Question on modeling geometry in ABAQUS CAE

Hello all,



I am modeling a composite cube block with spherical particle and spherical interphase around particle. I can simplify two spheres to two cubes. I am trying to model particle inclusion and interphase in a composite material. I am taking matrix as a cube and particle as a small cube at the center of matrix cube. Interphase layer will be another cube at the center of matrix cube but bit bigger than particle cube. Matrix, interphase, matrix all have different properties. But problem is I do not know how to model a cube inside a cube.

When I assembled three parts, they can get 'separated' during simulation. I cannot model all 3 cubes as a single part. If I do boolean, the innermost geometry gets deleted. Importantly, I also want to make different sets for different parts.



Any suggestions on how to model this?