Non-singular black holes and mass inflation in modified gravity

We analytically derive a class of non-singular, static and spherically symmetric topological black hole metrics in F(R)-gravity. These have not a de Sitter core at their centre, as most model in standard General Relativity. We study the geometric properties and the motion of test particles around these objects. Since they have two horizons, the inner being of Cauchy type, we focus on the problem of mass inflation and show that it occurs except when some extremal conditions are met.