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Full-Text Articles in Engineering Science and Materials
Experimental And Computational Failure Analysis Of Graphite/Bismaleimide Laminated Composite And Carbon Foam In Sandwich Construction, Troy C. Welker
Experimental And Computational Failure Analysis Of Graphite/Bismaleimide Laminated Composite And Carbon Foam In Sandwich Construction, Troy C. Welker
Theses and Dissertations
Sandwich beams consisting of a carbon foam core and graphite/bismaleimide face sheets were constructed and tested. Nine specimens were fabricated using three distinct cross-ply symmetric face sheet layups with a constant core thickness. Four-point bend testing controlled by a constant rate of midspan vertical displacement was used to load the specimens to failure. Displacements and strains from the experiment were compared to analytical sandwich beam theory and displacements and failure loads were compared to a layerwise finite element solution. A phenomenological failure criterion was developed that compares favorably with experimental failure data. The finite element solution gives failure within an …
Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness
Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness
Theses and Dissertations
During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Government and industry are looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to analyze poly-silicon MEMS devices made with the Multi-User MEMS Process (MUMPS trade name). Micro-Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. …
Reduction Of Thermal Residual Strains In Adhesively Bonded Composite Repairs, Heather R. Crooks
Reduction Of Thermal Residual Strains In Adhesively Bonded Composite Repairs, Heather R. Crooks
Theses and Dissertations
Many military and commercial aircraft are being called upon to fly well beyond their original intended service lives. This has forced the United States Air Force (USAF) to increasingly rely on structural repairs to address fatigue induced damage and to extend aircraft useful life. The focus of this research is the use of a high-strength composite patch technique to repair a fatigue crack on an aluminum aircraft structure. This study investigates the thermal residual strains that occur as a direct result of the coefficient of thermal expansion (CTE) mismatch between the repair patch and the underlying cracked metallic structure to …
The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic
The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic
Theses and Dissertations
This project compares the damping and fatigue life of bare titanium plates to those coated with magnesium aluminate spinel (mag spinel). Two different coating thicknesses were tested: .005" per side and .010" per side (total thicknesses of .010" and .020"). Dynamic ping tests were conducted on all specimens to determine their resonance frequencies. Laser vibrometry was used to determine the mode at each resonance frequency. Damping ratios were determined through the use of sine sweeps. A vibration mode was selected at which to fatigue the specimens, and the stress pattern was analyzed utilizing the Stress Pattern Analysis by Thermal Emissions …