Appraisal of inorganic and lignocellulosic organic shell wastes as a green filler in epoxy-based hybrid composites

Hybrid composites are now becoming increasingly important regarding economic and ecological compatibility. This study presented the research results that evaluate the feasibility of using cherry pit shell (CPSh) and chicken eggshell (ChESh) natural wastes as a new hybrid filler mixture for the first time. CPSh and ChESh can reduce the composite material cost and increase the biobased content. CPSh was treated with a 5 % NaOH alkali solution to enhance the lignocellulosic filler-matrix interfacial interaction. Hybrid green organic and inorganic fillers were used in the epoxy matrix (ER). Morphological, water absorption, thermal, and mechanical performance of hybrid composites were investigated. The tensile strength of ER increased max. by 5.73, 7.3, 17.98, and 14.27 % in the case of raw CPSh, ChESh, and hybrid filler mixtures at 1:1 and 1:3 wt mixing ratios of alkali-treated CPSh (NaOH-CPSh) and ChESh, respectively. The composites' thermal stability and dynamic-mechanical properties in different aging environments (seawater and hydrothermal) were examined by thermogravimetric analysis (TGA) and dynamic-mechanical analysis (DMA). Hydrothermal was the most affected aging condition on the composite properties. In addition, ANOVA is applied to find the significant effect of different weight percentages of hybrid fillers on the mechanical properties of composites.