This study investigates the response of flexible piezoelectric materials exposed to blast wave pressure impulses from inair and underwater explosions. A shock tube was used to produce reproducible shock waves from explosions with average peak pressures in excess of 1,000 kPa for underwater experiments and 100 kPa for in-air experiments. Flexible piezoelectric polyvinylidene fluoride (PVDF) and lead zirconate titanate Pb(Zr,Ti)O3 (PZT) materials were tested for sensing the pressure impulse generated from an explosion. The rise time, peak amplitude, and duration of the blast wave pressure impulse were measured for each piezoelectric material and compared to an OEM blast wave sensor. This study uniquely identifies flexible piezoelectric materials that can accurately measure the blast wave pressure impulse from both in-air and underwater explosions. The accurate response and flexibility of the selected piezoelectric materials demonstrate the potential to be integrated into several forms of sensors, including wearable. Military and industrial applications can potentially benefit from a wearable blast wave sensor to improve medical diagnosis and treatment of blast exposure.
A controllable damper that utilizes a friction type magnetorheological gel (MRG) valve and liquid spring technology was designed, built, and characterized under this study. A high-performance MRG material was developed for this damper, where the design space constraints minimized the damper dimensions. Electromagnetic finite element analyses were performed to optimize the controllable and liquid spring valve dimensions. The liquid spring valve utilized shim stacks for asymmetric rebound and compression loading. System modeling was performed where the effectiveness of various control system algorithms in reducing the transmitted acceleration levels were analyzed. The fabricated liquid spring controllable damper was characterized, and then installed on a single degree-of-freedom quarter-car experimental system. The characterization study demonstrated the liquid spring effect, as well as the controllability of the device. The quarter car experiments revealed that the device is more effective in reducing the acceleration levels at relatively higher operating speeds (up to 11 in/s). The device was also tested for spring stiffness at elevated temperatures. It was demonstrated that the liquid spring stiffness changes minimally at high operating temperatures.