Nonlinear viscoelastic response of a wood-plastic composite including temperature effects

Current timber waterfront structures require the use of treated lumber to reduce environmental damage. Wood-plastic composites (WPCs) have been proposed as an alternative to treated timber due to their potential for reduced water absorption and degradation without chemical treatment. Even though WPCs are primarily made of wood (58% wood flour in the current case) their mechanical response to applied loads is quite different. The current study attempts to describe the time and temperature dependence of a commercial WPC formulation. Characterization of the formulation was undertaken by means of a series of creep and recovery tests. A Prony Series was used to describe the material's time dependent compliance, where time was shifted with stress and temperature to describe the observed nonlinear response and temperature dependence. Damage effects were successfully correlated isothermally using an effective stress. The model was evaluated by comparing the behavior predicted by the model with experimental results in 3-point bending and fatigue.