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

To understand and predict hygrobuckling behavior of orthotropic or isotropic wood-based composite panels, the closed form equations were derived using both the displacement function with a double sine series and the energy method under biaxial compressions with an all-clamped-edge condition. The critical moisture content depended on Poisson's ratio () and was inversely proportional to 1+ for isotropic panels. It did not depend on the modulus of elasticity (MOE) at all for isotropic panels, but it did depend on MOE ratios for orthotropic panels. As expected, the critical moisture content of plywood was twice as large as the that of hardboard owing to the difference in linear expansions between the two panels. The application of optimum thickness and aspect ratios obtained by the derived equations could improve hygrobuckling resistance without other chemical treatments that could reduce 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 (a/h) from the view-point economics.