A. Reiterer et al., Deformation and energy absorption of wood cell walls with different nanostructure under tensile loading, J MATER SCI, 36(19), 2001, pp. 4681-4686
The nanostructure of the S2 cell wall layer in tracheids of Picea abies (No
rwegian spruce), in particular the cellulose microfibril angle, has been sh
own to control not only the stiffness but also the extensibility of wood wi
thin a wide range. In order to further elucidate this effect, the deformati
on of wood under tensile load parallel to the longitudinal cell axis was st
udied in a contact-free way using a video extensometer. The combination of
these measurements with small-angle X-ray scattering on the same microtome
sections allowed us to establish a direct relationship between the microfib
ril angle and deformation behaviour. The microfibril angle was shown to inf
luence not only the extensibility in longitudinal direction but also the de
formation perpendicular to the applied load. Moreover, the results showed t
hat the energy absorption capacity is higher for specimens with larger micr
ofibril angle. SEM pictures of the fractured samples indicated clearly the
differences in the fracture process as the fracture zones of samples with l
ow microfibril angle were smooth and the fracture zones of samples with hig
h microfibril angle were heavily torn and deformed indicating a more ductil
e behaviour. (C) 2001 Kluwer Academic Publishers.