A power coupler for transferring rotary power from a rotary power device to a load device includes a shear thickening fluid (STF) and a chamber that contains the STF. The power coupler further includes a drive shaft housed radially within a drive side section of the chamber and protruding outward from an end of the chamber for coupling to the rotary power device. The power coupler further includes a load shaft housed radially within a load side section of the chamber and protruding outward from another end of the chamber for coupling to the load device. The power coupler further includes a drive turbine housed radially within the drive side section and coupled to the drive shaft. The power coupler further includes a load turbine housed radially within the load side section at a fixed operational distance from the drive turbine and coupled to the load shaft.