Wood bonding by vibrational and rotational friction welding

Mechanically-induced wood welding, without any adhesive yields wood joints satisfying the relevant requirements for structural applications. The mechanism of mechanically-induced vibrational wood fusion welding is due mostly to the melting and flowing of some amorphous, cells- interconnecting polymer material in the structure of wood, mainly lignin, but also hemicelluloses. This causes partial detachment, the "ungluing" of long wood cells, wood fibres, and the formation of a fibres entanglement network in the matrix of molten material which then solidifies. Thus, a wood cells/fibres entanglement network composite having a molten lignin polymer matrix is formed. Cross- linking chemical reactions also occur. These reactions have been identified but are relatively minor contributors during the very short welding period. Their contribution increases after welding has finished, explaining why long holding times under pressure after the end of welding contribute strongly to obtaining a good bond.