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The springback effect in molded wood laminations within the elastic range has, to date, not yet been mathematically described. Once cured, residual internal stresses within the laminations cause the final form to deviate from that of the die. Test pieces of beech laminations of 1 mm, 2 mm and 4 mm thicknesses and stack sizes of between 2 and 16 laminations were used. The elasticity value of each stack was obtained using non-glued laminations in a three-point bending test within the elastic region. The laminations were glued with polyurethane resin and mounted in a radius form die. The stress induced by the die onto the stack is within the elastic region of the material without any prior chemical or physical plasticisation of the wood. After curing was complete and the laminations removed from the die, the actual radius was calculated using a circular equation within the CAD program, using three measurement points taken from the stack. The radius of the die within the limits of this study has a negligible effect when predicting the springback of the stack. The exponential correlation between springback and the number of laminations, was used to calculate the springback effect on molded laminated stacks.
In recent years, a large number of different studies have shown that a variety of positive property changes can be achieved by thermally treating spruce resonance wood. Various methods have been established, which differ mainly in the choice of treatment atmosphere, but also in the associated treatment duration and temperature. Part of the present investigation was to compare a thermal-vacuum process with a process which takes place in an oxygen-reduced atmosphere, with regard to various property changes. The results show that both processes achieved similar results in terms of dynamic acoustic property changes. Larger differences were found with regard to moisture behavior and color change.
To this day, many guitar makers around the world use primarily tropical woods such as rosewood (Dalbergia spp.) for their production. Due to the current CITES regulation of January 2017 regarding the trade of tropical woods, it becomes inevitable to generate alternative materials with similar material properties to be generated and established. Part of this study is an acoustic comparison of two guitars. One made of untreated tropical wood [Dalbergia nigra Benth.)] and one made of European thermally modified wood (TMT) species. [Pyrus (L.) and Alnus (Mill.)]. The method used allows a significant statement about the acoustic radiation performance of stringed and plucked instruments. The experimental setup consists of an impulse hammer for excitation of a force in the center of the bridge and a microphone for recording the signal radiated by the guitar body at a distance of one meter from the sound hole. A front-end was used to record the data, and further processing was done using analysis software to determine frequency response functions (FRFs) of the two instruments. The FRFs determined can be subdivided into several ranges which contain the different acoustic information about bass range, loudness, clarity, brightness and sharpness of the instruments. Examination of the frequency ranges reveals an acoustic similarity between the two guitars. Slight differences can be seen in the bass and loudness areas, where the guitar from TMT has a higher average level. Clearer differences are offered by the areas of clarity, where the guitar made of tropical wood shows a higher average level. In summary, the method gives an efficient acoustic impression as a function of the natural frequencies of the two guitars. The measured data show similarities and thus comparable acoustic properties of the instruments. However, additional effects such as psychoacoustic sensations or musical taste for the complete acoustic impression of an instrument are also of importance. Therefore, further empirical and fundamental research is needed to obtain a more detailed acoustic impression of the instruments.
In the field of instrument making, the use of indigenous wood species is becoming more and more important due to the increasing environmental awareness of instrument makers and their customers. As the properties of some of these wood species cannot meet the high demands of this field of application, processes are being sought that can achieve improvements. In recent years, many studies have shown that different modification methods, such as furfurylation, thermal treatment, densification or impregnation methods, can partly improve wood properties such as elasticity, strength values, damping behaviour, but also moisture behaviour and wood moisture content significantly. The extent to which different modification processes and their positive changes in properties can be combined with each other and thus achieve further improvements will become increasingly important in the future, not only in instrument making but also in other areas of application. Therefore, this study investigated the influence of thermal treatment followed by linseed oil impregnation of wood on its sound propagation velocity and the associated acoustic properties of characteristic impedance and acoustic radiation.
The thermal modification of wood is considered to be an environmentally friendly and cost-effective treatment process, which has been able to establish itself in many areas of application due to its positive effect on a whole range of different material properties through a wide variety of process designs. In addition to heat transfer and pressure, closed and open systems differ primarily in the choice of treatment atmosphere mainly used to prevent combustion (Sandberg et al. 2021). Although many studies in recent years have investigated influencing process parameters such as temperature, pressure or treatment duration, there exists a knowledge gap regarding the influence of the treatment atmosphere or its behaviour during the treatment process (Candelier et al. 2016). Therefore, this study aims to analyse different oxygen-nitrogen concentrations in the treatment atmosphere at different residual oxygen levels during the process duration and their influence on different property parameters of Fagus sylvatica (L.).
