Shear Creep of Polystyrene Cores in Wood-Based Panels

This paper reports on an experimental study of shear creep in load bearing sandwich panels with a polystyrene core and wood-based faces. This is ongoing research at Eindhoven University of Technology (TU/e), in cooperation with industry, to provide scientific and experimental backgrounds to roof panels used for residential housing. For these panels, loaded perpendicular to plane, faces are loaded in tension or compression, whereas the core is mainly loaded in shear. Both the polystyrene core and the wood-based faces show time dependent behaviour (creep) of which only the time dependent behaviour of the core is dealt with in this paper. This by including experiments on panels of which the wood-based faces are replaced by steel, thus isolating the creep of the core. Furthermore, conform other studies on this subject, e.g. Taylor et al. [1], and Kilpeläinen et al. [2], the study presented in this paper indicates that the creep depends on the load ratio, i.e. the quasi-permanent shear relative to the shear stress at failure (strength). Therefore, load ratios were systematically varied. Results indicate that when the shear stress exceeds more than 50% of the shear strength, the tertiary creep phase is reached, and collapse will occur within 4 -5 years. When the shear stress is lower than 40% of the shear strength, the deformation is likely to stabilise in the secondary creep phase.