Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering and Applied Mechanics

Department

Mechanical, Industrial and Systems Engineering

First Advisor

Arun Shukla

Abstract

The effects of long term exposure to a sea-floor depth ocean environment on the mechanical behavior of carbon-fiber / epoxy (CFE) laminated composites were investigated experimentally. A novel high pressure accelerated aging facility was designed and fabricated for the express purpose of performing accelerated life testing. This facility utilized an elastomeric diaphragm capable of transferring hydraulic oil pressure to a saline water filled volume in order to create a simulation of a deep ocean environment, to which specimens were exposed at elevated temperatures in order to accelerate the rate of water ingression from real world time scales of years to laboratory exposure times of mere days. Utilizing this facility and the Arrhenius relationship for diffusion of water into a polymer matrix composite, the factor of acceleration was determined to be 0.64 years of actual service equivalent to a day of laboratory time at 70 °C. CRE specimens were aged for time periods representing 0 (unweathered), 8.9, and 15.3 years of service. Quasi-state testing revealed no significant degradation of in-plane tensile or shear properties yet 13.8% and 20.1% reduction in flexural modulus for the two weathering cases, respectively. Air-blast response was evaluated using a shock-tube apparatus coupled with high frequency response pressure measurement of the shock wave and digital high speed stereo photography. Utilizing the 3D digital image correlation technique and an impulse based normalization procedure, the normalized out-of-plane deflection of the beam did not significantly change with weathering.

Available for download on Sunday, May 16, 2021

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