Application of electrochemical impedance spectroscopy as a non-destructive technique to characterize and detect degradation of carbon/nylon, 6 composites in aqueous environments

Experiments were conducted to investigate the degradative effects of ambient and high pressure aqueous environments on unidirectional carbon fiber nylon (AS4/nylon 6) composites. Electrochemical impedance spectroscopy (EIS) was selected for development as a non-destructive method to characterize the degradation phenomena in carbon/nylon composites as result of moisture absorption. EIS data was collected for composites and neat resins as a function of immersion time in ambient and pressurized (6.2 MPa) 3.5% NaCl solution. EIS was also utilized to understand degradative mechanisms when composites were subject to cathodically induced damage. Concurrent EIS and 3-point mechanical loading was also performed on composites to study the changes in the impedance response as a function of loading. A detailed equivalent circuit analysis is also presented in an attempt to elucidate the degradation phenomena in composites. Gravimetric and 3-point mechanical testing data is also presented to study the effect of ambient and pressurized aqueous environments on composites. Scanning electron micrographs of composites are also included to assist in morphological evaluation.