Date of Award

12-2001

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Dr. Eric v. K. Hill

Committee Member

Dr. Frank J Radosta

Committee Member

Dr. Ronnie K. Miller

Abstract

Cost savings can be achieved in a wide range of applications by replacing the current procedure for hydrostatic recertification of high-pressure composite gas cylinders with acoustic emission (AE) nondestructive testing. Advantages of AE recertification over the current hydrostatic method include: (1) no water contamination, since pressurization of the cylinders is done with air as opposed to water; (2) the risk of damage is decreased since the test pressure is reduced from 166% of design pressure to 110% of operating pressure; (3) the ability of acoustic emission to detect and locate flaws increases safety; and (4) the in-situ method will reduce cost and downtime.

A method for testing of filament-wound composite pressure vessels has been proposed by the draft ASTM standard E07.04.03-95/1 (Standard Test Method for Examination of Filament-Wound Composite Pressure Vessels Using Acoustic Emission). The research presented follows the proposed acoustic emission technique and shows results that validate the draft ASTM standard in the case of aluminum-lined graphite/epoxy Type 3 vessels.

Over a period of several months, pressure cycling, controlled impact damage, and controlled chemical attack were used to degrade the structural conditions of several pressure vessels in a fashion representative of service-induced damage. Once the cylinders had been subjected to a known amount of damage and cycling, they were pneumatically pressurized and monitored with AE during the pressurization cycles. The results from the AE monitoring are reported herein. Finally, AE data from the pressurization tests were correlated with the associated damages, and a level of AE activity that corresponds to a damaged bottle was defined.

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