Date of Award:

5-2018

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Advisor/Chair:

Ling Liu

Co-Advisor/Chair:

Thomas Fronk

Third Advisor:

Ryan Berke

Abstract

Composite materials are becoming popular in almost all industries. Carbon-fiber and glass-fiber composites are used in aircraft, sports equipment, boats, prosthetics, and wind turbine blades. In all these applications, the composites are subjected to different loads. Loads can take the form of impact or cyclic/fatigue loading, both of which decrease the strength of composites as micro-cracks grow through the composite. Composite laminates are made up of fiber plies (thin layers of fiber) and the fibers are surrounded by a resin like epoxy. It is common for laminates to fail because of delamination growth (plies peeling apart). Small delaminations do not fail a composite, but as delaminations grow, the composite weakens and eventually fails. Composites behave differently than metals do, and failure analysis is more complicated because of the various directions of fibers. Numerical methods (specifically Finite Element Analysis) exist for predicting when failure will occur, but improvements are needed to make these numerical methods more accurate and efficient. The method created, for this thesis, is computationally efficient because it doesn’t require the analyst or computer to adjust the simulation based on where the delamination is (or what kind of shape it is). Energy values are extracted directly from the delamination front and not averaged from nearby locations.

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