The layering of foam-based elastomeric materials with more rigid materials appears to increase energy dissipation, potentially mitigating damage from blast overpressure when used in conjunction with ballistic protective equipment. This work studies the attenuation of blast load through the thoracic protection layers of a representative bomb suit under realistic loading conditions. It is known that hysteresis loss in unloading can significantly affect energy attenuation. Varying the relative density, a critical foam parameter, also shows interesting blast attenuation results; an increase in relative density increases the quasi-static stress state during the plateau stage of deformation but reduces the densification strain. The effect of relative density appears associated with impedance match/mismatch that allows for absorption of energy into the foam and its dissipation, assuming that full compaction is avoided. Modeling results using LS-DYNA to analyze blast wave attenuation across the layup are presented.

The other components in the protective equipment also play a role in overpressure attenuation. The effect of soft armor, and solid polymer layers in the layup are included with suitable physics-based models. The influence of the material composition of the rigid front plate is examined. The rigid front plate is a critical component of the protective layup as its mass controls the balance of incoming blast energy with the transferred kinetic and internal energy in the layup. Conversely, the impedance mismatch between the front metal and the foam based layups may reduce the wave energy transmission. The interaction of these two effects leads to complex features in the model and creates a challenging design problem.

To optimize blast attenuation, according to several intuitively selected metrics, such as peak stress and total impulse transmission, the effect of various physical foam properties as well as lamination thickness and order of material layers are shown. The modeling effort includes a parametric analysis of the foam relative density, its mechanical response, and cell structure, etc. Realistic and physical material models for elastomeric foams were considered and evaluated.. The performance of certain alternative foam candidates was studied against near field and far field blast loading conditions. Multiple foam layups were incorporated to study the combined performance of strategically placed low density and high density foams for overall optimum blast attenuation. It is hypothesized that layers with different densities and properties can compensate for the deficiencies observed in the individual performance when used together in different combinations. The selection of such layups must be done in terms of plateau stress and densification region. As an example it was observed that, in certain cases, higher plateau stress foams should be placed in front of lower plateau stress foams for best response. These modeling and physical conclusions are expected to provide rules and tools for design of the foam material and geometrical properties as well as potential layup modifications.


Blast Wave Attenuation Across Foam-Based Protective Composite Layups

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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