## 4 Conclusions  
This study confirms tidal SSP as an effective, sustainable bio-filler for epoxy composites. Optimized SSP content improved density and hardness. Excessive loading reduced tensile strength due to agglomeration. EPA and EPB balanced mechanical and thermal properties, while EPB enhanced impact and tensile strength. These results support SSP-reinforced composites for cost-effective, sustainable applications in construction, marine, and automotive sectors. Future work should focus on advanced interfacial characterization, long-term durability testing, and exploring alternative bio-based resins to further improve performance. In this study, the potential use of a biologically derived material--namely, seashell waste, which poses environmental challenges but offers sustainable properties--as a reinforcement agent in epoxy-based composites was evaluated. Seashells were processed and ground into powder form, then incorporated into bio-based epoxy resin systems at varying concentrations. Using response surface methodology (RSM), the filler content and resin composition were optimized, after which the mechanical (tensile strength and impact resistance), physical (hardness and density), and thermal (thermal conductivity) properties of the resulting composites were determined through detailed testing. In addition, microscopic analyses were conducted to evaluate filler dispersion and the effectiveness \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Bulk Density**} & \multicolumn{3}{c}{**Shore D Hardness**} \\ \hline
**Std. Dev.** & 0.6045 & **R\({}^{2}\)** & 0.9945 & **Std. Dev.** & 0.0697 & **R\({}^{2}\)** & 0.9942 \\
**Mean** & 1140.36 & **Adjusted R\({}^{2}\)** & 0.9873 & **Mean** & 78.32 & **Adjusted R\({}^{2}\)** & 0.9866 \\ C.V. \% & 0.0530 & **Predicted R\({}^{2}\)** & 0.9584 & C.V. \% & 0.0890 & **Predicted R\({}^{2}\)** & 0.9604 \\  & & **Adeq Precision** & 40.3627 & & **Adeq Precision** & 38.9415 \\ \hline  & \multicolumn{3}{c}{**Thermal Conductivity**} & \multicolumn{3}{c}{**Thermal Degradation**} \\ \hline
**Std. Dev.** & 0.0005 & **R\({}^{2}\)** & 0.9919 & **Std. Dev.** & 0.5258 & **R\({}^{2}\)** & 0.9951 \\
**Mean** & 0.1078 & **Adjusted R\({}^{2}\)** & 0.9815 & **Mean** & 190.71 & **Adjusted R\({}^{2}\)** & 0.9888 \\
**C.V. \%** & 0.4508 & **Predicted R\({}^{2}\)** & 0.9515 & C.V. \% & 0.2757 & **Predicted R\({}^{2}\)** & 0.9696 \\  & & **Adeq Precision** & 53.3723 & & **Adeq Precision** & 45.9124 \\ \hline  & \multicolumn{3}{c}{**Charpy Impact Test**} & \multicolumn{3}{c}{**Tensile Strength**} \\ \hline
**Std. Dev.** & 0.0161 & **R\({}^{2}\)** & 0.9927 & **Std. Dev.** & 0.1752 & **R\({}^{2}\)** & 0.9902 \\
**Mean** & 2.6 & **Adjusted R\({}^{2}\)** & 0.9833 & **Mean** & 13.17 & **Adjusted R\({}^{2}\)** & 0.9879 \\
**C.V. \%** & 0.6201 & **Predicted R\({}^{2}\)** & 0.9515 & C.V. \% & 1.33 & **Predicted R\({}^{2}\)** & 0.9835 \\  & & **Adeq Precision** & 36.9542 & & **Adeq Precision** & 67.3688 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Statistical evaluation of experimental data and RSM model predictions. of matrix-filler interfacial bonding. The results of the characterization revealed that composites produced with optimal filler content exhibited enhanced performance in terms of hardness, density, and thermal stability while maintaining acceptable levels of mechanical properties such as tensile and impact strength. Microscopic observations showed that the seashell powder was homogeneously distributed within the matrix up to a certain filler ratio. However, exceeding this ratio led to microstructural defects such as agglomeration and porosity. These defects were found to negatively affect the overall performance of the composites by reducing the efficiency of interfacial bonding. In conclusion, this study demonstrates a promising approach for both promoting environmental sustainability through the valorization of marine waste and producing lightweight, durable, and cost-effective composite materials.