Viscoelastic Properties of Wood-Fiber Reinforced Polyethylene: Stress Relaxation, Creep and Threaded Joints

By: Syed Imran Farid

Master of Applied Science - 2000
©University of Toronto and Syed Imran Farid

Department of Mechanical and Industrial Engineering, University of Toronto

ABSTRACT
Tensile stress relaxation and flexural creep experiments were performed to evaluate the viscoelastic properties of WFRP. The effect of time, temperature and loading conditions were investigated. In stress relaxation experiments, the modulus relaxed rapidly within a short period of time and then a slow relaxation was observed. In creep experiments, at lower stress and temperature, the strain increased rapidly within the short period of time and then slow creep was observed. At higher stress and temperature, the specimen ruptured after a rapid increase in strain to a maximum of 3% strain. WFRP performed better than low-density polyethylene but the long-term effects did not match those of wood. The Power Law was found to be appropriate to describe the viscoelastic behavior of the material but at the same time it suggests that the modulus relaxes infinitely.

Wood screw and Plastite screw were found to be better than post molded inserts. The pullout force was also found linearly dependent on the engagement length. The pullout force for WFRP was found comparable with spruce. The clamping force relaxed rapidly within the short period of time and then a slow relaxation was observed