The grading of wood veneers according to their true mechanical potential is an important issue in the peeling industry. Unlike in the sawmilling industry, this activity does not currently estimate the local properties of production. The potential of the tracheid effect, which enables local fiber orientation measurement, has been widely documented for sawn products. A measuring instrument exploiting this technology and implemented on a peeling line was developed, enabling us to obtain the fiber orientation locally which, together with global density, allowed us to model the local elastic properties of each veneer. A sorting method using this data was developed and is presented here. It was applied to 286 veneers from several logs of French Douglas fir, and was compared to a widely used sorting method based on veneer appearance defects. The effectiveness of both grading approaches was quantified according to mechanical criteria. This study shows that the sorting method used (based on local fiber orientation and average density) allows for better theorical quality 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 of maximized-performance LVL by veneer grading and optimized positioning as well as material mechanical property modelization.

This paper presents the experimental results of the bending mechanical behavior (static and dynamic moduli, and maximum stress) of LVL (Laminated Veneer Lumber) beams reinforced with fiber polymer material (FRP). Different variables were studied: i) Wood species (Douglas fir or poplar); ii) Type of reinforcement (bidirectional carbon, unidirectional carbon or basalt); iii) Veneer quality and iv) Veneers orientation in the beam (flatwise or edgewise). The reinforcement percentages respect to the total cross-section was of 2.17%, 0.89% and 1.74% for the unidirectional carbon, bidirectional carbon and basalt, respectively. A clear improvement provided by unidirectional carbon has been demonstrated (up to 40% more in the elastic modulus for the flatwise layout and more than 20% of the maximum stress, for both wood species). The influence of the quality of the veneers of the panel was also clearly demonstrated: the weakest wood material obtained the greatest improvements in their mechanical properties when reinforced, allowing to obtain stiff second quality poplar LVL, or strong second quality Douglas fir LVL.

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This paper presents a new strategy in the use of wood of heterogeneous quality for composing LVL products. The idea is to consider veneers representative of the resource variability and retain local stiffness information to control panel manufacturing fully. The placement of veneers is also no longer random as in the first part of this group of papers but optimized for the quality of veneers according to the requirement of bending stresses along the beam. In a four-point bending test arrangement, this means the high-quality veneer is concentrated in the center of the beam in the area between the loading points where the bending moments are the most important, and the low quality is located at the extremities. This initiates the creation of variable stiffness beams. This is driven by an algorithm developed and tested on representative veneer samples from the resource. Four LVL panels were manufactured by positioning the veneers in the same positions as in an analytical calculation model, which allowed the calculation of beam mechanical properties in four-point bending. The proposed optimization of LVL manufacturing from variable quality veneers should help for more efficient usage of forest resources. This optimization strategy showed notable gains for modeled and experimental mechanical properties, whether in terms of stiffness or strength. The analytical calculation of the local modulus of elasticity from modelized beams was satisfactory compared to the tests of the manufactured beams test results, allowing the reliability of the model for this property to be confirmed.