S2 and in previous studies. The RVEs were created and meshed in Gmsh version 4.7.0. First order tetrahedral meshes were used, and they were optimized using the Netgen extension. Meshes were further refined on the surfaces of the inclusions, based on local curvature and until suitable convergence was obtained, as described in Sec. S3. Finite element calculations were performed using the GetDP solver, version 3.3.1.