Influence of the number of plies on the Stiffness of Laminated Veneer Lumber
Topic(s) : Material science
Co-authors :
Axel PEIGNON (FRANCE), Joël SERRA (FRANCE), Arthur CANTAREL , Florent EYMA (FRANCE), Bruno CASTANIÉ (FRANCE)Abstract :
Wood's use in transportation isn't new, but it offers a promising solution to current environmental challenges due to its low cost, minimal carbon footprint, and light weight. Laminated Veneer Lumber (LVL) and plywood are wood composites, constructed from thin wood plies bonded with an adhesive, boast mechanical properties on par with or surpassing solid wood. Recent studies also highlight LVL's potential in crash and impact scenarios [1]. However, these wood composites, and on a finer scale, these wood plies, are heterogeneous, which leads to dispersion and a certain variability in mechanical properties. It is therefore essential to analyze them in detail to consider their use as a structural material in transport.
Research indicates that the number of plies, in an unchanging LVL’s thickness, affects its stiffness and strength [2]. This phenomenon is observed in shear, compression, tensile and bending tests: the breaking strength and rigidity is greater for LVL made with thinner plies. However, only one study has, in some extent, investigated the effect of the number of plies, of fixed thickness, on the properties of an LVL [3]. In the case of Carbon Fiber Reinforced Polymer, the laminate theory model does not predict an increase in composite stiffness as the number of plies increases, a point experimentally validated by some authors [4].
The present study aims to continue the work carried out by ICA members since 2014. LVL made up of different poplar plies are being characterized through a series of uniaxial tensile tests. The aim of this campaign is to understand and identify the mechanical properties of poplar LVL and its behavior according to the number of plies composing it.
Tensile tests on 1-, 2-, 3-, 5-, 7- and 9-ply Koster poplar (Populus) LVL were carried out to characterize the transverse and longitudinal stiffness of these laminates and the influence of the number of plies. Each ply used for the manufacturing of the tensile specimens was 1 mm thick. The tensile specimens had nominal dimensions of 250×25×thickness of LVL mm3 (according to ASTM D3039). The results show that stiffness tends to increase when the number of plies in the laminate is increasing. This observation is valid, not only for longitudinal stiffness but also for transverse stiffness, where the effect of the number of plies is even greater.
The study of the stiffness of LVL according to the number of plies composing it provides a better understanding of the link between manufacturing and the mechanical properties of the material. With a view to setting up a digital wood-based composite model, this information seems relevant.
Research indicates that the number of plies, in an unchanging LVL’s thickness, affects its stiffness and strength [2]. This phenomenon is observed in shear, compression, tensile and bending tests: the breaking strength and rigidity is greater for LVL made with thinner plies. However, only one study has, in some extent, investigated the effect of the number of plies, of fixed thickness, on the properties of an LVL [3]. In the case of Carbon Fiber Reinforced Polymer, the laminate theory model does not predict an increase in composite stiffness as the number of plies increases, a point experimentally validated by some authors [4].
The present study aims to continue the work carried out by ICA members since 2014. LVL made up of different poplar plies are being characterized through a series of uniaxial tensile tests. The aim of this campaign is to understand and identify the mechanical properties of poplar LVL and its behavior according to the number of plies composing it.
Tensile tests on 1-, 2-, 3-, 5-, 7- and 9-ply Koster poplar (Populus) LVL were carried out to characterize the transverse and longitudinal stiffness of these laminates and the influence of the number of plies. Each ply used for the manufacturing of the tensile specimens was 1 mm thick. The tensile specimens had nominal dimensions of 250×25×thickness of LVL mm3 (according to ASTM D3039). The results show that stiffness tends to increase when the number of plies in the laminate is increasing. This observation is valid, not only for longitudinal stiffness but also for transverse stiffness, where the effect of the number of plies is even greater.
The study of the stiffness of LVL according to the number of plies composing it provides a better understanding of the link between manufacturing and the mechanical properties of the material. With a view to setting up a digital wood-based composite model, this information seems relevant.