Effects of Poplar Wood Fiber (PWF) Size on Mechanical Properties of PWF/Epoxy Resin Composites

Poplar wood fiber (PWF) with different sizes was prepared from poplar residues of chemi-mechanical pulping and subsequent treatments (directly drying and solvent replacement). The PWF/epoxy resin (PWF/E51) composites were prepared by hot pressing molding method. The effects of fiber size on the mechanical properties of composites were investigated by the analysis of micro-morphology and size of the PWF as well as the micro-morphology of the impact fracture surface of the composites. The results showed that the fiber size had a significant effect on the mechanical properties of composites. With the increase of the ratio of length to diameter of PWF, the impact and flexural strength of PWF/epoxy resin composites were increased first and then decreased. Among them, the PWF with the ratio of length to diameter 14.8, which were prepared from the solvent replacement, showed the best reinforcement of the mechanical strength of the epoxy resin composites. And the impact strength and flexural strength were 7.1 kJ/m² and 68.2 MPa, respectively. In addition, the mechanical strength of composites reinforced with the solvent replacement PWF was higher than that reinforced with the directly dried PWF.