Energy transfer across cracks in a thin membrane strip

This paper presents recent results from an ongoing investigation on the use of non-collocated actuator/receiver pair to enable dynamic testing of a thin membrane in order to detect cracks. The current focus is on obtaining the transfer function of a Kapton membrane excited at one end by a polyvinilidine fluoride (PVDF) actuator. A receiver of identical specifications is located at the other end. The actuator operates in the d31 mode which under sinusoidal excitation leads to a periodic variation in membrane tension. The paper shows that the resulting dynamics can be analyzed with the help of the Mathieu equation. As such, the frequency response of this membrane is complicated. The presence of a crack could in principle be detected by the corresponding decrease in the output voltage amplitude at the drive frequency in the Fourier transform of the output, but this was found difficult in practice. Detailed analysis of the parametrically excited dynamics with and without a crack could lead to precise and reliable signatures for healthy and cracked membranes.