The use of polyvinylidene fluoride films as sensors for the experimental modal analysis ofstructures

Abstract

This work presents the use of a rectangular shape of PVDF (polyvinylidene fluoride) filmadhered on the surface of a cantilever beam and a simply supported plate as the sensor,while the impact hammer is applied as the actuator for the structural modal testing. Thiswork first formulates the frequency response function (FRF) based on the hammerexcitation and PVDF sensing. The hammer actuator eigenfunction and the PVDF sensoreigenfunction can be identified as the displacement mode shape and the mode shape of theslope difference between the PVDF edges, respectively. A dual-channel FFT analyzeris used to perform the experiments. A row of the FRF matrix can be obtainedwhen the PVDF sensor is roving with the hammer actuator fixed. The MDOFcurve-fitting algorithm is used to extract the modal parameters, including naturalfrequencies, mode shapes and modal damping ratios of the structures. The frequencyresponse functions are shown to agree reasonably well between theoretical andexperimental results. Results also show that modal parameters can be properlyobtained and physically interpreted with theoretical solutions. This work, therefore,demonstrates the feasibility of using the PVDF sensor in conjunction with thehammer for structural modal testing and can also be extended to other structures.