Using Electrochemical Impedance Spectroscopy as a Non-Destructive Evaluation Technique for Advanced Polymer Matrix Fibrous Composites

Initial investigations have been conducted to determine the applicability of using Electrochemical Impedance Spectroscopy (EIS) as a non-destructive evaluation (NDE) technique for advanced polymer matrix fibrous composites.  The fibrous composites of interest include phenolic matrix/S-glass fiber, and phenolic matrix/Kevlar® fiber both of which are used in armoring applications for military ground vehicles.  EIS is a suitable NDE technique as it is a fast measurement that outputs quantitative results that are not common in several accepted NDE techniques of composite materials.  Circuit modeling of the EIS spectra is another integral aspect of using EIS as the elements of the system can be monitored with time to determine what aspect of degradation may be causing the changes in the material, as well as to what extent. 

Accelerated ultraviolet radiation conditions were introduced to the specimens to initiate delamination and void creation.  The intimate bond between the fiber and matrix is the inherent aspect of composites which allows for load transfer to occur efficiently; therefore, creation of these delaminations and voids from exposure often cause these types of materials to lose their mechanical and ballistic integrity among several other properties and characteristics.  Research of the correlation between constituents of the circuit modeled spectra of an EIS measurement, mechanical, and ballistics properties as a function of the weathering time is simultaneously being performed.