Laser Doppler vibrometer and bending wave based dynamic material characterization of organic aerogel panels

Abstract

To what extent aerogels are useful in noise and vibration control applications remains an open question. With the advent of low cost, facile synthesis, ductile, and purely polymeric aerogels, the prospects are alluring. Within the polyurea family of aerogels, multiple nanomorphologies exist with some being amenable to rheological paradigms. An inverse problem approach is applied to tease out material parameters with the aid of viscoelastic models and a pair of dynamic characterization techniques. A specialized transfer function driven, quasi-longitudinal wave eliciting, material characterization setup is refined and augmented with laser Doppler vibrometry. This effort seeks to improve repeatability and increase frequency limits, two factors whose absences plague many schemas. Intriguing properties previously uncovered with this method, such as broadband negative dynamic mass, are reexamined. In tandem, a bending wave excitation arrangement and characterization method is introduced. Low bending and quasi-longitudinal phase speeds in addition to high static and low dynamic moduli shed light on the enhanced noise and vibration control performance reported in the literature. This paper discusses the dynamic measurement method and possible applications which may benefit from this unique combination of properties.