Mechanical behaviors of composites made of natural fibers through environmentally friendly treatment

Natural fiber reinforced composites have garnered significant interests as potential substitutes for conventional materials because of their eco-friendly attribute and favorable physical and mechanical properties. Typically the natural fiber undergoes chemical treatment before processing with the matrix to produce composites, however, the chemical treatment can have a negative impact on the environment. This research work presents an environmentally friendly treatment method for hemp fibers by using boiling water and shear force for specific time periods. The purpose of the treatment is to break down the technical fiber bundles into elementary fibers, which creates a fourfold increase in bonding surface area between the fibers and matrix. The change in fiber length and size before and after the debundling treatment were analyzed using optical microscope, confocal microscope, and scanning electron microscopy. The treated fibers were then made into mats through a wet-laid process and compression molded with low density polyethylene via film stacking. The effects of different fiber treatment variables, including debundling time, on mechanical properties were compared with composites reinforced with conventional alkali treated fibers. The results presented show that the composites reinforced by hemp fiber using the new treatment method have equivalent or improved tensile, flexural and impact properties than the composite reinforced with alkali treated fibers.