I am doing a low velocity impact with sandwich structures which face is Carbon/epoxy T300/QY8911 and core is Nomex honeycomb. I use the mixed approach to model sandwich structures by defines shells for top and bottom layer and solid for middle layer.

But after I run the simulation, the results is quite weird , there are some warnings about the initial penetration in contact id 3 which use contact type 25 to define and I cannot solve it.
The stress contour of this simulation, the stress did not happen in the core layer and I do not know why. The gray area of core layer means no results but I really do not know how to solve it. I think it's about the modelling of sandwich structure but I have no idea how to do. Please help me.
I will attach the model file in case of you would like to check my set up.
Thank you in advance.
Paphatsorn

