Experimental investigation of the interaction of shock waves with textiles

Abstract

Experimental studies have been performed to investigate the pressure amplification experienced behind a textile when exposed to a shock wave. Three textiles with different masses and air permeabilities were studied. Mach numbers for tests varied between 1.23 and 1.55. The distance between the back wall and the textile was varied between 3 and 15 mm. It was found that in most cases the presence of the textile led to a pressure amplification at the back wall. This amplification was dependent on the textile, Mach number and distance from the back wall. The processes causing the pressure amplification were identified by analysing pressure traces and contact shadowgraphs. It was found that when the incident wave impinges on the textile, a part is reflected upstream and a part is transmitted through the textile. The transmitted portion reflects back and forth in the gap between the textile and the back wall leading to a back wall pressure trace with a stepped profile. In addition, the textile moves towards the back wall causing compression waves to propagate towards the back wall. The combination of the stepped profile and the compression waves cause the pressure amplification. The contribution of each mechanism depends on the textile properties. Approximate wave diagrams have been constructed. Tests involving multiple layers of textiles are also discussed.

Blast Pressure Amplification due to Textile Coverings

“…Shock tube studies [6] support the field observations. These studies focus on the actual mechanisms that lead to the pressure amplification, which is defined as the ratio of peak pressure on the surface with textile present, to that which would be achieved with shock reflection off a bare surface.…”

“…For the visualization tests and those with gelatin backing the same textiles were used as in the previous study [6], namely satin, polycotton, and muslin, as shown in Figure 3, and having the properties listed in Table 1. The samples shown were 76 mm wide and the insert, at five times magnification, gives an indication of the structure.…”

“…Figure 2 Wall pressure due to shock wave reflection. For single and multi-layer pressure tests a random selection of other textile materials were used, since amplification tests have already been reported for the textiles listed in Table 1 [6]. These new samples were arbitrarily chosen to represent as wide a range as could be found.…”

“…When a backing plate is present the transmitted wave is reflected from it and this reflected wave returns to the textile surface where a new set of transmitted and reflected waves occur as discussed in [6].…”

A simple constitutive model for predicting the pressure histories developed behind rigid porous media impinged by shock waves

“…When supported by a rigid wall, the overall stress acting on the wall can be reduced or amplified depending on whether the porous medium is rigid or flexible, respectively. Stress amplification has been reported in experiments with flexible porous materials such as polyurethane foams (Skews 1991;Baer 1992;Levi-Hevroni et al 2002;Seitz & Skews 2006), textiles (Hattingh & Skews 2001) and granular materials when theywere placed immediately adjacent to a supporting wall (Ben-Dor et al 1997; † Email address for correspondence: sorens@bgu.ac.il 508 O. Ram and O. Sadot Britan et al 1997b;.…”