Viscoelasticity behavior of modern and aged wood

In order to compare the mechanical behavior of the modern and old spruce wood (Picéa Abies), a microtensile test machine has been used. The size of the samples were 3x3x30 mm. Elastic, creep, relaxation and rupture tests under controlled temperature and relative humidity were carried out on the radial directions. Moreover, some micrographs have been done, in order to correlate the mechanical behavior with the structure. Preliminary results indicate that in general the global mechanical parameters, such as Young’s modulus and time dependent behavior of natural aged wood does not modify extremely. However, the rupture-stress of old wood shows a decrease of about 25%. These losses of strength in the old wood might be explained by the localized damages in the micro level of wood.