The mitigation of primary blast injury
File(s)
Author(s)
Magnus, Danyal
Type
Thesis
Abstract
While effective against penetrating threats, ballistic armour may not mitigate primary blast injuries inflicted by the pressure wave. It remains poorly understood whether such armour improves blast clinical outcome for the wearer. The aim of this work was to deepen understanding of the nature of modern primary blast injuries, potential materials appropriate for personal blast protection and the influence of hard ballistic plates on expected survivability.
The modern prevalence and severity of blast in the civilian environment was investigated by carrying out a meta-analysis of injured populations. The occurrence of primary blast injuries strongly depends on the ventilation of the attack environment. As the rate of pulmonary injury for Improvised Explosive Device attacks is approximately 9%, it is apparent that the blast attenuating capability of thoracic armour is of importance.
The blast mitigation performance of polyurethane-based foams, hydrogels and a hard ballistic plate were assessed using a shock tube. The foams and hydrogels were manufactured and mechanically characterised across strain rates from 0.01–1600/s covering regimes relevant to both load-bearing and blast loading scenarios. While reticulated polyurethane foam enhanced the peak blast pressure, the hydrogels dissipated blast energy through brittle fracture. A ballistic gelatine human thorax surrogate was used to evaluate the clinical significance of the mitigation, and the blast loading of the gelatine computationally modelled. The hydrogels yielded a 90% reduction of peak pressure compared to the unarmoured case, comparable to values reported for water-based mitigation systems. By comparison, the addition of a ballistic plate with zero air gap increased lethality from values up to 50% in the unarmoured case to values up to 99%. Under the highest amplitude and duration blast loading, this corresponded to an increase of the delivered peak pressure and impulse to the surrogate of 52% and 27%, respectively, compared to the unarmoured case. Introduction of an air gap between the surrogate and armour further increased the lethality risk to near 99% over the full range of loading conditions due to blunt impact of the plate. However, mitigation could be achieved by combining the ballistic plate with a reticulated foam backing layer greater than a critical thickness.
The modern prevalence and severity of blast in the civilian environment was investigated by carrying out a meta-analysis of injured populations. The occurrence of primary blast injuries strongly depends on the ventilation of the attack environment. As the rate of pulmonary injury for Improvised Explosive Device attacks is approximately 9%, it is apparent that the blast attenuating capability of thoracic armour is of importance.
The blast mitigation performance of polyurethane-based foams, hydrogels and a hard ballistic plate were assessed using a shock tube. The foams and hydrogels were manufactured and mechanically characterised across strain rates from 0.01–1600/s covering regimes relevant to both load-bearing and blast loading scenarios. While reticulated polyurethane foam enhanced the peak blast pressure, the hydrogels dissipated blast energy through brittle fracture. A ballistic gelatine human thorax surrogate was used to evaluate the clinical significance of the mitigation, and the blast loading of the gelatine computationally modelled. The hydrogels yielded a 90% reduction of peak pressure compared to the unarmoured case, comparable to values reported for water-based mitigation systems. By comparison, the addition of a ballistic plate with zero air gap increased lethality from values up to 50% in the unarmoured case to values up to 99%. Under the highest amplitude and duration blast loading, this corresponded to an increase of the delivered peak pressure and impulse to the surrogate of 52% and 27%, respectively, compared to the unarmoured case. Introduction of an air gap between the surrogate and armour further increased the lethality risk to near 99% over the full range of loading conditions due to blunt impact of the plate. However, mitigation could be achieved by combining the ballistic plate with a reticulated foam backing layer greater than a critical thickness.
Version
Open Access
Date Issued
2020-01
Date Awarded
2020-06
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Proud, William
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)