Prediction of stiffness and strength distributions in laminated-wood treated by high voltage electrostatic field (HVEF)

Abstract High voltage electrostatic field (HVEF) treatment was an effective approach to improve mechanical properties of wood composites. In this study, laminated poplar (Populus tomentosa) and masson pine (Pinus massoniana Lamp.) in different plies were hot-pressed and treated by HVEF simultaneously. Mechanical properties at macroscopic and microscopic (cell wall) scales of laminated-woods were determined, and vertical density profile (VDP) and adhesive distribution along thickness direction were explored as well. Representative volume element (RVE) with a thickness of 50 μm was proposed to model stiffness and strength distributions in laminated-wood. The predicted stiffness of RVE was well correlated with the value tested by nanoindentation. Based on the calculated elastic constants and strength of RVE, macro-mechanical properties [modulus of elasticity (MOE), modulus of rupture (MOR), shear modulus (G), shear strength (SS)] of treated laminated-woods were predicted. Great agreements were observed between theoretical and experimental values for all these macro-mechanical properties. It was proved that RVE model was able to predict the distributions of stiffness and strength of HVEF-treated laminated-wood. The results of this study revealed that: the concentration of adhesive along bondline was the main reason for increasing stiffness, strength of laminated-wood, which would be helpful to optimize manufacturing technique of HVEF treatment.