Determination of Vibration Parameters of Deformable Structures Using Different Dynamic Loading Schemes and Types of Fiber-Optic Strain Sensors

This paper presents several approaches for determining the vibration parameters of thin-walled deformable structures under different dynamic loading regimes using two types of fiber-optic strain sensors. The parameters considered include vibration amplitudes and frequencies, logarithmic decrements and strain mode shapes. The results are presented for a carbon fiber-reinforced polymer plate with nonstandard geometry. The measurements were performed using single-point fiber-optic sensors based on fiber Bragg gratings and distributed fiber-optic sensors based on Rayleigh scattering. The considered dynamic regimes included steady-state forced vibration and free vibration. Free vibration was initiated either by terminating steady-state excitation at a resonant frequency or by releasing the specimen from an initial static deflection imposed at different points. The experiments yielded strain amplitude–frequency curves under steady-state forced vibration based on measurements obtained with point and distributed fiber-optic sensors. The capability of distributed sensors to provide a spatial representation of strain, particularly the strain mode shapes, was demonstrated. The paper also presents resonant frequencies and logarithmic decrements determined for different types of dynamic response of the specimen.