Date of Award

Spring 1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Engineering Mechanics

Committee Director

Chuh Mei

Committee Member

Norman F. Knight, Jr.

Committee Member

Brett A. Newman

Committee Member

Yong-Xiang Xue

Abstract

A feasibility study on the reduction of thermal deflection and random response of the composite structures using shape memory alloys (SMA) at elevated temperatures is presented in this dissertation. The characteristics of SMA are introduced and the structural problems, static and dynamic, of SMA fiber reinforced composites are investigated. The stress-strain relations are developed for a composite lamina with embedded SMA fibers. The finite element system equations including shape memory effect are derived. A consistent two-step solution procedure is developed for solving the static and dynamic problems of composite structures with embedded SMA fibers subjected to combined acoustic and thermal loads. With the consideration of nonlinear material properties of SMA and geometrically nonlinear deflection, an incremental technique and the Newton-Raphson iteration method have been employed to determine the static response of the SMA embedded composite structures.

Thermal buckling behavior of composite plates with and without embedded SMA has been studied first. The results show that the change of the austenite start temperature of SMA results in the increase of the critical buckling temperature of composite structures with embedded SMA. The study of thermal deflection of SMA hybrid composite structures has revealed that the thermal deflection can be reduced by changing the volume fraction, prestrain, austenite start temperature of SMA, as well as stacking sequence and boundary condition of structures.

The random response analysis of SMA hybrid composite structures indicates that the random response of composite structure with embedded SMA can be significantly reduced by combining proper percentages of SMA volume fraction and prestrain and also altering the austenite start temperature. Thus the benefits of using SMA will maintain the originally designed optimal aerodynamic efficiency at high temperatures during cruise and result in lower noise and longer service life.

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DOI

10.25777/5pde-tq63

ISBN

9780599208896

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