Date of Award

6-11-2007

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Robert Canfield, PhD

Abstract

Structural weight and efficiency are hurdles for morphing aircraft being realizable on the full-scale level. The optimal distribution and orientation of actuators throughout an in-plane flexible morphing wing structure is investigated. The drive to minimize structural weight causes a wing to be more flexible and the location and orientation of the actuators become more critical as the structure becomes more flexible. NextGen's N-MAS morphing wing is used as a case study. The wing is modeled as a number of unit cells assembled in a scissor-like structure, each comprised of four linkages pinned together and an actuator. The flexible skin of the wing is modeled with a nonlinear material stretched between two opposing vertices. It will be shown that the optimal orientation of the actuators will vary depending on the loading conditions and initial configuration of the wing. Sequential quadratic programming (SQP) optimization techniques are utilized to orient those actuators and effectively size the members of the structure. The goal is to minimize weight while maximizing the geometric advantage and efficiency. The constraints are member stresses and the force transferred to the actuators is not to be greater than the force the actuator is able to produce. Matlab® code is developed to do the SQP optimization while NASTRAN™ is utilized to do the nonlinear finite element analysis required to evaluate the objective function and constraints. The single-cell results are compared to experimental data to validate the finite element model (FEM) and optimization routine. A three-cell experiment is designed by utilizing aeroelastic scaling techniques. Matlab is used to develop the scaling problem while the actual scaling is done as an optimization in NASTRAN. The objective for scaling the wing is to minimize the differences in the non-dimensional displacements and strain energies between the two models, using the element cross-sectional dimensions as design variables.

AFIT Designator

AFIT-GAE-ENY-07-J22

DTIC Accession Number

ADA470137

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