Mechanical behavior of the PEGASUS railgun projectile during the launch

The PEGASUS facility houses one of the railguns of the French-German Research Institute of Saint-Louis (ISL). With its 10 MJ distributed energy storage and a 6 m long launcher tube, projectiles with a mass of several hundred grams are accelerated to muzzle velocities greater than 2000 m/s. The fiber brush armatures are supported by a sabot made of glass-fiber-reinforced plastic (GFRP), an orthotropic insulating material with the best mechanical performance found so far. If the muzzle velocity is intended to be substantially increased, the sabot material may reach its mechanical limits due to the high dynamic loading. Hence a precise understanding of the material behavior will be necessary, especially with regard to the failure mechanisms that occur. The mechanical behavior of the sabot is analyzed by means of numerical simulation combining two 3D-finite-element codes: the electromagnetic code MEGA and the mechanical dynamic code LS-DYNA3D. The Lorentz force computed by MEGA is introduced into LS-DYNA3D as a time- and space-dependent volumetric load inside the brushes. By calculating the stress-strain distribution of the sabot, the regions, which are liable to fail, can be identified. The simulation results are validated by comparison with the experimental work using the X-ray photographs taken at the muzzle of the launcher.