Creep response of wood flour-high-density polyethylene/laminated veneer lumber coextruded composites

Coextruded composites (CEC) with a core-shell structure were manufactured, with laminated veneer lumber (LVL) as the core layer and wood-plastic composites (WPC) as the shell layer. The creep responses of the LVL and CEC at stress levels of 30%, 40%, and 50% of ultimate flexural strength at room temperature were determined using the three-point bending test. The creep parameters of the CEC and LVL were determined by in-house creep testing. The first derivative of creep strain results indicated that the creep performance of the CEC was more stable than that of the separate LVL in an unstable external environment. Three different widely known creep models in the literature, including the Burger model, Findley power law model, and Bailey-Norton model, were used to model the creep behavior of LVL and CEC in this study. The correlation coefficients of all nonlinear fitting curves exceeded 0.9, while the predicted values of the Burger model and Bailey-Norton model were deviated from the experimental values in the later stage of experiment. The creep formula for the LVL and CEC obtained based on the Findley model can be used to predict their long-term creep behavior. These findings have increased the selection range of environmentally friendly load-bearing materials that can be adapted to hot and humid environments, as well as the application of WPC and LVL. (C) 2019 Elsevier Ltd. All rights reserved.