In this research, a sliding mode control (SMC) was utilized in the control of a partially treated, actively constrained layer damped (ACLD), Timoshenko beam model. The resulting vibration control was compared to the vibration control achieved by a state-feedback linear quadratic regulator (LQR) for several loading conditions. An observer was designed and model order reduction (MOR) was performed to achieve a simplified, efficient, and more controllable finite element system model. As a result of model simplification, modeling errors in the form of unstructured uncertainties were introduced into the system. It was determined that the SMC and LQR achieved similar vibration control for all loading conditions when saturation limits were imposed. The saturation limits were enforced to replicate realistic voltage constraints. Saturation limits were then removed to investigate the ideal control action of the SMC and LQR. The ideal case revealed that the SMC achieved a significant reduction in the maximum deflection and settling time (as much as 37.44% and 16.61%, respectively) for all loading conditions when compared to the LQR. The improvement in response was due to the increase in control activity and the utilization of a robust control scheme in the presence of unstructured uncertainties
