Vibration Response and Damage Detection of Carbon/ Epoxy Beams at Elevated Temperatures using the Hilbert-Huang Transform

The vibration response from undamaged and damaged polymer matrix composite beams at elevated temperatures is analyzed using the Hilbert-Huang Transform (HHT) technique. The HHT shows potential in identifying the nonlinear damaged response of the beams. Using empirical mode decomposition to separate superposed modes of signals, several intrinsic mode functions can be determined which can reveal more information about complex nonlinear signals than traditional data analysis techniques such as the Fourier Transform. The composite beams are fabricated from an out-of-autoclave uniaxial carbon/epoxy prepreg (CYCOM™-5320-1/T650). Delamination damage in the composite layups is introduced by insertion of mold release wax films during fabrication. A shaker-table fixture was used for the vibration testing of all beams in a vertical cantilever configuration. High temperature piezoelectric accelerometers were used to obtain the vibration data for a frequency range of 1-61 Hz. This study investigates the effect of damage on the measured vibration data using intrinsic mode functions and Hilbert Huang spectrums.