Date

2018

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Mechanical Engineering

First Adviser

Grenestedt, Joachim L.

Abstract

The need for faster and more accurate manufacturing methods for composite parts continues to grow. Co-curing composite structures can decrease manufacturing time by eliminating secondary operations such as grinding, jigging, bonding, and fastening while creating lighter and more accurate parts. As a demonstrator for co-curing techniques, a six-meter carbon fiber wing for a high-altitude and high-speed dynamically soaring unmanned aerial vehicle (UAV) was designed and manufactured in one cure cycle. Two wing-skin molds were created using low density tooling board, with the mold geometry directly machined into the material, reducing tool manufacturing time and cost. An aluminum insert was used to create a trailing edge cavity while maintaining a simple parting line of the wing tool. Three removable forms made of polystyrene foam inside of the wing cavity were used to position six internal webs and, after curing and removal of the forms, resulted in a hollow wing with internal webs. The resulting wings showed some defects in the wing skins but overall produced structurally sound parts.Expanding on the previous co-curing techniques, a 1.1-meter carbon fiber horizontal stabilizer with internal structure and an elevator connected by a composite flexure was designed and manufactured in one cure cycle. The stabilizer is used in a high-altitude and high-speed dynamically soaring unmanned aerial vehicle (UAV). The top skin is used as the flexure, creating a seamless top surface between the stabilizer and elevator. Three removable forms made of polystyrene foam were used inside the stabilizer to position a spar web and center rib, which after curing and removal of the forms resulted in a hollow stabilizer with an internal web and rib. The resulting stabilizers showed minor defects in the wing skins but overall produced structurally sound parts.The demonstrators showed the great potential for creating complex composite parts and assemblies using only a single cure cycle while needing little finishing work and no secondary bonding, resulting in high precision at relatively low cost.Utilizing the components produced, the JetStreamer was able to be assembled and flown in Weldon, The JetStreamer is believed to be the largest unmanned aircraft to demonstrate dynamic soaring.

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