Bond integrity of cross laminated timber from Acacia mangium wood as affected by adhesive types, pressing pressures and loading direction

Abstract

Cross laminated timber (CLT) was fabricated from Acacia mangium wood by using phenol resorcinol formaldehyde (PRF) and one component polyurethane (PUR) as binders. The purpose of the study was to evaluate the bond integrity of A. mangium CLT produced using different working parameters. The assemblies were pressed at 30 °C for 30 min using three pressing pressures (0.9 N/mm2, 1.2 N/mm2, and 1.5 N/mm2). Delamination and block shear tests were conducted on the CLT according to European Standards, EN 391 and EN 392, respectively. The results revealed that PRF-bonded CLT experienced lower percent delamination compared to that bonded with one component PUR. It appears that a higher clamping pressure i.e. 1.5 N/mm2, is needed to sufficiently bond A. mangium lumbers as indicated by a marked increase in bond shear strength with an increase of pressing pressure. PRF was found to be a more superior adhesive than PUR irrespective of cramping pressure and loading direction. A. mangium wood is relatively dense thus requires quite high pressure, 1.5 N/mm2, irrespective of adhesive used. PRF appears to bond A. mangium wood better compared to PUR with shear bond strength of 21% and wood failure percentage of 220% higher.