Analysis and testing of corrugated board panels into the post-buckling regime

Testing of the load bearing capacity of corrugated board boxes is often associated with uncertainties, e.g. the creases along the edges of the side panels introduce eccentricities. An alternative to the testing of boxes is therefore attractive. One suggestion is testing of panels. However, panels are sensitive to the boundary conditions. A panel compression test (PCT-) rig, similar to a test frame for metal plates designed by A.C. Walker, was therefore built to achieve accurately defined load and boundary conditions. The PCT-rig furnishes simply supported boundary conditions, i.e. the edges of the panel are prevented from moving out-of-plane without any rotational restraint. The edges are also free to move in-plane. In order to describe the buckling behaviour, a non-linear buckling analysis of orthotropic plates, derived by Rhodes and Harvey, was modified to include initial imperfections. The critical buckling load of the panels was evaluated by fitting the analytical expression by non-linear regression to experimentally measured load–displacement curves. The results show a difference in the order of 15–20% between experimentally estimated critical buckling load and the analytically predicted critical buckling load for orthotropic plates. This is mainly attributed to transverse shear deformations. A corresponding difference was observed between analytically predicted and experimentally measured load–displacement curves at large out-of-plane deformation, i.e. twice or three times the board thickness. This is probably caused by the non-linear response of paper at high stresses and local buckling of the panel facings, i.e. the liners. A predicted failure load of the corrugated board panel was determined when stresses in the facings reached the Tsai–Wu failure criterion. The predicted failure load and measured average experimental failure load were close, indicating that collapse of the panel is triggered by material failure of one of the liners.