Dynamic calibration and implementation of PVDF gauges for shockwave measurements

Abstract. Measurement of shock waves characteristics like overpressure or impulse require specifics pressure sensors and acquisition devices. Piezoceramics sensors are commonely used in this way. Nevertheless, there cost and intriseque conditionning integration may not suitable with near fields applications. Piezoelectrics polymers like PVDF pressure gauges may be an alternative due to there cheep cost and manufacturing process but they need to be precisely conditionned (electrically and mechanically). In this context, we propose a methodology to calibrate these PVDF pressure sensors. The first part of the study presents various steps to build the PVDF pressure sensor, the conditonning electrical circuit, the insulation process and the mechanical integration. Then, we performed experiments on the shocktube facility at ENSTA Bretagne. This facility can generates two types of pressure sollicitations, relative to the length of the driver section : The shock configuration, with a pressure plateau, and a more realistic configuration, the blast (or Friedlander like) configuration. The intensity of the overpressure is ruled by the thickness of mylar sheets placed between the driver section and the test section. Six piezoelectrics sensors (PCB piezoelectronics) along the test section measure the incident pressure and one at the back, measuring the reflected wave. The uniformity of the shockwave is observed with shadowgraph technique recorded on a high-speed camera. All these informations coupled with analytical model of shocktube characteristics ensure the validity of the set-up. Finally, the signal of the reflected sensor is compared with the PVDF sensor signal. The analysis of the signals exhibit the dynamic response of the PVDF sensor, the characterization of the electrical noise due to the prior conditionning and the suitability of the methodology to measure reflected blastwaves