Modeling and Analysis of Composites Using Smart Materials and Optimization Techniques

摘要

The vibratory load reduction at rotor hub using self-sensing piezoelectric material and closed loop control is investigated, A composite box beam theory is developed to model the primary load carrying structure in the rotor blade. In this theory, a higher order displacement field is used to model the individual walls of the composite box beam with surface bonded piezoelectric actuators. Based on these techniques, an integrated rotor vibratory load analysis technique is developed by coupling an unsteady aerodynamic model with the rotor blade dynamic model. A pole placement technique is used to design the control system for vibratory load reduction. Significant reductions are observed in the modal responses of the rotor with closed loop control. Next, the use of segmented constrained layer (SCL) damping treatment is investigated for improving helicopter aeromechanical and isolated rotor stability. A new laminate theory based on a hybrid displacement field is developed and is used to model the composite box beam with distributed SCLs. The rotor blade load-carrying member is modeled using a composite box beam. Ground and air resonance analysis models are implemented and the effect of both passive and active control in improving coupled rotor-body stability is investigated. In the passive study, a hybrid optimization algorithm is used to study the optimal placement of the SCLs along with composite tailoring. Significant improvements are observed in inplane modal damping. A control system is designed to effectively address the time- variant system and is shown to further improve aeromechanical stability of a hingeless rotor.