Date of Award

6-1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Brad S. Liebst, PhD

Abstract

A method for the simultaneous structural and control optimization for torsional vibration of a composite plate which simulates a spacecraft solar array structure was developed in this study. Included in the optimization of the plate are the location of the piezoceramic actuators and sensors that provide bending/torsion actuation, the control gains, and the orientation of the graphite fibers in the composite plies. This research included the effects of using composite tailoring to promote the coupling of the twisting-bending mode to enhance the damping system. The plate was modeled by classical lamination plate theory using a linear elastic strain-displacement theory. This theory was then incorporated into a performance index which contains both structural and control parameters that minimizes torsional and bending motion at the tip of the plate due to a torsional force at the tip. Along with the performance index, there are inequality constraints on the amount of power to the actuators. This performance index and constraints, along with upper and lower bounds on the design variables, were incorporated into an optimization subroutine which then produced an optimal design for controlling both torsional and bending vibration. This optimal plate was fabricated and tested with a torsional load to decide the validity of the theory in improving damping. A comparison was made between the results of the theory and the experimental results of testing the optimized plate and a baseline plate made up of a quasi-isotropic lay-up. The frequencies of the experimental and the theoretical results were within 15% of each other. Also the damping factor for the 1st torsional and 2nd torsional modes of vibration increased significantly for the optimized plate versus the baseline plate which verifies the basic premise of the theory.

AFIT Designator

AFIT-DS-ENY-96-8

DTIC Accession Number

ADA310755

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