Mode I fracture energy release rates of European beech wood-adhesive bonds

This paper presents mode-I fracture energy release rates (GI) of European beech wood (Fagus sylvatica) adhesive bonds for three common types of adhesives pressed with two levels of pressure and glued with three spread rates. Flat double cantilever beam tests with a shear corrected compliance method were used to derive GI. A high pressing pressure of 1.0 versus 0.1 MPa resulted in higher GI-values for phenol resorcinol formaldehyde and melamine urea formaldehyde adhesive systems (not significant), but did not affect the polyvinyl acetate system. A low adhesive spread rate of 50 g m−2 clearly resulted in lower GI-values for all three systems, while no clear differences were found between spread rates of 100–200 g m−2 for the formaldehyde systems. The herein presented GI-values of beech adhesive bonds can be used to further evaluate the suitability of beech in glued load-bearing timber structures and promote optimising beech wood-adhesive systems for high GI.