Effects of material constants and geometry on hygrobuckling of wood-based panels

To understand and predict hygrobuckling behavior of orthotropic or isotropi c wood-based composite panels, the closed form equations were derived using both the displacement function with a double sine series and the energy me thod under biaxial compressions with an all-clamped-edge condition. The cri tical moisture content depended on Poisson's ratio (v) and was inversely pr oportional to 1 + v for isotropic panels. It did not depend on the modulus of elasticity (MOE) at all for isotropic panels, but it did depend on MOE r atios for orthotropic panels. As expected, the critical moisture content of plywood was twice as large as the that of hardboard owing to the differenc e in linear expansions between the two panels. The application of optimum t hickness and aspect ratios obtained by the derived equations could improve hygrobuckling resistance without other chemical treatments that could reduc e the linear expansion of wood-based panels. This study also indicated that it would be better to increase the aspect ratio rather than the thickness ratio (alh) from the viewpoint economics.