Characterization of Creep in Polymer Composites by the Use of Frequency-Time Transformations

The use of frequency domain vibration test data to obtain time-dependent creep and relaxation properties of polymer composite materials is described. Frequency domain complex moduli are measured over a suitable frequency range by using vibration test techniques on small specimens. Complex moduli are then converted to time-domain relaxation moduli or creep compliances by using an Inverse Fourier Transform and numer ical integration. Several test functions were used to check the accuracy of the transfor mation, which was then used for characterization of an angle-ply graphite/polyimide composite.