FTIR-ATR) and ultraviolet resonance Raman (UVRR) spectroscopy. Natural ageing mostly affected the hemicelluloses and lignin, as observed from the FTIR-ATR and UVRR spectra, respectively. The UVRR spectra of the same samples after acetone extraction indicated that lignin was partially degraded and quinone structures were possibly formed. Artificial ageing at 160°C showed a significant change in the lignin structure, a well-known effect in the thermal treatment of wood, whereas treatment at 130°C did not alter the wood structure to any significant extent. Principal component analysis of the UVRR spectra confirmed that the spectra of artificially aged wood up to 160°C are dissimilar to naturally aged wood and which are also dissimilar to unaged woo
Edge and face linear vibration welding of wood panels
Edge-to-edge linear vibration welding of particle- board, OSB, MDF and plywood gives better strength than face-to-face panel welding. In general, the edge-to-edge weldline is slightly weaker than the panels itself. The face- to-face weldline is stronger than the strength of the material in the same direction
Parameters of wood welding: A study with infrared thermography
Welding of wood is a well-known joining procedure that offers several advantages over traditional mechanical fasteners or gluing. During welding, extensive solid-state transformation phases occur in the so-called melting zone and the heat-affected zone. The nature and the extension of such transformations are correlated to the energy input and thus to the heat generated during the process at the wood joint interface. In the present work the influence of the welding parameters and wood grain orientation on the temperature profile and distribution and final strength of welded connections was investigated. For this purpose, the characteristics of the joints were evaluated with both destructive and non-destructive techniques. Non-destructive evaluation was performed with infrared thermography, which allowed measurement of the maximal and average peak temperature, temperature profile and distribution, and rate of temperature increase. Thus, this technique can also be used to detect welding defects and to provide information on material modification during weldin
Parameters of wood welding: A study with infrared thermography
Welding of wood is a well-known joining procedure that offers several advantages over traditional mechanical fasteners or gluing. During welding, extensive solid-state transformation phases occur in the so-called melting zone and the heat-affected zone. The nature and the extension of such transformations are correlated to the energy input and thus to the heat generated during the process at the wood joint interface. In the present work the influence of the welding parameters and wood grain orientation on the temperature profile and distribution and final strength of welded connections was investigated. For this purpose, the characteristics of the joints were evaluated with both destructive and non-destructive techniques. Non-destructive evaluation was performed with infrared thermography, which allowed measurement of the maximal and average peak temperature, temperature profile and distribution, and rate of temperature increase. Thus, this technique can also be used to detect welding defects and to provide information on material modification during welding
Natural and artificial ageing of spruce wood as observed by FTIR-ATR and UVRR spectroscopy
Spruce samples, naturally aged for 200, 400 and 500 years, artificially aged by a hydrothermal treatment (at 180, 160 or 1308C, relative air humidities of 14%, 40%, or 60% and for treatment times between 1 to 50 h), as well as reference samples, were analysed by Fourier transform infrared spec- troscopy (FTIR) attenuated total reflection (FTIR-ATR) and ultraviolet resonance Raman (UVRR) spectroscopy. Natural ageing mostly affected the hemicelluloses and lignin, as observed from the FTIR-ATR and UVRR spectra, respec- tively. The UVRR spectra of the same samples after acetone extraction indicated that lignin was partially degraded and quinone structures were possibly formed. Artificial ageing at 1608C showed a significant change in the lignin structure, a well-known effect in the thermal treatment of wood, whereas treatment at 1308C did not alter the wood structure to any significant extent. Principal component analysis of the UVRR spectra confirmed that the spectra of artificially aged wood up to 1608C are dissimilar to naturally aged wood and which are also dissimilar to unaged wood
Beyond What Meets the Eye: Imaging and Imagining Wood MechanicalâStructural Properties
Abstract: Wood presents a hierarchical structure, containing features at all length scales: from the tracheids or vessels that make up its cellular structure, through to the microfibrils within the cell walls, down to the molecular architecture of the cellulose, lignin, and hemicelluloses that comprise its chemical makeup. This structure renders it with high mechanical (e.g., modulus and strength) and interesting physical (e.g., optical) properties. A better understanding of this structure, and how it plays a role in governing mechanical and other physical parameters, will help to better exploit this sustainable resource. Here, recent developments on the use of advanced imaging techniques for studying the structural properties of wood in relation to its mechanical properties are explored. The focus is on synchrotron nuclear magnetic resonance spectroscopy, Xâray diffraction, Xâray tomographical imaging, Raman and infrared spectroscopies, confocal microscopy, electron microscopy, and atomic force microscopy. Critical discussion on the role of imaging techniques and how fields are developing rapidly to incorporate both spatial and temporal ranges of analysis is presented
Natur beobachten und nachahmen
La nature est bien faite: le cĂšdre de Californie en est la preuve, il est le favori pour la fabrication des crayons depuis une centaine dâannĂ©es chez Caran dâAche. DâoĂč vient cette perfection? Comment obtenir ces qualitĂ©s sans devoir passer par les inconvĂ©nients de lâimportation dâune essence exotique?Die Natur kann es am besten, dafĂŒr ist Kalifornisches Zedernholz der Beweis. Seit hundert Jahren favorisiert Caran dâAche die Holzart in der Bleistiftherstellung. Woher kommt ihre Perfektion? Wie können wir diese QualitĂ€ten erreichen, ohne eine exotische Art importieren zu mĂŒssen
Soudage linéaire du bois : étude et compréhension des modifications physico-chimiques et développement d'une technologie d'assemblage innovante.
