Disclosed herein are example variable flowpath casings for blade tip clearance control. An example casing for a turbine engine includes an annular substrate extending along an axial direction, the annular substrate defining a cavity at a radially inward surface of the annular substrate, and a smart structure coupled to the annular substrate, the smart structure including a support structure; an actuator structure to at least one of expand or contract in response to a change in temperature of the actuator structure, and a variable surface coupled to the support structure, the support structure to move the variable surface in a radial direction.