Effect of PF resin penetration on interphase microstructure and quantitative micromechanical properties of different grained-wood laminates

Abstract Wood, a natural anisotropic material, behaves differently in the radial (R) and tangential direction (T), which also gives rise to different penetration capacity of adhesive into wood tissues. The present study investigates the penetration behavior of adhesive in the interphase of three different wood laminates, namely R-R, T-R, and T-T combinations, and its effect on microstructure and micromechanical properties of the latewood bonding interphase using confocal laser scanning microscopy (CLSM) and nanoindentation (NI). The results showed that the average penetration depth (AP) of the radial surface ( S R ) was higher than that of the tangential surface ( S T ) and a significant improvement in the mechanics of cells compared with the control cell ( C ). the maximum reduced elastic modulus ( E r ) and hardness ( H ) found at the fourth cell row were 21.7 GPa and 0.62 GPa for R-R laminate, respectively, which increased by 43% and 29% compared with C (15.1 GPa, 0.48 GPa), and the maximum E r and H found at the first cell row were 23.2 GPa and 0.65 GPa for T-T laminate, respectively, which increased by 52% and 44% compared with C (15.3 GPa, 0.45 GPa). The results provide an important platform for better understanding and predicting the properties of wood glue line and bonding interphase.