INFLUENCE OF STRAIN-RATE AND TEMPERATURE ON THE RADIAL COMPRESSION BEHAVIOR OF WET SPRUCE

In the mechanical pulping process, wood is treated in compression and in shear at high temperatures in the wet state, To separate the fibers and also to increase the bonding ability and flexibility of the fiber s in order to obtain strong paper sheets. This is probably enhanced by permanent deformation and collapse of the fibers. In this study: the influences of moisture content, density: strain I are and temperature on the mechanical response of spruce compressed radially to 50 percent strain were investigated. Regression models were obtained for the pla teau stress (approximate to collapse stress), energy absorption, plast ic strain and reduction of plateau stress after the first compression. Temperature and strain rate had a great influence on the mechanical b ehavior of spruce. It was found that lumen (= cell void) water had a s ignificant effect on the deformation process at high strain rates. The reduction in plateau stress after one compression was about 30-55 per cent, which might increase the collapsibility of the wood fibers.