The effect of (induced) dislocations on the tensile properties of individual Norway spruce fibres

Abstract

Abstract Axial compressive stresses can cause distortion of the cellulose fibril alignment in the wood cell wall. These deformations are thought to occur in the living tree and/or to develop during wood processing and seem to adversely affect the mechanical properties of pulp and paper and other fibre-based products. To characterise the influence of dislocations on the mechanical properties of the unmodified cell wall, dislocations were artificially created by applying high compression loads to wood blocks parallel to the fibre axis. Mechanically isolated fibres containing different levels of dislocations were then subjected to tensile tests. Comparison between micromechanical properties of reference fibres and fibres that were artificially loaded in compression revealed the importance of dislocations for the mechanics of both earlywood and latewood. However, the tensile strength (decrease ∼19% for earlywood and ∼26% for latewood) was less affected than expected from structural observations of the pre-compressed zones.