The influence of false heartwood of European beech (Fagus sylvatica L.) on tensile shear strength of lap joints

The aim of this research was to investigate the effect of false heartwood of beech wood on the shear strength of glued joints for thermoplastic and reactoplastic adhesives for plywood production. The tensile shear strength of the lap joints was tested for four different types of adhesives according to EN 204 (2016) and EN 205 (2016). The results showed that for lap joints assembled with polyvinyl acetate, urea-formaldehyde, and phenol-formaldehyde adhesives, there was no significant difference in shear strength between beech sapwood and false heartwood. However, for joints bonded with polyurethane adhesive, the shear strength was lower for heartwood compared to the reference sapwood, particularly after exposure to water immersion.