Pyrotechnic protections against fragments: experimental and numerical method results

As part of its activities, CEA carries out experiments on pyrotechnic devices. For some of them, the detonation process generates a sheaf of fragments which could damage measuring equipment (sensors, highspeed, cameras, X-ray detectors…). Thus, the design of fragments mitigation protection is a significant part of the experimental set-up definition. Furthermore, the choice of these protections is driven by safety requirements and by various constraints related to the performances of the measuring equipment needed for the experimentation (for example, high quality radiographic images can only be achieved by minimizing the mass of materials located in the line of sight).



Experimental and numerical studies are thus carried out at CEA to identify and qualify the most suitable protection system, considering the constraints to obtain the best compromise between safety and measurements. This protection system consists of a glass plate first as well as a stack of different materials including ceramic, composite and polymer materials with metal backing. This study focuses on the protection’s second stack.



More than forty ballistic tests were carried out on these materials and demonstrate their mitigation efficiency.

Numerical simulations of these experiments were then performed with a Finite Element (FE) method of LS-DYNA code. The aim is to be able to build the most accurate calculation protocol, and especially for the complex behavior of ceramics and polymers at high strain rates.



Their efficiency is assessed in terms of fragments velocity drop after passing through various protection system. The comparison between the experimental data and the simulations approach shows that the FE numerical tool is, in most cases, in good agreement with experiences.