| 1. |
- Báder, Mátyás, et al.
(författare)
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Wood densification processing for newly engineered materials
- 2018
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Ingår i: Proceedings of the 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), Freising/Münich, September 20-21. - Kuchl. ; , s. 255-263
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Konferensbidrag (refereegranskat)abstract
- Wood is a renewable, bio-based material with a mixture of different properties and qualities, used in numerous applications. Beside many species with high wood qualities several species suffer due to a number of disadvantages, where low hardness and abrasive resistance are characteristic for low-density species. This paper presents examples of on-going European research projects and industrial processes mostly related to wood densification methods. Wood densification is a classical thermohydro-mechanical (THM) wood treatment process, through which density is increased by mechanical compression of wood perpendicular to the grain, by impregnation of cell lumens or cell walls with solutions or melted substances (resins, waxes), or by a combination of both. The purpose is to produce newly designed and engineered materials and products with new property profiles, which would potentially find new markets. In general, the THM processes consist of three stages: plasticization of the wood cells, followed by the actualcompression, and finally solidification of the compressed wood in order to prevent elastic spring-back and the moisture-induced set-recovery. The wood densification process refers but is not limited to solid wood and might apply to whole wood pieces, or to local areas within given pieces only. Another THM method is the mechanical compression of wood parallel to the grain, which leads to a product with high flexibility. A European wood research network, represented by the authors of this contribution, has extended experience in many wood modification processes, as demonstrated through ongoing researches and case studies in this paper
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| 2. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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Temporary buildings in reusable lightweight material design
- 2016
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Ingår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE). - Vienna : Vienna University of Technology.
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Konferensbidrag (refereegranskat)abstract
- There is a growing need and market for temporary buildings for various purposes, including largeconstruction projects in the tourism and events sectors or in civil protection. This paper gives an overview about the useof reusable lightweight materials in temporary buildings. Based on a project proposal submitted to the 7th framework, anew concept of temporary buildings is proposed. This concept combines the advantages of the premanufacturing of asmall number of parts and wooden components and a flexible and modular erection of the temporary building. Thefocus is on fast establishment with a maximum of three persons. A flexible and modular extension is possible.Assembling and disassembling the individual components with novel connect systems, adapted from the furnitureindustry, is proposed.This project aims to bring these concepts into new temporary buildings with new, reusable, and flexible lightweightdesign.
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| 3. |
- Grubîi, Victor, 1990-
(författare)
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Quality Aspects of Sliced Oak Lamellae in Development of Engineered Wood Flooring
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Valuable hardwoods, such as oak, although renewable, present limitations in product realisation in terms of their cost and availability, often attributed to production waste and sub-optimal product design factors. The slicing technique facilitates the production of thin wood lamellae, minimising waste and ensuring optimal material conversion. This study explores the application of sliced lamellae in engineered wood flooring, focusing on quality aspects and control. The performance of sliced lamella-based engineered flooring was compared with traditional parquet flooring elements through standard performance tests, which scrutinised the characteristics of appearance, delamination, and dimensional stability under varying climate conditions. The climate tests highlighted the significant flaws of sliced lamella-based flooring elements: surface-checking. Despite diminished delamination resistance, the dimensional stability excelled for the sliced lamella–based flooring. Primary observations indicated that the study’s constraints are related to a lack of surface-checking quantitative measurements and an absence of sliced lamellae quality control. The subsequent research characterised sliced lamellae quality using the properties of slicing checks and mechanical performance perpendicular to the grain. Slicing thickness is considered a critical variable in both lamella-processing and product performance factors. A detection method using image processing and analysis was developed to characterise slicing check occurrence. The method considered slicing check characteristics, check depth ratio and check frequency. The results of the slicing check inspection indicated a decrease in the check depth ratio and check frequency with increased slicing thickness. Mechanical testing revealed that oak sliced lamellae exhibited considerably lower strength and stiffness compared to sawn solid wood. The slicing check depth ratio was found to be negatively correlated with the sliced lamellae’s tensile strength and strain at break.A novel method for detecting surface-checking was developed and employed. It utilised digital image correlation and analysis of full-field strain data. The novelty of the method is advancing the surface-checking quality index that considers the check length over the inspected area. This method was applied to engineered wood flooring to evaluate the impacts of core type and sliced lamellae nominal thickness on surface-checking results. Significant interactions between the studied variables were found, indicating that the surface-checking tendency could not be attributed to a single factor. Especially notable was the reduced surface-checking outcome in standard core specimens paired with a low lamella thickness. This thesis offers new insights into using sliced lamella in engineered wood flooring realisation. Although the assumed sliced lamellae quality aspects, slicing check depth and check frequency, were shown not to impact surface-checking, the significant interactions between engineered wood flooring construction parameters highlight the need for a broader perspective concerning this subject. Future research should focus on further refining the sliced lamellae quality analysis and developing new methods that consider other quality aspects.
