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Développement de produits LVL de douglas aux propriétés mécaniques optimisées par l’exploitation de la mesure en ligne de l’orientation des fibres lors du déroulage

Abstract : Abstract: The grading of wood veneers according to their true mechanical potential is an importantissue in the peeling industry. Unlike in the sawmilling industry, this activity does not currentlyestimate the local properties of production. The potential of the tracheid effect, which enables localfiber orientation measurement, has been widely documented for sawn products. A measuring instrumentexploiting this technology and implemented on a peeling line was developed, enabling usto obtain the fiber orientation locally which, together with global density, allowed us to model thelocal elastic properties of each veneer. A sorting method using this data was developed and is presentedhere. It was applied to 286 veneers from several logs of French Douglas fir, and was comparedto a widely used sorting method based on veneer appearance defects. The effectiveness ofboth grading approaches was quantified according to mechanical criteria. This study shows that thesorting method used (based on local fiber orientation and average density) allows for better theoricalquality discrimination according to the mechanical potential. This article is the first in a series,with the overall aim of enhancing the use of heterogeneous wood veneers in the manufacturing ofmaximized‐performance LVL by veneer grading and optimized positioning as well as material mechanicalproperty modelization.Abstract: This paper presents a new strategy in the use of wood of heterogeneous quality forcomposing LVL products. The idea is to consider veneers representative of the resource variabilityand retain local stiffness information to control panel manufacturing fully. The placement of veneersis also no longer random as in the first part of this group of papers but optimized for the quality ofveneers according to the requirement of bending stresses along the beam. In a four-point bending testarrangement, this means the high-quality veneer is concentrated in the center of the beam in the areabetween the loading points where the bending moments are the most important, and the low qualityis located at the extremities. This initiates the creation of variable stiffness beams. This is driven by analgorithm developed and tested on representative veneer samples from the resource. Four LVL panelswere manufactured by positioning the veneers in the same positions as in an analytical calculationmodel, which allowed the calculation of beam mechanical properties in four-point bending. Theproposed optimization of LVL manufacturing from variable quality veneers should help for moreefficient usage of forest resources. This optimization strategy showed notable gains for modeledand experimental mechanical properties, whether in terms of stiffness or strength. The analyticalcalculation of the local modulus of elasticity from modelized beams was satisfactory compared to thetests of the manufactured beams test results, allowing the reliability of the model for this property tobe confirmed.
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Submitted on : Tuesday, May 31, 2022 - 5:20:26 PM
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  • HAL Id : tel-03683607, version 1

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Robin Duriot. Développement de produits LVL de douglas aux propriétés mécaniques optimisées par l’exploitation de la mesure en ligne de l’orientation des fibres lors du déroulage. Mécanique des fluides [physics.class-ph]. HESAM Université, 2021. Français. ⟨NNT : 2021HESAE060⟩. ⟨tel-03683607⟩

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