Production of laminated boards with different glues and mechanical characterization with digital image analysis method

The aim of this paper was provide a more efficient of bonding by foaming polyvinyl acetate (PVA) and thus by increasing the interactions between wood layers, the plywood panels with enhanced mechanical properties is to obtain. The effects of cellulose nanofibrils (CNFs) on the bonding strength and morphological properties of the PVA, and glass fiber (CF) fabrics on the bonding quality of wood layers also were examined. In the foaming process, egg white (EW) were used as foaming agents, and the foaming was provided by blending PVA and EW using a mixer at 1000 rpm. Both un-foamed and foamed PVA was then applied onto the surface of the wood veneers via a brush at room temperatures, and a woven CF fabric was added to between wood veneer layers. The morphological, thermal, structural properties of CNF and the foamed/unfoamed PVA with CNF, and the bonding strength, flexural strength, flexural modulus and strain analysis occurred under tensile stress in the plywood panels produced were examined. The obtained results showed that Cellulose nanofibrils were characterization with SEM, AFM, XRD and TG-DTA, and the diameters of CNF were determined to change from 25 nm to 35 nm. The CNF exhibited crystalline peaks at 15.9°, 22.6° and 34.5°. Characterization of un-foamed and foamed PVA with CNF were characterized with similar methods. The morphological structure and cell size were determined with SEM. XRD pattern were detected at ranges from11.9° to 23.5°. TG-DTA showed that the adding CNF and foaming process haven't an improvement effect on the thermal stability. The foaming process and the adding CNF improved the bonding strength, however, both flexural strength and modulus generally decreased with the adding CNF and foaming process, and the GF didn't have provide any improvement on the flexural strength and modulus. Digital image correlation (DIC) analysis revealed to be more strain distribution in the samples with foamed/unfoamed PVA with CNF under loading