Experimental Studies on Mitigating the Risk of Air Blast Loading

Abstract

Blast loading events that arise from the detonation of explosives pose a severe threat to the lives of civilians and military personnel alike. Such dangers typical of a detonation event include but are not limited to an intense, sudden initial pressure spike, extreme temperatures due to the burning of gases released by the explosive, and damage to the integrity of surrounding structures. It is therefore the purpose of the studies detailed in this manuscript to investigate various methods of mitigating the dangers posed by shock loading, as well as to investigate a novel impact mitigation device. To address the danger presented by high velocity glass fragments generated by windows that have failed due to shock loading, a study was conducted to evaluate the effectiveness of coated laminated safety glass panels’ ability to contain glass fragments when subject to shock loading over a range of temperature conditions. Using a shock tube apparatus, fully clamped specimens were loaded under room temperature (25 °C), low temperatures (-10 and 0 °C), and high temperatures (50, 80, 110 °C). For each experiment, the incident and reflected shock wave pressure profiles were recorded and three-dimensional Digital Image Correlation was used to analyze high-speed images and compute the full-field deformation, in-plane strains, and velocities during the blast-loading event. A post-mortem study of the sandwich specimen was performed to investigate the effectiveness of such materials under different temperatures to withstand these shock loads. The composite panel showed great endurance during the blast loading for temperatures from 0 to 80 °C, however was unable to contain glass fragments at -10 °C and 110 °C. A new system was designed to mitigate the impact forces during a collision using shock loading. The device consists of a cylindrical composite bladder sealed on one end by an inflation valve and on the other by an aluminum sheet of variable thickness. The bladder is pressurized and as an impactor nears the device, it strikes a striker-needle which ruptures the aluminum sheet, thus producing a shockwave just prior to impact. This produced shock wave decelerates the impactor and creates momentum (impulse) opposing that impulse transmitted from the impactor. Drop weight experiments were performed to show the applicability of this anti-shock device in reducing the momentum of the incoming body. A range of variables including needle length, bladder pressure, impact velocity, and drop mass were tested to better understand the processes involved. Time lapse photography