Golf club head or other ball striking device with thermoreactive face

A golf club head comprising:

• a face having a ball striking surface and an inner surface opposite the ball striking surface;
• a body connected to the face and extending rearward from the face, the body and the face defining a cavity behind the face;
• a thermally-active device contacting the inner surface of the face and positioned in the cavity, wherein the thermally-active device is configured to change a temperature of a portion of the face to change a modulus of the portion of the face;
• and
• a power source positioned within the cavity and in communication with the thermally-active device, wherein the power source is configured to supply power to the thermally-active device to change the temperature of the portion of the face.

A golf club head comprising:

• a face having a ball striking surface and an inner surface opposite the ball striking surface;
• a body connected to the face and extending rearward from the face;
• and
• a thermally-active device connected to the face, wherein the thermally-active device is configured to change a temperature of a portion of the face to change a modulus of the portion of the face.

A golf club head comprising:

• a face having a ball striking surface and an inner surface opposite the ball striking surface;
• a body connected to the face and extending rearward from the face, the body and the face defining a cavity behind the face;
• a thermally-active device contacting the inner surface of the face and positioned in the cavity, wherein the thermally-active device is configured to change a temperature of a portion of the face to change a modulus of the portion of the face;
• and
• an actuator in communication with the thermally-active device, the actuator configured to be controllable by a user to activate the thermally-active device to change the temperature of the portion of the face.

A wood-type golf club head comprising:

• a face having a ball striking surface and an inner surface opposite the ball striking surface, the face having an area of highest response, wherein at least a portion of the face located around the area of highest response is formed of a material that has a first molecular phase at ambient conditions and a second molecular phase at a different temperature, wherein the material has a different modulus in the second molecular phase compared to the first molecular phase;
• a body connected to the face and extending rearward from the face, the body having a crown, a sole, a heel, and a toe, wherein the body and the face define an enclosed internal cavity behind the face;
• a thermally-active device positioned within the cavity and connected to the inner surface of the face proximate the area of highest response, wherein the thermally-active device is configured to change a temperature of the portion of the face located around the area of highest response, and wherein the thermally active device is configured to generate a temperature change sufficient to cause the material to change to the second molecular phase;
• and
• a power source positioned within the cavity and connected to an upper surface of the sole, wherein the power source is in communication with the thermally-active device and is configured to supply power to the thermally-active device to change the temperature of the portion of the face.