Date of Award

7-2017

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. Ali Y. Tamijani

First Committee Member

Dr. Marwan Al-Haik

Second Committee Member

Dr. Frank Radosta

Abstract

The purpose of this research is to explore the design of variable stiffness composites and develop an automated framework to model, analyze and optimize these structures. Variable stiffness composites have been shown to exhibit increased strength and stiffness over traditional constant stiffness composites by tailoring fiber orientations for specific load conditions. This is achieved by allowing the fiber orientation to vary spatially across the design domain. Motivation for new design methods is driven by the recent advancements in composite additive manufacturing, such as automated fiber placement machines, which allow fiber reinforcements to be placed along prescribed trajectories during manufacturing. Through this research the problem of optimized orthotropic material orientation will be investigated. A new methodology is proposed that uses the concept of structural load flow to determine fiber trajectories. Fiber designs using the load path method are compared to the classical approaches such as the strain, stress, and energy methods. The load path function method is also expanded upon to solve the problem of non-homogenous equilibrium equations. This method allows load paths to be determined for more complicated loads such as aerodynamic pressures, thermal and inertial loads. Additionally, the design considerations for 3D printed composites are addressed. Experimental validation of the finite element codes used to model 3D printed composite structures is presented.

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