Longitudinal shrinkage in gelatinous layer : from observations to modelling

Tension woods containing a gelatinous layer, mainly composed of cellulose with very low or nil microfibril angle exhibits a high longitudinal shrinkage. These observations contradict the usual relation between microfibril angle and longitudinal shrinkage. Observations under Scanning Electronic Microscope and Atomic Force Microscopy show the presence of a high longitudinal shrinkage in G-layer. An estimate of 4.7% longitudinal shrinkage for G layer was obtained from observation on 80 [mu]m thick sections. A finite element modelling of the cell wall, simplified as an axisymmetrical superposition of concentric layers, was developed to analyse the results. The simulation includes the study of the progressive delamination resulting from the differential shrinkage of the cell wall layers. (Résumé d'auteur