Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMIBiomechanical analyses for personal Protection technologies and body protection
Injuries caused by deformation of protective equipment
Behind Armor Blunt Trauma (BABT) is caused by non-penetrating ballistic impacts caused by the rapid deformation of personal protective equipment (PPE). During the impact, the PPE and the underlying body tissue deform rapidly. This highly dynamic load can cause bruises, tears, fractures and injuries to organs. A measurement of the maximum deformation depth in ballistic sound (“back-face deformation”, BFD – limit value of 44 mm first defined in 1979 by the US Department of Justice) is still used almost worldwide today for the certification of protective vests. However, there is no direct causal relationship between BFD and the severity of the resulting injuries in humans. Numerical human body models (“HBM”) can now be used to question these ballistic limits and to investigate this special form of ballistic load depending on the body region. Fraunhofer EMI is pursuing the goal of developing virtual calculation methods with a high level of predictive capability in order to be able to analyze issues relating to impact-like load effects on the body when using personal protective technologies. This will expand the assessment capability for PPE and body protection.
Experimental analysis of load effects
A high level of predictive reliability of numerical calculations is supported by experimental validation. Suitable surrogate materials are required for this. The targeted development of surrogate bone materials for ballistic dummies is currently part of a dissertation at EMI entitled “Simulation methods for the predictive analysis of bone surrogates”. Conventional crash test dummies from the automotive industry are to be further developed and used for military or police purposes. This means that the effectiveness of personal protective equipment can be investigated experimentally at Fraunhofer EMI when worn with the aid of dummies. The use of numerical human models also enables the quantitative assessment of injury risks and thus a better design of PPE products, which is associated with greater protection against injuries. An additional modeling method was developed for this purpose in order to convert simple textile elements from a 2D form into a 3D form that adapts to the virtual body surface. This technique is generally a simple means of draping flexible objects over three-dimensional contours.
