Oak timber cross-cutting based on fiber orientation scanning and mechanical modelling to ensure finger-joints strength

Abstract

The mechanical properties of wood depend on its characteristics at different scales, in particular its knots and the orientation of its fibers. As wood is a highly anisotropic material, its strength and elastic properties are much better in the longitudinal direction of the fibers than in the perpendicular directions, so the orientation of the fibers is an extremely important parameter. Finger-jointing is a technique for joining sawn timbers into large panels for structural use, such as finger-jointed panels (GLT) and laminated timbers (CLT). In this study, the tensile strength of oak sawn timbers was modelled by considering the local fiber orientation obtained by using laser diffusion patterns onto the timber faces. Strength thresholds were established to ensure an equivalent mechanical performance to T11 tensile strength class, with the possibility of cross-sectional splitting if required. In addition, the tensile strength of the finger-joints was determined in accordance with (NF EN 14080 2013). Lamellas were assembled, glued and subjected to tensile tests, and the method was found to be satisfactory in terms of characteristic strength of the finger joints.