## 3 Results
### F-Ir  
The FT-IR spectra given in Figure 15 provide information about the physical and chemical structures and interactions between the epoxy resin and the seashell powder. Experiment 3, representing pure epoxy resin, exhibits characteristic peaks of epoxy groups, including absorption bands at approximately 915 cm\({}^{-1}\) (epoxy ring stretching), 1250 cm\({}^{-1}\) (C-O-C stretching), and 1500-1600 cm\({}^{-1}\) (aromatic ring vibrations). Additionally, a broad peak around 3200-3500 cm\({}^{-1}\) is present, which corresponds to hydroxyl (-OH) groups due  
Figure 14: SEM image of 3.5 g (7 wt.%) seashell-reinforced epoxy composite. Figure 13: SEM image of 1.75 g (3.5 wt.%) seashell-reinforced epoxy composite. to residual curing agents or slight moisture absorption. These peaks confirm the expected chemical structure of the cured epoxy resin. As the proportion of seashell powder increases in Experiment 7, Experiment 8, Experiment 10, and Experiment 4, notable spectral changes can be observed, particularly in regions associated with calcium carbonate (CaCO\({}_{3}\)). Seashell powder shows characteristic carbonate bands at 1400-1500 cm\({}^{-1}\) and 870 cm\({}^{-1}\). However, the main peaks of epoxy remain unchanged, indicating that the seashell powder does not chemically react with the epoxy matrix but is instead physically embedded within the polymer structure. A gradual increase in the intensity of the carbonate peaks is observed as the seashell content increases, which confirms its successful dispersion within the epoxy matrix. The physical interaction is further supported by the absence of new peak formations or significant peak shifts, suggesting that the composite formation is primarily governed by mechanical reinforcement rather than chemical bonding. Consistent epoxy absorption bands show the polymer network stays intact despite seashell filler. FT-IR analysis confirmed that ground seashell powder acts as an inert filler within the epoxy composite, modifying its physical properties without altering its chemical composition. This observation is consistent with a critical review where bio-epoxies showed similar inert behavior with shell-derived carbonate fillers, demonstrating minimal chemical interaction with the matrix [31]. The increasing intensity of carbonate peaks with higher filler content supports the uniform distribution of seashell powder. This suggests that the addition of seashells can enhance the material's mechanical performance, likely improving properties such as toughness and rigidity while maintaining the fundamental chemical  
Figure 15: FT-IR spectra of neat epoxy and powdered seashell-reinforced epoxy composites. characteristics of the epoxy resin. These results show that seashell powder can be effectively used as a bio-based filler in epoxy composites, offering potential environmental and economic benefits. The FT-IR spectra in Figure 13 are labeled with key functional group assignments, including characteristic epoxy C-O stretching (around 1100 cm\({}^{-1}\)), hydroxyl O-H stretching (near 3400 cm\({}^{-1}\)), and SSP-derived carbonate peaks (around 1400-870 cm\({}^{-1}\)). The presence of these bands confirms the incorporation of SSP while maintaining the expected functional groups of the epoxy matrix. The absence of new peaks or significant shifts indicates no unexpected chemical reactions between SSP and the epoxy system, supporting the conclusion that SSP acts as an inert, physically reinforcing filler. This analysis confirms the compatibility and stability of the bio-filler within the composite structure. The correlations between the experimental results and the predicted values derived from the RSM model are presented in Figure 16. Each subplot (a-f) compares actual versus predicted values for key material properties, including bulk density, Shore D hardness, thermal conductivity, thermal degradation, Charpy impact strength, and tensile strength.