An electrical machine includes a stator assembly having an annular core and a conductive winding. The annular core includes a central bore. The conductive winding includes one or more stator winding bars disposed circumferentially around the central bore. The one or more stator winding bars include a core conductor and an insulation layer surrounding the core conductor. An end segment of the one or more stator winding bars at a connection interface includes a stress control structure surrounding the insulation layer. The stress control structure includes a printed scaffold and a dielectric backfill material. The dielectric backfill material fills pores of the printed scaffold. The porous scaffold is composed of a stress control material that is different from the dielectric backfill material.