Adhesively Bonded Hardwood Joints under Room Temperature and Elevated Temperatures

Timber engineering sets high expectations on adhesive bonding as a joining method to overcome a series of limitations related to partly obsolete traditional techniques. Research on adhesively bonded timber joints has proved their superiority over mechanical fasteners in terms of strength and stiffness, but this research was often limited to softwood. Despite its abundant availability in Central Europe and its high mechanical resistance, beech is only rarely considered as a structural material. Furthermore, research on adhesively bonded timber joints almost exclusively focused on tests at room temperature. Elevated temperatures, however, are critical in conjunction with adhesives, making it paramount to shed more light on that particular aspect. Based on experimental and numerical investigations, it was found that the capacity of adhesively bonded hardwood joints increased asymptotically with overlap length to a ceiling value; furthermore, it was concluded that temperature negatively impacts capacity. Glass transition temperature, T g, marked a clear transition, but joints still sustained relatively high loads beyond T g. A probabilistic approach was validated and successfully applied to predict the joint capacity. The research contributes to fill knowledge gaps by offering the basis for subsequent dimensioning methods that at term will enable practitioners to design their structures accordingly.