Optimization of physical and hardness properties of epoxy composites reinforced with Meretrix lusoria Shell particulates using RSM

Abstract

Epoxy composites are essential in marine, automotive, and aerospace applications but face challenges of high cost and limited sustainability due to reliance on synthetic reinforcements. Meanwhile, marine waste such as Meretrix lusoria shell (MLS) poses a significant environmental challenge due to disposal issues, yet contains calcium carbonate suitable for reinforcement. This study explores the optimization of physical and hardness properties of epoxy composites reinforced with MLS particulates, a marine waste material. MLS was processed into particle sizes ranging from 75 to 600 μm, and density, water absorption, oil absorption, thickness swelling, and hardness were evaluated. Results revealed that larger particles increased density (up to 1.72 g/cm3 ), water absorption (1.43 %), oil absorption (0.68 %), and swelling (14.5 %), while hardness decreased from 92 HRC (75μm) to 74 HRC (600 μm). ANOVA confirmed the statistical significance of particle size (p < 0.05). Numerical optimization identified 378.916 μm as the optimum particle size, predicting balanced properties of 1.647 g/cm3 density, 1.186 % water absorption, 0.472 % oil absorption, 11.879 % swelling, and 80.765 HRC hardness. Validation tests showed <5 % error, confirming model accuracy. These results highlight the trade-off between strength and absorption, and demonstrate MLS waste as an effective, sustainable reinforcement for high performance epoxy composites in marine, automotive, and aerospace applications