Wood welding by linear friction allows bonding of timber in a few seconds without unsing any adhesive. The adhesion is essentially due to the wood fibres entanglements which are embedded in a melted and recured intercellular polymers matrix. But the bonding interphase formation mecanism and the machine parameters and wood substrate influences are not clearly understood.Consenquetly, the goal of this study was to analyse the different factors which are influencing the joint characteristics in order to understand the physical and mecanical process mecanism. Infrared temperature measurements brought several informations on the process. On the other hand the welded joints were caracterized by microscopy, mechanical testing, fracture mechanics, interphase and smokes chemical analysis. The results were used to developp and to verify a physical and chemical scenario describing, in successiv steps, the interphase microstructure formation. A first numerical thermal model for Fagus sylvatica was build allowing the thermal simulation of the process.The aim of the last part of the study is the understanding of the wood substrate influences on the process. The variablity problematics like those due to wood species, wood anatomy or surface quality were investigated. Modified wood and wood panels were successfully welded.The research results were applied in the frame of a preindustrial development. This has reveal new scientific and technical problematics but also a great optimization capacity of this technology.Le soudage par friction linĂ©aire du bois permet de joindre deux piĂšces en bois en quelques secondes sans utiliser aucun adhĂ©sif. L'adhĂ©sion est essentiellement due Ă l'enchevĂȘtrement des fibres de bois bloquĂ©es dans une matrice de matĂ©riel inter-cellulaire fondu et re-durcit. Mais le mĂ©canisme de la formation de l'interface adhĂ©rente, l'influence des paramĂštres machine et de ceux du substrat sont peu connus. L'objectif de ce travail a donc Ă©tĂ© d'analyser les diffĂ©rents facteurs influençant les caractĂ©ristiques du joint pour comprendre les mĂ©canismes physiques et chimiques mis en jeu lors du processus. La mesure de la tempĂ©rature de soudage par thermographie infrarouge a apportĂ© de multiples informations. D'autre part les piĂšces de bois soudĂ©es ont Ă©tĂ© caractĂ©risĂ©es par des observations microscopiques, mĂ©caniques, une Ă©tude du comportement Ă la rupture, des analyses chimiques de l'interface et des fumĂ©es. Les rĂ©sultats ont permis d'Ă©laborer un scĂ©nario physico-chimique du dĂ©veloppement de la microstructure interfaciale et de le vĂ©rifier. Un premier modĂšle numĂ©rique thermique a Ă©tĂ© Ă©laborĂ© pour le soudage linĂ©aire de Fagus sylvatica. La derniĂšre partie de l'Ă©tude concerne la comprĂ©hension de l'influence du substrat. Ceci a permis d'aborder les problĂšmes de variabilitĂ© issus de l'essence de bois, de l'anatomie du bois ou encore de l'Ă©tat de surface. Les bois modifiĂ©s et des produits dĂ©rivĂ©s du bois ont pu ĂȘtre soudĂ©s avec succĂšs. Enfin les rĂ©sultats de la recherche on pu ĂȘtre mis en application Ă une Ă©chelle prĂ©-industrielle soulevant ainsi de nouvelles problĂ©matiques scientifiques et techniques mais aussi montrant un grand potentiel d'optimisation de la technologie
Potential Environmental Benefits of Ultralight Particleboards with Biobased Foam Cores
A new generation of ultralight particleboards (ULPB) with an expanded foam core layer produced in an in-line foaming step is under development. The environmental impacts of three types of ULPB containing foam based on 100% polylactic acid (PLA), 100% expanded polystyrene, and 50% PLA/50% polymethyl methacrylate, as well as a conventional particleboard (PB), have been compared in an LCA. Two approaches were chosen for the assessment: first, the âEPD-approachâ in accordance with EN 15804 for EPD of building materials and second, a holistic-approach which allows an expansion of the system boundaries in order to forecast the consequences of a broader replacement of PB with ULPB. The results show that most of the environmental impacts are related to raw materials and end-of-life stages. Both approaches show that the exchange of PB with ULPB with a foam core based on PLA leads to a reduction of greenhouse gas emissions. On the other hand, the PLA is responsible for higher ecotoxicity results in comparison to non-bio-based polymers mainly due to agricultural processes. Both approaches allowed the drafting of complementary advisories for environmental impact reduction addressed to the developers
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