Potential of adhesive bonding technology for joining thermo-mechanically modified wood composites in automotive application

Wood composites are a sustainable alternative to lightweight materials, but most often only possess low to medium mechanical properties. The stiffness and strength of wood-based panels can however greatly be enhanced by a densification process. In this context the question arises as to whether the increase in density and the associated compaction of the cell structure have a lasting effect on the adhesion of binders and the overall bonding ability. This paper therefore investigates the extent to which thermo-hydro-mechanical compression at different pressure levels affects the adhesive infiltration into laminated beech veneer composites. For this purpose, not only the mechanical properties of the plywood are analysed, but also the infiltration of polyurethane and polyvinyl acetate adhesives by fluorescence microscopy. Results show that although the infiltration capacity of the adhesives is impaired by the densification, higher degrees of compression are also accompanied by superior mechanical properties.