Blast shock wave mitigation using the hydraulic energy redirection and release technology

Abstract

A hydraulic energy redirection and release technology has been developed for mitigating the effects of blast shock waves on protected objects. The technology employs a liquid-filled plastic tubing as a blast overpressure transformer to transfer kinetic energy of blast shock waves into hydraulic energy in the plastic tubings. The hydraulic energy is redirected through the plastic tubings to the openings at the lower ends, and then is quickly released with the liquid flowing out through the openings. The samples of the specifically designed body armor in which the liquid-filled plastic tubings were installed vertically as the outer layer of the body armor were tested. The blast test results demonstrated that blast overpressure behind the body armor samples was remarkably reduced by 97% in 0.2 msec after the liquid flowed out of its appropriate volume through the openings. The results also suggested that a volumetric liquid surge might be created when kinetic energy of blast shock wave was transferred into hydraulic energy to cause a rapid physical movement or displacement of the liquid. The volumetric liquid surge has a strong destructive power, and can cause a noncontact, remote injury in humans (such as blast-induced traumatic brain injury and post-traumatic stress disorder) if it is created in cardiovascular system. The hydraulic energy redirection and release technology can successfully mitigate blast shock waves from the outer surface of the body armor. It should be further explored as an innovative approach to effectively protect against blast threats to civilian and military personnel.

Figure 1. The structure of specifically designed body armor sample and its potential mechanism for blast shock wave mitigation.

(a) A photograph showing the sample of the body armor that includes the water-filled plastic tubings, end caps, Kevlar panel, and heat resistant cloth fabrics; (b) A schematic diagram illustrating a side view of the sample of the body armor after a blast shock wave impacts the sample. The rapid compression effects of blast shock wave on the sample create an action force to compress water-filled plastic tubing and make it move against the Kevlar panel. Because the Kevlar panel is a hard plate fixed on a test frame, it will exert a reaction force against the plastic tubing. The action and reaction forces push water moving towards the lower end of the plastic tubing. Since water is incompressible, increased liquid pressure on the lower end forces the end cap to open and make water to spray out through the opening from the tubin, thus rapidly decreasing the liquid pressure inside of the tube.

Figure 2. Experimental setup and the blast-testing equipments.

(a) A photograph of the blast-testing equipment including shock tube, test frame, and front and sensors for assessment of the protective effects of the specially designed blast-resistant body armor against blast overpressure waves; (b) Schematic diagram of the blast-testing equipments. The sample of the body armor is fixed on a test frame that was approximately 40 cm away from the shock tube opening. The front sensor is placed 2 cm before the sample and the rear sensor is placed 4 cm behind the sample.

Figure 3. Actual pressure-time histories for both the front sensor and rear sensor during the first 0.4 msec after blast.

The peak pressure of blast wave significantly decreases from 10.14 psi (pressure before plastic tubings) measured by the front sensor to 0.27 psi (pressure behind plastic tubings) measured by the rear sensor.

Figure 4. The peak pressures without protection material and behind different types of protection materials, measured using the rear sensor.

The peak pressure measured without protection material was 8.25±0.48 psi (n = 4). The peak pressures behind Kevlar panel, plastic tubing layer and a combination of plastic tubing layer and Kevlar panel were 5.33±0.33 (n = 3), 0.27±0.02 (n = 5) and 0.25±0.004 psi (n = 4), respectively.

Figure 5. The potential mechanism by which the blast shock wave causes noncontact, remote damage to the underwater objects (such as ships, underwater animals and humans) through water, and to the human organs or tissues through blood.