Doctoral Dissertations

Date of Award

12-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Mechanical Engineering

Major Professor

Stephanie TerMaath

Committee Members

Reza Abedi, Madhu S. Madhukar, Russell Zaretzki

Abstract

The interest in the application of high strength aluminum alloy in marine structures has been increasing in recent years due to its high strength-weight ratio and excellent corrosion resistance. However, those marine grade aluminum alloy unavoidably experience fatigue and stress corrosion cracking during their service life. Developing a reliable repair method is essential to address the damage problems. The composite patch has been demonstrated as a promising method to repair the damaged or reinforce the under-designed aluminum structures. This research focuses on creating a comprehensive understanding of damage mechanisms involved in the composite patch repaired structures. The compact tension testing of aluminum, four-point bend and fracture testing of composite repaired structures are employed to investigate the yielding and cracking in aluminum, fiber breakage, matrix cracking and delamination in the composite patch, and disbond of the bond line. The validated, high-fidelity 3D finite elements are developed to simulate those damage mechanisms. The sensitivity analysis coupling with the finite element simulations is then performed to study the effects of different damage modes and their interactions on the ability of the composite to restore the load capability of repaired structures. The most and least important factors affecting different damage modes are identified to reduce the design space, which enables the improvement of the design efficiency of the composite patch.

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