Modeling the Influence of Knots on Douglas-Fir Veneer Fiber Orientation

This study presents a method for predicting the local fiber orientation of veneers made from peeled Douglas-fir logs based on the knowledge of the tree branch characteristics (location, radius, insertion angle, azimuth angle, and living branch ratio). This model is based on the Rankine oval theory approach and focuses on the local deviation of the fiber orientation in the vicinity of knots. The local fiber orientation was measured online during the peeling process with an in-house-developed scanner based on the tracheid effect. Two logs from the same tree were peeled, and their ribbons were scanned. The knot locations and fiber orientation were deduced from the scanner data. The first objective was to compare the fiber orientation model with measurements to enhance and validate the model for French Douglas-fir. The second objective was to link data measurable on logs to veneer quality.Région Bourgogne-Franche-Comté Ministère de l'Agriculture et de l'Alimentatio

Study on the in-process measurements of the surface roughness of Douglas fir green veneers with the use of laser profilometer

The presented research concerns the use of a laser proflometer to measure the surface roughness of green Douglas fir heartwood veneers during the peeling process. It investigates the effect of various process parameters on the surface quality. Three experiments were carried out with a single variable factor for each experiment: log centration, soaking temperature and cutting speed. Moreover, the origin of the surface roughness of Douglas fr green veneers was investigated. The study shows that laser proflometer seems to be a useful equipment in online measurement of surface roughness of green veneers. Based on the experiment results it was stated that surface roughness of Douglas fr veneers is characterized by large differentiation depending on the location on the veneer. The performed analysis shows that the surface roughness of Douglas fr green veneer could be improved when using relatively high cutting speed, not too high steaming temperature and logs with a centered core. The presented study shows that the laser proflometer can be effectively applied to the measurement and evaluation of green veneers during the peeling process and that there is still an area to develop this methodology.The authors gratefully acknowledge the financial support from the Bourgogne Franche-Comté region, the Ministère de l’Alimentation et de l’Agriculture Francais and the Xylomat Technical Platform from the Xylomat Scientific Network funded by ANR- 10-EQPX-16 XYLOFOREST. The study was done during Erasmus + internship for PhD students

Propriétés mécaniques en flexion de LVL de gros douglas

Selon un rapport rendu au Sénat le 26 juin 2019, le vieillissement du patrimoine des ponts du réseau routier est un problème à traiter en France. Le remplacement progressif d’environ 10% de ces ouvrages est à envisager dès à présent. Une des solutions proposées à la région Bourgogne-Franche-Comté est l’élaboration de ponts mixtes bois béton. Efficaces, comparativement plus légers, rapides de mise en œuvre, plus écologiques et économiques, ils permettent par ailleurs la valorisation d’essences locales dans des qualités relativement basses. Cela est rendu possible par le choix d’un procédé de première transformation, le déroulage, permettant la composition d’un matériau multiplis composite appelé lamibois, au comportement mécanique augmenté par rapport au bois massif dont il est issu. La thèse « Développement de produits lamellés issus du déroulage de douglas pour des ponts et autres solutions constructives mixtes bois-béton collés », effectuée au LaBoMaP de Cluny, vise à optimiser ce matériau dans la conception des poutres de tablier. Cela passe notamment par une répartition optimisée dans tout le matériau des défauts tels que la nodosité et la variation de pentes de fils. Cependant, avant toute étape d’optimisation, il est nécessaire d’étudier le comportement mécanique du LVL sans plis croisés constitué à partir d’une ressource représentative du douglas français (100 m3 de bois transformés issus de 3 communes de Corrèze : Larfeuil, Ambrugeat et Neuvic d’Ussel). Il n’y avait jusqu’alors pas d’étude d’ampleur sur le LVL issu de cette ressource. Certains résultats ont été présentés aux assises France Douglas. Ce court article présente les premiers résultats d’essais de flexion quatre points sur chant de poutres de duramen de douglas selon deux configurations géométriques. Seule la configuration sur chant est testée car elle est la configuration préférée dans son intégration par poutre à une structure pont

A simple method to determine the diffusivity of green wood

Log temperature appreciably influences veneer quality during the rotary peeling process. The assessment of the thermal properties of green wood is complex and typically requires the sawing of small calibrated samples. This study introduced a simple approach based on an inverse identification method to determine the global log thermal diffusivity online and without the time-consuming extraction of wooden samples that is commonly used to perform diffusivity experiments. This method was applied to green Douglas fir logs and resulted in an average thermal diffusivity of 0.175 ± 0.021 mm2.s-1. This method was found to be suitable for both heartwood and sapwood and thus can provide a globally applicable diffusivity assessment method. This global parameter is essential to optimizing the soaking time and improving the subsequent veneer production quality. As log-soaking preprocessing requires an immense input of energy, this time-optimization strategy will allow sizable cost reduction and ecological improvement.Région Bourgogne-Franche-Comté Ministère de l'Agriculture et de l'Alimentatio

An insight into mechanical properties of heartwood and sapwood of large French Douglas-fir LVL

The French resource of large diameter Douglas fir is currently still growing, while these large diameter trees are complicated to process efficiently by the sawmilling industry. The rotary peeling process appeared to be particularly adapted as an alternative to the usual sawing. This primary processing method produces veneers used to make a wood engineered product material called Laminated Veneer Lumber (LVL). The manufacturing process of LVL enables the distribution of the resource defects, allowing for increased mechanical behaviour compared to the solid wood from which it comes from. The main objective of this study is to provide an insight into the principal Douglas-fir heartwood LVL mechanical properties such as longitudinal and shear moduli of elasticity, bending, shear and compressive strengths. Up to now, there was no study on LVL derived from this resource. This study focuses on heartwood because of its very interesting natural durability properties for constructive outdoor applications. Moreover, a comparison with structural timber properties and a comparable industrial engineering product, made of Norway spruce and called Kerto© S was also achieved to place the material in terms of mechanical performance among the market. Globally, this Douglas-fir heartwood LVL showed high compressive and shear properties. Even though the bending properties were significantly lower than data from Douglas-fir LVL of the literature, they seemed appropriate for structural applications. A larger experimental campaign fully representative of the industrial process and dealing with larger samples will be needed to finally conclude on the characteristic values to be used in structural design. © 202

Bending, shearing, and compression properties of fast growing French Douglas fir LVL

The French resource of large diameter Douglas fir is currently keeping growing, while these large diameter trees are complicated to process efficiently by the sawmilling industry. The rotary peeling process appeared to be particularly adapted as an alternative to the usual sawing. This primary processing method produces veneers used to make a wood engineering product material called Laminated Veneer Lumber (LVL). The manufacturing process of LVL enables the distribution of the resource defects, allowing for increased mechanical behaviour compared to the solid wood from which it comes from. The main objective of this study is to present the principal Douglas-fir heartwood LVL mechanical properties such as longitudinal and shear moduli of elasticity, bending, shear and compressive strengths. Up to now, there were no study on LVL derived from this resource. This study focuses on heartwood because of its very interesting natural durability properties for constructive outdoor applications. Moreover, a comparison with structural timber properties was also achieved to place the material in terms of mechanical performance among the market. Globally, this LVL material showed high compressive and shear properties. Nevertheless, even though the bending properties were significantly lower than data from Douglas-fir LVL literature, they are still quite acceptable for structural applications. © WCTE 2021. All rights reserved