DENSIFIED WOODEN NAIL FOR ADHESIVE- AND METAL-FREE TIMBER ASSEMBLES

Abstract

The widespread utilisation of adhesives to assemble engineered wood products may lead to environment and recycle concerns. To improve materials sustainability and recovery at the end-of-life, it is preferable to replace adhesive with mechanical lock-in fasteners such as wood-based connectors. Nowadays, the development of robotic fabrication technologies and wood modification technologies brings the opportunity to rejuvenate traditional wood-joining methods. In this study, thermo-hydro-mechanical densified wooden nail were proposed as an adhesive- and metal-free connector for timber assembles. The densification ratio varied between 40 to 68%. Research has been performed in order to determine the effect of densification on the compression behaviour of wood in the form of nails. The result showed that densification with high compression ratio can successfully increase the density and modulus of rupture of wood, while its influence on modulus of elasticity is not obvious. A set of prototype nails made of densified wood was manufactured. In addition, preliminary insertion tests into wood samples were carried out and served for insertion process understanding. The results obtained reveal a potential for using the densified wooden nail connectors for substitution of adhesive or metal connectors. However, the “success ratio” for proper inserting of wooden nails was not satisfactory. It was observed that the excessive dynamical loading induced buckling failure of the nail during hand-operated insertion.