Enhancing the mechanical performance and thermal stability of natural fiber reinforced polymer composites through natural marine shell powder integration

Developing bio-composites from agricultural residues and marine-derived mineral waste at constituent proportions to achieve balanced mechanical, thermal, and moisture performance. This study investigated epoxy composites reinforced with KMnO 4 treated sugarcane bagasse (SUB) and banana peduncle (BAP) fibers, incorporating marine-based pyrum shell (MPS) derived bioceramic microparticles. Nine formulations (SHB1 to SHB9) were evaluated through mechanical, thermal, and water absorption tests. Within the investigated composition range, SHB6, comprising 20 wt% SUB, 15 wt% BAP, 4 wt% MPS, and 61 wt% epoxy showed the enhanced properties. It achieved a tensile strength of 19.98 ± 0.43 MPa, a tensile modulus of 2.97 ± 0.06 GPa, compressive strength of 64.15 ± 1.32 MPa, flexural strength of 49.61 ± 0.95 MPa, flexural modulus of 4.47 ± 0.09 GPa, and Charpy impact strength of 8.046 ± 0.145 kJ/m². Compared with SHB1, these values represented improvements of 58.70%, 110.64%, 45.53%, 76.93%, 144.26%, and 106.09%, respectively. SHB6 also recorded the lowest 168-h water absorption (2.84%) and the highest thermal decomposition onset temperature (328.0 °C). However, SHB5 exhibited greater absorbed impact energy (2.007 ± 0.115 J), highlighting property-specific performance differences. Higher formulations (SHB7 to SHB9) showed reduced mechanical performance and thermal onset stability, although residual mass increased to 22.4% in SHB9. Since fiber and filler contents varied simultaneously, the observed response represents a formulation-level effect rather than isolated constituent contributions. The findings establish a basis for further optimization through controlled mixture designs, interfacial characterization, and long-term durability assessment.