Thermomechanical Buckling Response of Homogeneous and Functionally Graded Aluminium Beams Using Reddy’s Higher-Order Theory

This study aims to investigate the thermal buckling behaviour of thick homogeneous and functionally graded aluminiumbased beams using Reddy’s higher-order shear deformation theory. Recognising the limitations of classical and first-order theories in capturing shear effects and temperature-induced material degradation, a refined numerical model was developed to assess the stability of aluminium beams reinforced with Al2O3 and TiC under thermal loading. The material properties were assumed to vary through the beam thickness according to a power-law distribution, and temperature-dependent stiffness degradation is incorporated to mimic realistic high-temperature conditions. Three beam configurations, viz. a homogeneous aluminium beam, an Al-Al2O3 FG beam, and an Al-TiC functionally graded beam, were analysed over a temperature range of 30°C to 430°C and multiple gradation indices. The core novelty lies in the unified application of Reddy’s higher-order shear deformation theory combined with temperature-sensitive gradation to evaluate and compare the thermal buckling response across these three configurations. The results revealed a clear decline in critical buckling load with rising temperature across all cases. Functionally graded beams demonstrated superior buckling resistance compared to the homogeneous counterpart, with the Al-TiC configuration showing the highest critical buckling load values due to the high stiffness and thermal resilience of TiC. Among all gradation profiles, a lower power-law index (k = 1) emerged as optimal, offering up to 246% enhancement in critical buckling load. This work underscored the advantages of material gradation in enhancing thermal stability and validated the effectiveness of Reddy’s higher-order shear deformation theory in modelling thermomechanical instability in advanced composite beams. The insights gained can enhance the design of high-temperature structural components for aerospace, energy, and defence applications. Major Findings: The study proved that functionally graded beams reinforced with TiC demonstrated 246% more thermal buckling resistance than homogeneous aluminium beams. Optimal performance was observed at lower gradation indices (k = 1), where ceramic content near the compressive region enhanced stiffness. Reddy’s higher-order shear deformation theory proved effective in accurately capturing nonlinear shear effects and temperature-dependent material degradation.