Date of Award

2001

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Vincent Caccese

Second Committee Member

Donald A. Grant

Third Committee Member

Christine Valle

Abstract

Carbon fiberlcyanate ester matrix composite panels with bolted connections to aluminum endplates were tested in four point bending at room and elevated temperatures. The specimens tested were subcomponents of the NASA X-38 Crew Return Vehicle. The X-38 is the proposed escape vehicle for the International Space Station, currently being constructed in Earth orbit. During reentry into the Earth's atmosphere, the composite aeroshell of the X-38 is expected to experience elevated temperatures, which makes accurate characterization of material properties at elevated temperature imperative to a sound design. Three varieties of specimens were tested: flat composite laminates, hat-stiffened composite laminates, and sandwich construction composite panels. Instrumentation was used to collect displacement, strain, load, and temperature data. The data were then used to characterize the effects of the elevated temperature environment on the stiffness, strength, and failure modes of the composite material. After inspection of the results, the elevated temperature environment had a marked effect, lowering the stiffness and ultimate load capacity of the hat-stiffened and sandwich panels. The modes of failure for the hat-stiffened laminates were highly temperature dependent, while the effects of elevated temperature on the failure modes for the sandwich panels was not apparent from the data. A simplified beam analysis, using strength of materials beam theory, was undertaken to characterize the joint stiffness in the room temperature experimental set-up. Results indicated a good correlation between the experimental deflected shape and the predicted deflected shape of the flat composite laminates, hat-stiffened laminates, and the composite sandwich panels.

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