Characterization of Composite Material's Dynamic Response Using Load/Stroke Frequency Response Measurement Available to Purchase

A new experimental technique was developed to characterize damage development in composite materials. The technique does not require interruption of the test. It utilizes the frequency response measurement of load/stroke signals to characterize fatigue damage in terms of parameters such as phase and gain. Test frame and frequency dependency of the method was investigated. Center-notch quasi-isotropic unidirectional specimens were fatigue cycled at various load levels. From the fatigue test results, it was found that gain is related to the total damage and that phase may be related to the rate of damage in the specimen. Results also indicated that the method was sensitive to the applied load level and the material systems. This technique might be able to overcome problems involved in fatigue damage characterization of unidirectional laminates during high-temperature testing of composites where extensive splitting and elevated temperatures limit the use of extensometers.