Wood-based sandwich panels are building products composed of two skins attached to a lightweight continuous core in which at least one skin is made of wood-based products, contributing to the use of renewable forest goods. Since the connection between the skins and the core is often provided by adhesive bonding, its characteristics affect the mechanical behavior of the sandwich and, therefore, must be thoroughly assessed. Full adhesion is often considered the standard situation, although some batches of the commercial product show incompletely glued surfaces, and scarce data is available with regard to their bonding performance. For this reason, analyses were performed using tensile tests with a load perpendicular to the skins and specific shear tests with a load parallel to the longitudinal direction of the panel. The test samples were obtained from wood-based sandwich panels with extruded polystyrene cores and different skin materials. The tensile tests proved to be suitable only for panels with adequate skin material cohesion, their functionality improving as a control method when the glued surface percentage assessment is used together with the tensile strength. The results of the shear tests provided non-linear models relating the effect of the glued surface to the mechanical properties, revealing that the mechanical efficiency of the incompletely bonded specimens is better than that which might be expected if the core only worked in proportion to the glued surface, due to the help of the adjoining non-glued core material.

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