Multifunctional sensor for simultaneous measurement of structureborne sound and vibration

Circular samples of Polyvinylidene Fluoride (PVDF) have been designed, fabricated, and tested to determine the feasibility of using this material as the active element of an inexpensive, multifunctional, co-located sensor array that can simultaneously measure strain and acoustic pressure. The custom electrode etching capability of PVDF, along with its ability to produce a linear response signal without the need of an external power source, makes this material very attractive. Custom etching allows many mechanical strain and acoustic sensors to be easily developed on the same film. This sensor system can then be used in structural noise and vibration control applications as well as damage detection applications. Feasibility tests were conducted in an anechoic chamber facility located at the University of Maryland. Sensor specimens of 28 micrometers and 52 micrometers thickness were tested using a loudspeaker and a calibrated condenser microphone. An analytical model describing the PVDF's plate response under acoustic loading was derived and illustrates the trend of the experimental data. Exact agreement between the analytical and experimental data is complicated because of the unknown cavity stiffness. This preliminary work suggests that a more refined model is required.