Flex coupler for hybrid gas turbine engine powerplant

An engine system, comprising:

• a gas turbine engine including an engine rotating structure, a compressor section, a combustor section, a turbine section and a flowpath extending through the compressor section, the combustor section and the turbine section, the engine rotating structure comprising a turbine rotor within the turbine section;
• an electric machine comprising an electric machine rotating structure;
• and
• a flex coupler rotatably connecting the electric machine rotating structure to the engine rotating structure, the flex coupler including
• a first mount including a plurality of first mount fingers arranged circumferentially about an axis;
• a second mount including a plurality of second mount fingers arranged circumferentially about the axis;
• and
• a flex plate connecting the first mount to the second mount, the flex plate including a plurality of first flex plate fingers and a plurality of second flex plate fingers, each of the plurality of first flex plate fingers attached to a respective one of the plurality of first mount fingers, and each of the plurality of second flex plate fingers attached to a respective one of the plurality of second mount fingers.