Effects of fiber size on short‐term creep behavior of wood fiber/HDPE composites

When natural fiber‐thermoplastic composites are used in long‐term loading applications, investigating creep behavior is essential. The creep behavior of high‐density polyethylene (HDPE)‐based composites reinforced with four sizes of wood fibers (WFs) (120–80, 80–40, 40–20, and 20–10 mesh) was investigated. The instantaneous deformation and creep strain of all WF/HDPE composites increased at a fixed loading level when the temperature was increased incrementally from 25 to 85°C. At a constant loading level, composites containing the larger‐sized WFs had better creep resistance than those containing smaller‐sized fibers at all measured temperatures. The creep properties of composites with smaller‐sized WFs were more temperature‐dependent than those with larger‐sized WFs. Two creep models (Burger's model and Findley's power law model) were used to fit the measured creep data. A time–temperature superposition principle calculation was attempted for long‐term creep prediction. The Findley model fitted the composite creep curves better than the four‐element Burger's model. From the predicted creep response of the WF/HDPE composites, two groups of small fibers (120–80 and 80–40 mesh) had the lowest creep resistance over long periods of time at the reference temperature of 25°C. The largest WFs (10–20 mesh) provided the best composite creep resistance. POLYM. ENG. SCI., 55:693–700, 2015. © 2014 Society of Plastics Engineers