Performance of Sisal/Hemp Bio-based Epoxy Composites Under Accelerated Weathering

The biocomposites were produced by layering sequence of pure sisal fiber mat (SSSS), pure hemp fiber mat (HHHH), and their hybrid mats and then subjected to accelerated weathering conditions. The composite specimens were conditioned under ultraviolet (UV) light and water spray simultaneously for 2222 h, which corresponds to approximately 1 year of the outdoor conditions. Mechanical properties and thermogravimetric analysis (TGA) of the weathered composites were compared to the dry or unweathered composites. Chemical changes to the bio-based epoxy matrix and natural fiber induced by photodegradation were evident as a reduction in intensity and broadening of characteristic peaks from the Fourier Transform Infrared spectroscopy (FTIR) analysis. Tensile strength and flexural strength of the weathered HSSH and HSHS declined by 7%, 13%, 25%, and 26%, respectively. Degradation effects of weathering were also visible from the lower residue of the weathered composite specimens from the thermogravimetric analysis. Despite the slight drop in impact strength, all the weathered composite specimens had good impact resistance. Furthermore, the hybrid composites exposed to weathering had nearly equivalent impact strength compared to the pure sisal and hemp-based composites under the impact load. Based on this observation, sisal/hemp fiber bio-epoxy based hybrid composites are recommended for the outdoor structural applications requiring impact resistance.