Effect of lamination on the dynamic shear modulus of solid and laminated Fagus crenata Blume wood by torsional vibration testing

Abstract

This study evaluates the effect of lamination on the density and dynamic shear modulus (G) in torsion of Fagus crenata Blume wood using torsional vibration testing on small specimens. Two material conditions were analyzed: solid wood and laminated wood, the latter manufactured from thin layers oriented parallel to the longitudinal direction and bonded with melamine–urea–formaldehyde adhesive. Density was determined according to ISO 13061-2, and the shear modulus was estimated from the natural frequency of vibration using the impulse excitation method. The results showed an increase in density in laminated wood compared to solid wood, attributed to material densification and adhesive incorporation during manufacturing. However, no statistically significant differences were found in the shear modulus between both conditions (P > 0.05), although a slight increase and reduced variability were observed in laminated wood. The relationship between density and shear modulus was consistent with trends reported in the literature, confirming the dependence of mechanical behavior on the internal structure of wood. These findings indicate that lamination modifies the structural distribution and homogeneity of the material without necessarily producing a significant increase in stiffness, highlighting the role of adhesive interfaces in shear stress transfer. The results provide relevant experimental evidence for understanding the torsional behavior of homogeneous laminated wood configurations