The mechanical properties of different polymer matrix composites are discussed in this research study. These composites are multiphase materials in which reinforcing elements and a polymer matrix are suitably combined. The mechanical properties of 18 PMCs, including nylon 66 reinforced with 5, 15, and 25% wt% silicon carbide (SiC) and nylon 66 reinforced with 5, 15, and 25% wt% boron carbide (B4C), were evaluated using an injection moulding technique at three different injection pressures in this study. The optimization of process parameters like reinforcement material, reinforcement quantity, and injection pressure to maximize the tensile and impact strength of nylon 66 composites are the main focus of this study. It is observed that the specimens 25% SiC with an injection pressure of 90 MPa has optimised tensile strength, while the specimen 5% B4C with an injection pressure of 90 MPa has optimised impact strength.