Summary

The transverse mechanical properties of the wood fibre play important roles in the use of wood and its fibres in various applications. However, the variation in properties of fibres from different parts of the tree and the relation of these properties to the structure of the fibre is not yet established. This study focuses on the variation in the transverse elastic modulus of the fibre wall and its relation to the fibril structure of the S₂- and S₁-layer. For this reason the local fibril angle of radial and tangential fibre walls were measured by polarisation confocal microscopy. It was shown that the variation in fibril angle of the S₂-layer seems to have very little influence on the transverse modulus of the fibres. Instead the thickness and fibril angle of the S₁- and thus also the S₃-layer should contribute to the variation in transverse modulus between earlywood and transition wood fibres. The importance of the ray cells for the transverse elastic properties of the wood was also emphasised.