Composite hydrophone devices coupling piezoelectricity and tensegrity

The concept of tensegrity as conceived by Buckminster Fuller has been incor porated into a passive hydrophone device. Tensegrity is described as the ph ysical phenomenon that produces a stable geometric structure using solid co mpressional elements arranged in tandem with Flexible tensional cables. In the devices built by the authors, six PZT 5H(TM) bars acting as compression al elements in the tensegrity structure have been coupled with tensional ba nds of either polyaramid or carbon fiber. This stable system is then wrappe d with an outer layer of either polyaramid or carbon fiber and rubber film to form a sealed device, which is referred to as a piezotensegritive device in this paper. The six bars are arranged in parallel electrical connectivi ty for all devices described. The resonant frequency for these devices rang ed from 19.5 to 20.3 kHz depending on the material used for wrapping the pi ezoelectric bars. These devices were also tested in a hydrostatic environme nt to determine the relevant piezoelectric coefficients. For devices wrappe d with carbon fiber, d(h) peaked at similar to 6000 pC/N and g(h) at simila r to 275 mVm/N. For devices wrapped with polyaramid, d(h) peaked at similar to 2000 pC/N and g(h) at similar to 100 mVm/N. Sensitivities from -182-195 db ref. 1 V/mu Pa were calculated for these devices.