Enhanced mechanical and thermal properties of polyester/glass/sheep wool fiber hybrid composites by successful replacement glass with wool

This study aims to examine the possibility of partially substituting glass fiber (GF) with sheep wool fiber (SWF) with the goal of developing environmentally sustainable hybrid polyester composites. This study investigated the mechanical properties (tensile, flexural, and impact), thermal properties, water absorption, and microstructures of hybrid composites. The targeted composites were fabricated via compression molding and contained a total fiber weight fraction of 10% (with varying proportions of GF and SWF). Initially, the surface chemistry, morphology, tensile properties, and thermal stability of SWFs were analyzed individually. In the case of the composites, the highest tensile strength was recorded for the 9GF1SWF (comprising 9 and 1 wt% GF and SWF, respectively) hybrid composite, which reached 14.09 MPa (7.31% higher than 10GF0SWF). The 9GF1SWF sample also presented the highest amount of absorbed flexural energy prior to failure, 166 MJ/m³ (19.42% higher than 10GF0SWF), and the highest impact strength, 11.15 kJ/m² (11.05% higher than 10GF0SWF). The TGA results revealed that the incorporation of SWF reduced the rate of thermal degradation as well as improved thermal stability of the hybrid composites, especially at high temperatures. The microstructural characteristics of the composites and their correlation with the mechanical properties, along with the various reinforcing mechanisms, were examined through scanning electron microscopy (SEM). In terms of water absorption, both the hybrid and polyester/glass composites exhibited comparable behavior, with similar absorption levels. In brief, the findings of this study suggest that sheep wool fibers may serve as a viable alternative to synthetic glass fibers.