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| 4. |
- Neyses, Benedikt, 1986-
(författare)
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Surface Densification of Solid Wood : Paving the Way Towards Industrial Implementation
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface densification of a piece of solid wood results in an increase in density and in hardness in the whole or a part of the densified material, and is one of the ways of improving the properties and value of low-density wood species. Despite efforts for many years, mass commercialisation of either bulk- or surface-densified wood products has not yet been achieved. Most of the previously tested densification methods have limitations in terms of processing speed and integration into the largely continuous wood processing chain, which leads to high production costs. Established methods to eliminate the set-recovery rely either on technologically complex close-system methods or on open-system methods that require relatively long periods of high energy input. For this reason, impregnation with adhesives is used in almost all commercially available densified wood products, and none of them have risen above their status of being niche products.Based on this background, three objectives for this project were formulated: (1) the development of a method for selecting the most suitable wood species for surface densification, (2) showing that surface densification can be carried out in a continuous manner at high process speeds, (3) and researching a fast open-system method to reduce the set- recovery.The method developed for selecting the most suitable wood species for surface densification was based on Lean principles, and it confirmed the suitability of previously studied wood species, such as Scots pine, spruce and poplar. In addition, several suitable alternatives from different parts of the world and from different types of forest were identified. This suggests a high potential for establishing such wood products on a global market level.Two studies using a continuous roller press showed that solid wood can be successfully surface-densified at process speeds of up to 80 m min-1, and that some defects, such as knots, are acceptable in the raw material, but the problem of set-recovery could not however be solved.A screening experiment testing different open-system approaches to reduce the set-recovery highlighted the potential of a novel method using ionic liquids as a plasticiser prior to the surface densification of solid Scots pine. The set-recovery could be reduced to 10%, with the time of high energy input being less than 10 minutes. The Brinell hardness was increased by a factor of 2.7 over that of undensified wood. A study with thermo-gravimetric analysis and digital image correlation showed that the set-recovery almost exclusively happens in the transition zone between the densified and undensified wood cells, where there is less penetration of the ionic liquids.The work accomplished in this project has successfully addressed several gaps in the field of wood densification, firstly, by employing a continuous surface densification process using a roller press, and secondly, by developing and studying a fast open-system pre-treatment with ionic liquids, which greatly reduces the set-recovery. Research will continue on a new band press, facilitating a swift transfer of knowledge between small- scale studies and the continuous surface densification of production-size wooden boards.
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| 5. |
- Rademacher, Peter, et al.
(författare)
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European co-operation in wood research From native wood to engineered materials : Part 3: engineered hybrid wood-based products
- 2017
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Ingår i: Pro Ligno. - Romania : Pro Ligno Foundation. - 1841-4737 .- 2069-7430. ; 13:4, s. 361-372
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Tidskriftsartikel (refereegranskat)abstract
- Forest-based industries have been continuously developing advanced processes, materials and wood-based solutions, to meet evolving demands and increase competitiveness. Engineered wood products (EWPs) constitute one emerging group of materials aiming at improved property profiles of wood, and provide desired shapes and functionality. In this paper, the main principles for different processes to soften wood and make it more flexible for bending and moulding, such as longitudinal compression, plasticization by water vapour and gaseous ammonia, and a dielectric heating technique, are discussed. Examples of implementation of these techniques for the production of wooden products are presented, and the use of reed canary grass, and a novel technique for embossment of hybrid particleboards are also further discussed.
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