Impact of Aspen and Black Alder Substitution in Birch Plywood

: Increasing demand pressures on the fibre supply are forcing manufacturers to explore using new species in plywood. Here we investigated aspen and black alder, alone and in combination with birch faces, and with different veneer thicknesses in plywood production. The aim of this study was to evaluate the effect of different veneer thicknesses, lay-up systems, and hardwood veneer combinations on plywood mechanical properties. Impacts on modulus of rupture (MOR), modulus of elasticity (MOE), glue consumption, and density properties were observed. All process parameters were the same as for pure birch plywood. Not surprisingly, birch plywood had the highest MOR and MOE, followed by aspen and black alder. Aspen had the highest glue consumption and birch the lowest, when applied with a spreader roll, but the common practice of using relatively thick 2.6 mm aspen veneers resulted in the lowest glue consumption per mm of product. The effects of wood species and veneer thickness on MOR, density, and glue consumption were analysed for panel thicknesses from 6.5 to 18 mm to guide manufacturers in choosing their species and construction to optimize cost, MOR and stiffness, weight, and glue consumption. In conclusion, birch gave the best strength properties while aspen gave the best price and weight combination.