This research presents a comprehensive thermal and structural evaluation of a newly developed aluminium matrix composite reinforced with selected agricultural by-products—palm kernel shell, bamboo fibre, rice husk, and groundnut shell—using Finite Element Analysis (FEA) within the ANSYS 2025 environment. Aluminium scrap served as the matrix material in the composite fabrication. The experimental design followed a D-Optimal mixture approach, yielding twenty-five specimen combinations, each tested thrice, with mean values recorded. Specimen fabrication employed the stir casting technique. Optimization of process parameters and response outcomes was performed using Design Expert software. The composite model was developed using SOLIDWORKS for subsequent simulation analysis. Results from the thermal and structural simulations indicate a fatigue life of 1 × 10⁶ cycles. The computed maximum and minimum total heat fluxes were 1.8122 × 10⁶ W/m² and 1.515 × 10⁶ W/m², respectively, while the fatigue damage factor reached 1000. The safety factor varied between 4.836 and 15. Temperature values ranged from 23.685°C to 170.000°C. The composite exhibited equivalent elastic strain values between 1.054 × 10⁻⁶ and 2.9051 × 10⁻⁵. Directional deformation along the x-axis ranged from –2.5905 × 10⁻⁷ m to 2.5889 × 10⁻⁷ m. Equivalent (Von-Mises) stress was recorded between 1.3224 × 10⁵ Pa and 5.8104 × 10⁷ Pa, while total deformation ranged from 0.0000 m to 2.5912 × 10⁻⁷ m. These findings underscore the mechanical and thermal reliability of the developed composite material for engineering applications under variable thermal and mechanical loads.