Resonance technique, elastic properties

Inevitably, the conjunction of frequency-dependent visco-elastic properties and wave propagation leads to consideration of visco-elastic wave dispersion and its influence on conventional wave-based measurements, such as those involving resonance phenomena and pulse propagation techniques. 

Several nanomechanical characterization techniques have been suggested to measure the elastic properties of individual electrospun nanofibers, such as AFM cantilevers, universal tensile tester, and AFM-based nanoindentation system [133, 134]. Among them AFM-based techniques have been widely used to measure the mechanical properties of single electrospun nanofibers. This technique was carried out by attaching nanofiber to two AFM cantilever tips and recording the cantilever resonances for both the free cantilever vibrations and for the case where the microcantilever system has nanofibers attached. The Young s modulus of the nanofiber is then derived from the measured resonant frequency shift resulting from the nanofiber. A similar experiment has been carried out for electros-... 

Resonance techniques have been extensively used to find polymers with high loss factors, for sound absorption and vibration-damping applications, and to determine relations between acoustic and elastic properties and molecular composition and morphology. 

The data presented here have excluded nematic polymer liquid crystals. These present particular difficulties for the conventional methods of measurement, which require well-aligned samples. A magnetic resonance technique has been developed which is particularly suited to the measurement of the elastic and viscous properties of liquid crystalline polyma s, and this technique and specimen results are described in Datarevicw 8.3 in this volume [40]. Thore have been some measurements on the precursors to polymers i.e. dimers and trimers (see Section C3), and these limited results do indicate the importance of molecular shape in determining the elastic properties. In particular, the extended even dimer has elastic constants almost twice those of the bent odd dimer. Thus in polymer liquid crystals, it is clear that the chain configuration will have a dramatic influence on the elastic properties. 

The particular choice of the authors was rather to put emphasis on experimental techniques that are either specifically relevant or powerfiil with respect to ferroelectric polymers and fenoelectrets or represent recent experimental developments and trends. In this sense, room was given to nonlinear dielectric properties that can be probed by nonlinear dielectric spectroscopy and various types of hysteresis experiments. Besides a systematic description of piezoelectric and inverse piezoelectric techniques, we have added dielectric resonance spectroscopy as an all-round approach yielding elastic, piezoelectric, and dielectric properties of polymer electrets in a single dielectric measurement. 

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