Date of Award


Degree Type


Degree Name


Degree Program



Mechanical Engineering

Major Professor

Verges, Melody

Second Advisor

Herrington, Paul

Third Advisor

Schilling, Paul


The application of an ultralight linerless composite fuel tank to a man-rated, reusable launch vehicle requires greater understanding of the micro-fracture behavior which can lead to propellant permeation through the tank wall. Transverse matrix cracks in unidirectional wound, or placed, plies can provide a path for permeation of pressurized fluid if the cracks interlink from the interior to the exterior of the tank wall. Following research on an energy based fracture mechanics approach to composite microcracking, experiments in fatigue were run on IM7/977-2 cross-ply laminates. Using a modified Paris Law approach, microcracking fatigue data is presented over a wide range of applied cyclic stresses. This Paris Law plot shows an "A" value of 6.40x10-25 and a "B" value of 8.07 and provides a complete characterization of composite IM7/977-2 material's resistance to microcrack formation during fatigue loading.


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