Investigation of the Mechanical Properties of Epoxy Matrix Composites Reinforced with Stellite 21 at Different Sizes

Increasing performance requirements in engineering applications have led to a growing demand for materials that simultaneously provide high mechanical strength, wear resistance, low density, and cost-effectiveness. In this study, the mechanical and microstructural properties of epoxy matrix composites reinforced with Stellite-21 particles were investigated. Composite specimens were fabricated using Stellite-21 metallic powders with particle sizes of 60, 75, and 125 µm at weight fractions ranging from 0.10 to 0.40 wt.%. Shore D hardness, tensile, three-point bending, and Izod impact tests were conducted to characterize the mechanical behavior of the specimens, and the fracture surface morphologies were examined using Scanning Electron Microscopy (SEM). Furthermore, SEM micrographs were semi-quantitatively analyzed using ImageJ software to evaluate particle distribution, void formation, and interfacial defects. The mechanical test results were statistically evaluated using one-way analysis of variance (ANOVA). The results showed that the incorporation of Stellite-21 increased the elastic modulus and hardness of the epoxy matrix; however, higher filler contents and larger particle sizes resulted in a reduction in tensile, flexural, and impact strengths due to interfacial defects and void formation. The optimum mechanical performance was achieved at low filler contents and smaller particle sizes. These findings indicate that reinforcement parameters should be optimized together with the matrix type to achieve superior composite performance.