This study presents a comprehensive investigation into vibration suppression of delaminated smart composite beams integrated with surface-bonded piezoelectric (PZT) actuators. A finite element framework utilizing ANSYS APDL was employed to model the modal, harmonic, and transient responses of cantilever beams under varying delamination conditions and control strategies. Closed-loop feedback vibration control with displacement signals was implemented through proportional–integral–derivative (PID) schemes, and the effects of individual control gains (Kp, Ki, Kd) were systematically examined. The results indicate that while proportional feedback control significantly improves damping and reduces rise time by over 40%, the integral and derivative components contribute minimal additional benefits. Modal analysis confirmed the optimum actuator voltages for vibration suppression, with double-patch PZT configurations demonstrating approximately 30% lower control voltage compared to single-patch arrangements, thereby enhancing energy efficiency. Transient analyses further revealed up to 85% reduction in steady-state vibration amplitude in delaminated laminates, affirming the efficacy of displacement feedback control. Overall, the findings establish proportional control in combination with optimally placed PZT patches as a practical, energy-efficient, and robust solution for active vibration mitigation in smart composite beams, even in the presence of structural delamination.