The potential of wood ray cells in beech (Fagus sylvatica) as a design parameter for veneer-based products

A potential reinforcing effect of wood rays in sliced beech was investigated to enhance predictability and performance of engineered wood products. By a microscopic characterisation, the in- and out-of-plane fibre angle, and the wood ray angle (WRA), were determined on various decks of veneers. Young’s modulus (E) and modulus of elasticity (MOE) were measured in tensile and 3-point bending tests, respectively. Besides the density, lathe checks from the slicing process appeared to affect the flexural properties. To minimise this distortion, the bending specimens had to be positioned with the lathe checks on the upper/compression side. Plotting the MOE over the WRA revealed that the MOE at 90° WRA (i.e. rays oriented perpendicular to the veneer surface) yielded only approximately 50 % of the values obtained at a WRA of 0° (i.e. rays were oriented parallel to the veneer surface). Alike for bending, E and tensile strength featured a decline in mechanical properties of roughly two third between a WRA of 0–20°. Furthermore, it was shown that analytical models predicting stiffness and strength of solid and plywood as a function of the fibre orientation are applicable for modelling the mechanical properties of veneers perpendicular to the grain using the WRA instead of the fibre orientation. Fitting these models to the data points resulted in a coefficient of correlation of about 0.8. These results reveal an unexploited potential to enhance the material efficiency and predictability of veneer-based wood products for structural applications by using the reinforcing effect of wood ray cells. • Improve predictability of engineered wood considering ray cells. • Wood ray cells act as reinforcement in sliced veneers. • Implementation of wood ray angle as new design parameter. • Analytical model to describe mechanical effect of wood ray orientation.