Postbuckling of thin wood-based sandwich panels due to hygroexpansion under high humidity

This study was carried out to investigate the postbuckling behavior of thin wood-based sandwich panels under high humidity. Using the Rayleigh-Ritz method based on the von Karman nonlinear theory for the panel, the solutions for both the approximate and the closed form for postbuckling of orthotropic panels were derived to evaluate the deflection for the boundary condition of all clamped edges. The results suggested that the edge movement be considered for evaluation of a critical moisture content and deflection of thin wood-based panels fixed on the core with an adhesive. The numerical solution obtained from the derived model showed some discrepancy with the experimental results. The predicted results overestimated the center deflection of the panels because creep and plastic deformation might be caused by considerable in-plane stress on panels.Appendix: Abbreviations and symbols total potential energy of panel - A_ij,D_ij extensional and bending stiffness, respectively - _x,_y midplane strains inx andy directions, respectively - _xy midplane shear strain inxy plane - N_x^M, N_y^M hygroscopic forces inx andy directions, respectively - h panel thickness - a, b panel length inx andy directions, respectively - x, y, z coordinate system - u, v, w displacement inx, y, andz directions, respectively - MC moisture content change - a_x,a_y coefficient of linear expansion inx andy directions, respectively - LE linear expansion (MC) - s arc length - R radius of curvature - N_x,N_y resultant in-plane forces per unit length inx andy directions, respectively - N_n nondimensional loadN_x^Mb²/E₂h³ - N_cr nondimensional critical load,N_x,cr^Mb²/E₂h³ - ratio of the core to the total width,a_c/a + a_c - E_c effective core MOE,E+E (i.e., the summation of MOE parallel to the grain and perpendicular to the grain) - h_c core thickness