Date of Award


Degree Type


Degree Name


Degree Program



Mechanical Engineering

Major Professor

Hui, David

Second Advisor

Hall, Carsie

Third Advisor

Verges, Melody

Fourth Advisor

Schilling, Paul


This thesis discusses the effect of cryogenic temperatures on composite materials. The work includes estimating the shear strength of carbon/epoxy and glass/polyester composites at low temperatures and finding the rate of generation of microcracks in composites at cryogenic temperatures by acoustic emission technique. Microcracks increase the permeability of composites. So to study the permeability growth with microcracks, equipment is also designed to measure the permeability of composite to low temperature fluids. With short beam shear testing it was observed that the shear strength of composites increases with decreasing temperatures. Also carbon/epoxy composites were found to be much stronger than glass/polyester composites. Cryogenic temperatures improve the strength of composites but also generate microcracks in the structure due to the thermal expansion mismatch between the matrix and fiber. With acoustic emission testing from room to –150ºC, it was found that the rate of generation of microcracks increases with reducing temperatures. The work is extended to design a permeability equipment.


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