This work presents a vibration and dynamic stability analysis of rotating functionally graded porous (FGP) shafts using Timoshenko beam theory (TBT) combined with the \(p\) -version finite element method ( \(p\) -FEM). The formulation simultaneously captures shear deformation, rotary inertia, gyroscopic coupling, rigid disk inertia, and linear bearing stiffness/damping, while explicitly modeling both symmetric and non-symmetric porosity distributions in the shaft. Material gradation and porosity are represented through continuous radius-dependent variations of Young’s modulus, shear modulus, and density, calibrated to the effective behavior of open-cell metallic foams. Convergence studies and comparisons with benchmark solutions for homogeneous beams, FGP cylindrical shafts, and rotating shafts confirm the accuracy and robustness of the model. Using Campbell diagrams and extensive parametric studies, the proposed framework systematically quantifies how porosity level and pattern, geometric slenderness/thickness ratios, and support stiffness and damping jointly affect natural frequencies, forward/backward whirl separation, and critical speeds. The results reveal that symmetric porosity can enhance the effective stiffness-to-mass ratio and thereby improve dynamic stability, whereas non-symmetric porosity consistently degrades it. Additionally, stiffer bearings, lighter disks, and high-modulus ceramics increase critical speeds, while strong external damping reduces them. The findings provide practical guidelines for tailoring porosity patterns, geometric parameters, and support conditions in lightweight, high-speed FGP rotors for aerospace, power generation, and advanced turbomachinery applications.