Different parts of the guitar body are made of certain wood species, selected by their specific properties. The sound board, which is mainly made of spruce or cedar, transfers the vibration of the strings to the resonance body by means of the bridge. The sides and the back of the guitar rather reflect the sound of the acoustic vibrations and are predominantly made of tropical hardwoods like palisander, mahogany or ebony species. These species have limited availability and are listed on the CITES Annex I and II. To substitute tropical wood species, thermally modified European wood species with improved acoustic properties and dimensional stability may be used. Although the acoustic reflection of the sides and the back parts of a guitar body is an important property, there is not much knowledge about this reflection behaviour of wood. A few studies like the work of Hong (1989), Kang (2010) or Smardzewski et al. (2013) investigated the sound absorption properties of unmodified wood. Subsequently this study considers the sound absorption coefficients of unmodified and thermally modified European wood species in comparison to an unmodified tropical wood species.
Aufgrund von Rohstoffknappheit auch bei nachwachsenden Rohstoffen kann das Recyceln von Holz und Holzwerkstoffen auch im Möbelsektor nur an vorletzter Stelle, vor der thermischen Verwertung, stehen. Davor gilt es, schon bei der Produktion den Materialeinsatz zu reduzieren bzw. Möbel so zu gestalten, dass eine verlängerte Nutzung möglich ist. Insgesamt muss die Produktnutzung intensiviert werden. Dafür sind unter anderem geeignete Businessmodelle erforderlich. Hiermit beschäftigt sich das Projekt PERMA an der HNEE. Wird Holz dann zum Altholz, muss die Nachnutzungsquote deutlich erhöht werden. Mit der Identifizierung und Indexierung von Altholz befasst sich daher das Kooperations-projekt WIn-Altholz. Sind allerdings Holzspan- und Holzfaserwerkstoffe beschä-digt oder werden nicht mehr benötigt, gibt es bisher keine sinnvollen Nachnut-zungsszenarien. Das Forschungsprojekt „Respan“ will nun ein Recyclingverfahren entwickeln, dass die Nachnutzung möglichst aller Bestandteile der Werkstoffe realisiert.
The aim of this study is to investigate the mechanical properties and structural changes of wood during long-term tempering in mild temperatures. As a result of a long-term heat treatment on beech wood (Fagus sylvatica L), the degradation or decomposition reaction of wood-bound cellulose, hemicellulose and lignins in the low temperature range up to 150°C investigated. For this purpose, test series in the dry state are thermally treated over a period of 6 weeks at a temperature of 120°C and 140°C. Weekly, the mass and dimensions of the test specimens are recorded in order to effectively track the density curve. The mechanical
resistance of the wood substrate was realized by a hardness measurement in a weekly period.
Impregnation of wood with certain chemical compounds is a well established method to improve its physical and mechanical properties.
However, the result is often not quite homogeneous. This study examines the effect of two varying thermal treatments on the impregnability of sycamore maple (Acer Pseudoplatanus L.) with furfuryl alcohol (FA), and on the resulting Anti-Swelling-Efficiency (ASE).
This is a data management plan for the DFG research project "Predictability of color changes of wood used indoor - A new approach to evaluate the color change as a function of the radiation dose". DFG Funding code / Project number: 442135169
Project website: https://gepris.dfg.de/gepris/projekt/442135169?language=en
This data management plan (DMP) applies to the Research Data Management Organizer (RDMO) questionnaire and was operated with the RDMO software: https://rdmorganiser.github.io/en/
Academic data stewardship at universities has to fulfil many different roles. One of the most important is to build up a connection to researchers and bridge the gap between research data infrastructure and researchers. Different scientific communities have different requirements for research data management and expectations regarding text and data publication. In many of the sub-disciplines of engineering sciences, research data management practices are not established so far. When it comes to contact between data stewards and researchers, a common knowledge base has to be established to become clear about why and what actions for research data management has to take, that engineering researchers can adapt them for their research data management practices. Many research data management standards have to take into consideration. However, to this point of time, the research data management community lacks for data literacy graphics to explain how the technical data management ecosystem works together with standards like the findability, accessibility, interoperability and reuse (FAIR) principles. Therefore, we developed a graphic for data literacy and consulting scenarios.
The background of the topic is to compare the colour changes at different irradiances and temperatures at constant relative humidity. The issue is important because evaluation in terms of irradiance has not been studied in more detail. Irradiation intensities were reported in many studies but tended to have metadata status. The concrete influence of the irradiance on chemical and colour changes in the wood remains open. This paper presents an approach to inquiry-based teaching within a basic research project. Initial results from a large-scale data series are presented here. Irradiance is the term for the total power of incoming electromagnetic energy striking a surface, related to the size of the area, measured in watts per square metre [W/m²].
