A numerical study on the influence of the bond-line diffusivity on moisture-related stresses and deformations of three-layered spruce cross-laminates

摘要

The glue lines play an important role in diffusion processes through glued wooden elements. For the numerical calculation of the moisture distribution, the diffusion coefficient of the adhesive is needed. In previous studies it was evaluated from moisture measurements and found to be significantly lower than that of wood. The aim of this article is to apply this knowledge. Numerical studies on the influence of different diffusivities on warping and stresses in three-layered spruce cross-laminates were performed. The objective was to reduce moisture-induced stresses and deformations of cross-laminates to improve their performance. The results revealed a significant influence of the bond-line diffusivity on moisture content. The influence on warping, which was induced by a moisture gradient, is also very significant. A 25% reduction of deformation was achieved by applying diffusivity identical to that of the wood. Significant differences in stresses occurring perpendicular to the grain were detected only in the middle layer. Stresses in the outer layers were not affected by changing the diffusivity of the glue. In conclusion, an adhesive with high moisture permeability should be applied to reduce the results of moisture impact on cross-laminated timber.