Investigation on the Effects of Uncarbonised, Carbonised and Hybrid Eggshell Filler Addition on the Mechanical Properties of Glass Fibre/Polyester Composites

Waste eggshells were procured and processed to obtain uncarbonised eggshells and carbonised eggshells. Four variants of composites viz., unfilled, uncarbonised eggshell filled, carbonised eggshell filled and hybrid eggshell filled were fabricated using hand lay-up technique. All three variants of filled composites were added 10 wt.% of eggshells. The idea of hybridizing the uncarbonised and carbonised eggshell fillers was also carried out. A mechanical stirrer was utilised for mixing the eggshells with unsaturated polyester resin. All four variants of composites were subjected to tensile and flexural strength tests as per the respective American Society for Testing and Materials (ASTM) standards. The tests showcased that all eggshell filled composites possessed better tensile and flexural strengths compared to unfilled composites. Carbonised eggshell filled composites exhibited the highest strengths among all the composite variants considered, followed by hybrid composites and uncarbonised eggshell filled composites. The unfilled composites exhibited the least strength. The carbonised eggshell filled composites showcased 43.9 and 34.14% higher tensile and flexural strengths in comparison with unfilled composites. Microscopic analysis of the failed specimens was conducted using a scanning electron microscope (SEM). The SEM images revealed that the eggshell filler was responsible for crack deviations and crack arrests contributing to the strength of the composites.