In many parts of the world, civilians and peacekeepers are exposed to potentially serious injury from blasts and explosions. Providing insight into the trauma thresholds for blast injury is necessary for the development of blast protection equipment and identification and subsequent treatment of blast injury. [Phillips, 1988] Blast injury can be categorized as primary, secondary, tertiary, quaternary and quinernary, corresponding to different aspects of the blast loading and injury mechanisms. Primary blast injury occurring in the lungs is of importance, since lung injury results in one of the highest rate of blast mortality. Much of the existing blast injury data was obtained from animal testing with sheep and subsequently extrapolated to humans using scaling techniques. More recently, mathematical, experimental and numerical models have been developed and employed to investigate blast injury. In this study, a detailed finite element model of a sheep thorax and human thorax (developed at the University of Waterloo) was used to predict primary blast lung injury based on a range of blast loading conditions. The models were developed based on available anatomical data and material properties to model the organs and tissues, and were evaluated using the LS-Dyna explicit finite element code. The models were previously validated for the prediction of lung PBI using Friedlander-type blast waves. All results were compared to existing literature to further verify and validate the numerical models as wells as to provide insight on the effect of loading conditions on blast injury. The blast loading input for these simulations used idealized blast waves, based on a blast physics approach. Blast loads were verified using the Chinook CFD software. The effects of idealized blast waves on predicted lung injury were investigated to determine the importance of peak pressure, blast wave duration and impulse. The duration and peak pressures for the waves were selected based on the Bowen and UVa curves, and included a right angle triangular shape and a square wave to allow for the different parameters to be considered. These results were compared to the Bowen and revised Bowen injury models. The results show that the peak overpressure is dominant in predicting injury for blast loads with long durations (>8 ms). The impulse was dominant in predicting injury for blast loads with short durations (<1 ms). For blasts loads with intermediate durations (1 ms < 8 ms) both the shape of the blast load wave and peak overpressure play a role in primary blast lung injury. The effect of orientation of the body position on primary blast lung injury was investigated. Simulations were performed using the sheep and human numerical models along with a model of a commonly used experimental device, the Blast Test Device (BTD) cylinder. These models were oriented in different positions by rotating the body relative to the blast flow. Injury results for the BTD were calculated using the Injury 8.1 injury prediction software. The BTD simulations served several purposes; it was used as a reference for the human and sheep simulations and its effectiveness as a tool to predict body orientation was evaluated. In general, all of the models predicted appropriate and similar levels of injury for the body in its default orientation, and these predictions were comparable to the accepted injury levels for this insult. For other orientations the BTD was not able to predict the appropriate blast injury. This highlighted the importance of proper placement and orientation of the BTD when used in simulations or physical experiments. The overall injury (based on the results from the right and left lung) predicted by the sheep and human thorax was similar for all orientations. However, very different results were obtained when the predicted injury for the right and left lungs was compared. The differences between the sheep and the human were examined and the differences in injury between the right and left lung is a result of the differences in anatomy between the two species. This study has evaluated the importance of blast wave parameters in predicting primary blast injury, an important consideration for the improvement of blast protection, and the effect of body orientation on primary blast injury, an important consideration for experimental testing and a starting point for the evaluation of complex blast loading. Future work will focus on the evaluation of injury in complex blast environments.

In many parts of the world, civilians and peacekeepers are exposed to potentially serious injury from blasts and explosions. Providing insight into the trauma thresholds for blast injury is necessary for the development of blast protection equipment and identification and subsequent treatment of blast injury. [Phillips, 1988] Blast injury can be categorized as primary, secondary, tertiary, quaternary and quinernary, corresponding to different aspects of the blast loading and injury mechanisms. Primary blast injury occurring in the lungs is of importance, since lung injury results in one of the highest rate of blast mortality. Much of the existing blast injury data was obtained from animal testing with sheep and subsequently extrapolated to humans using scaling techniques. More recently, mathematical, experimental and numerical models have been developed and employed to investigate blast injury. In this study, a detailed finite element model of a sheep thorax and human thorax (developed at the University of Waterloo) was used to predict primary blast lung injury based on a range of blast loading conditions. The models were developed based on available anatomical data and material properties to model the organs and tissues, and were evaluated using the LS-Dyna explicit finite element code. The models were previously validated for the prediction of lung PBI using Friedlander-type blast waves. All results were compared to existing literature to further verify and validate the numerical models as wells as to provide insight on the effect of loading conditions on blast injury. The blast loading input for these simulations used idealized blast waves, based on a blast physics approach. Blast loads were verified using the Chinook CFD software. The effects of idealized blast waves on predicted lung injury were investigated to determine the importance of peak pressure, blast wave duration and impulse. The duration and peak pressures for the waves were selected based on the Bowen and UVa curves, and included a right angle triangular shape and a square wave to allow for the different parameters to be considered. These results were compared to the Bowen and revised Bowen injury models. The results show that the peak overpressure is dominant in predicting injury for blast loads with long durations (>8 ms). The impulse was dominant in predicting injury for blast loads with short durations (<1 ms). For blasts loads with intermediate durations (1 ms < 8 ms) both the shape of the blast load wave and peak overpressure play a role in primary blast lung injury. The effect of orientation of the body position on primary blast lung injury was investigated. Simulations were performed using the sheep and human numerical models along with a model of a commonly used experimental device, the Blast Test Device (BTD) cylinder. These models were oriented in different positions by rotating the body relative to the blast flow. Injury results for the BTD were calculated using the Injury 8.1 injury prediction software. The BTD simulations served several purposes; it was used as a reference for the human and sheep simulations and its effectiveness as a tool to predict body orientation was evaluated. In general, all of the models predicted appropriate and similar levels of injury for the body in its default orientation, and these predictions were comparable to the accepted injury levels for this insult. For other orientations the BTD was not able to predict the appropriate blast injury. This highlighted the importance of proper placement and orientation of the BTD when used in simulations or physical experiments. The overall injury (based on the results from the right and left lung) predicted by the sheep and human thorax was similar for all orientations. However, very different results were obtained when the predicted injury for the right and left lungs was compared. The differences between the sheep and the human were examined and the differences in injury between the right and left lung is a result of the differences in anatomy between the two species. This study has evaluated the importance of blast wave parameters in predicting primary blast injury, an important consideration for the improvement of blast protection, and the effect of body orientation on primary blast injury, an important consideration for experimental testing and a starting point for the evaluation of complex blast loading. Future work will focus on the evaluation of injury in complex blast environments.

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.

Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study. Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury. Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate). The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.