Maximum stress in uniaxial compression

fsaizpoy

Hello,
I have a question. What is the maximum stress that a Si body can experience when it is loaded in a uniaxial compression with another solid body at a few km/s? Is it the stagnation pressure of the impacting body (0.5*density*piston_velocity^2) or is the maximum pressure given by the conservation of momentum of shock waves (density_ahead_shock*piston_velocity*shock_velocity) ?

Thanks,
- Fernan