Composite hydrophone devices coupling piezoelectricity and tensegrity

The concept of tensegrity as conceived by Buckminster Fuller has been incorporated into a passive hydrophone device. Tensegrity is described as the physical phenomenon that produces a stable geometric structure using solid compressional elements arranged in tandem with flexible tensional cables. In the devices built by the authors, six PZT 5H™ bars acting as compressional elements in the tensegrity structure have been coupled with tensional bands of either polyaramid or carbon fiber. This stable system is then wrapped 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 connectivity for all devices described. The resonant frequency for these devices ranged from 19.5 to 20.3 kHz depending on the material used for wrapping the piezoelectric bars. These devices were also tested in a hydrostatic environment to determine the relevant piezoelectric coefficients. For devices wrapped with carbon fiber, d_h peaked at ∼6000 pC/N and g_h at ∼275 mVm/N. For devices wrapped with polyaramid, d_h peaked at ∼2000pC/N and g_h at ∼100mVm/N. Sensitivities from –182–195 db ref. 1V/μPa were calculated for these devices. Received: 7 September 1999 / Reviewed and accepted: 15 September 1999