Similar to a normal wave, a shock wave travels as energy through matter but it causes an abrupt raise of pressure, temperature and density. In this study the influence of shock waves on wood structure were investigated in the light of possible future industrial utilization e.g. timber impregnating treatment.
Diese Handreichung knüpft an diese Fragen an: Sie zeigt auf, wie durch Nachhaltigkeitstransfer Lehr-Lern-Prozesse in lebensweltliche Kontexte eingebettet werden können. Transfer findet unserer Erfahrung nach bereits in vielfältiger Form Eingang in die Lehre. Aber häufig fehlen Zeit, Ressourcen und Ansatzpunkte, um Transfer systematisch zu planen, umzusetzen und ihn so zu gestalten, dass er zu nachhaltiger Entwicklung beitragen kann.
Wood and wood-based products are widely used for structural building elements, but due to their composition, they are susceptible of combusting if exposed to fire. Fire safety is an important issue of building safety, especially when the building's fire load contents enhance the risks of fire spread. Therefore, the involved materials are very important to address the fire safety requirements. When existing timber structures are involved, the most usual way to improve its reaction to fire is to treat wood with fire retardant materials.
The idea of this paper is to give an overall overview, on the existing fire-retardant and intumescent coating materials, modification, and treatments that can be applied to wood and wood-based products in order to improve their reaction to fire.
Similar to a normal wave, a shock wave travels as energy through matter but it causes an abrupt rise of pressure, temperature and density. In this study, the influence of shock waves on wood structure were investigated in the light of possible future industrial utilization e.g. timber impregnating treatment. The constructed autoclave is capable of creating shock waves either by an electrical pulse breakdown of a spark gap arrangement or by electromagnetic actuators. The penetration depths of the fir wood test samples were measured using light microscopy, SEM and micro-computed tomography. Our results showed that by varying the intensity of the incident shock wave, the distance between the shock wave generating device and the test sample, and/or the orientation of test sample in relation to the shockwave, the wood tissue structure had been heavily disintegrated or hardly affected at all. An improvement on impregnation could not be found.
Im Rahmen des Forschungsprojektes PyroForCE wurde untersucht, inwieweit sich das Brandverhalten von Fassadenhölzern alleine durch die Erzeugung einer oberflächlichen Pyrolyseschicht so verändern lässt, dass dadurch die Anforderungen für eine Klassifizierung als schwerentflammbarer Baustoff dauerhaft erfüllt werden. Hierzu wurde eine kontinuierlich arbeitende Holzpyrolyseanlage entwickelt, mit der reproduzierbare Pyrolyseflächen auf Prüfkörpern der Holzarten Eiche, Lärche und Fichte erzeugt werden konnten. Durch eine zusätzliche Stabilisierung mit Natriumwasserglas lassen sich sowohl die oberflächliche Abriebfestigkeit erhöhen als auch die Brandschutzwirkung verbessern. So modifizierte Fassadenhölzer können im Single-Burn-Item-Test eine Klassifikatione als "schwerentflammbares" Bauprodukt erreichen. Damit ist das Ziel erreicht, nur durch Oberflächenpyrolyse in VErbindung mit einer Stabilisierung durch rein mineralische Wassergläser das Brandverhalten von Fassadenhölzern so zu verändern, dass eine Zuordnung zu den schwerentflammbaren Baustoffen erreicht werden kann und diese damit als Fassadenmaterial im städtischen Kontext und der Gebäudeklasse 4 und 5 einsetzt werden dürfen.
Einfluss der Schlichte von Celluloseregeneratsfasern auf die Zugscherfestigkeit bei Holzverklebungen
(2020)
Es wurden Längszugscherversuch an mit Celluloseregenaratfaser (CRF) verstärktem Epoxidharz durchgeführt. Dabei wurden die Festigkeiten von CRF mit und ohne Schlichtemittel verglichen. Die dauerhafte Ausbildung eines stabilen Verbundes zwischen CRF und Epoxidharz ist weiterhin problematisch. Der Einsatz eines Schlichtemittels wirkt sich nicht auf die Verklebbarkeit der Fasern in der Matrix aus. Sowohl die Werte des Zugscherversuchs als auch die makroskopischen Bruchbilder und die mikroskopischen Analysen von Rissen in der Matrix zeigen keine nennenswerten Unterschiede zwischen beiden untersuchten Varianten.