NASA 's Advanced Composites Project is investigating technologies that increase automated remote inspection of aircraft composite structures . Therefore , microwave Frequency Domain Reflectometry ( FDR ) is being investigated as a method of enabling rapid remote measurement of strain occurring at the first ply of a composite fiber reinforced polymer ( CFRP ) structure using Radio Frequency ( RF ) Electro - Magnetic ( EM ) radiation . While microwave reflectometry has been used to detect disbonds in CFRP structures , its use in detecting strain has been limited . This work will present data demonstrating the measurement of the reactance changes due to loading conditions that are indicative of strain in a CFRP structure . In addition , the basic EM signature will be presented along with an analysis of temperature and humidity effects .