Some elasto-mechanical properties of black locust laminated veneer lumber under dry and wet conditions

Black locust (Robinia pseudoacacia L.) has great potential for weathered exterior applications due to its natural durability and density. In particular, the narrow sapwood range and the crooked trunk areas with strong fiber inclination make the production of veneer lumber from shorter logs very interesting, except for logs with a tension back. This paper describes selected elasto-mechanical properties of robinia laminated veneer lumber, tested in a climate of 20 °C and 60% relative humidity and at the fiber saturation point. In particular the Young’s modulus (E_L, E_R, E_T) in tension, the Poisson’s ratios (µ_LT, µ_TR, µ_LR), and the strengths (σ_L, σ_R, σ_T). were determined experimentally by tensile tests, and the lateral strain coefficients µ_TL, µ_RT, and µ_RL were calculated from these values. The results show a significant decrease in Young’s modulus and modulus of rupture with increasing wood moisture content in the longitudinal, radial, and tangential directions. There was no notable dependence of the lateral strain coefficients on moisture content. Additionally, no significant correlations were observed between the investigated properties and gross density, nor between Young’s modulus and tensile strength. Unlike Young’s modulus and tensile strength, the lateral strain coefficients showed no clear trend with increasing wood moisture content. The strain coefficients are in good agreement with literature values, but further research with larger samples and different material sources is needed to complete the engineering constants. In addition, characteristic values of component size and material durability are of interest for future development.