Golf club head or other ball striking device with thermoreactive face

1. A 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 located proximate a center of the ball striking surface, wherein the face is formed of a first material and further comprises an insert forming at least a portion of the area of highest response, the insert being formed of a second material having a thermal modulus response that is different from a thermal modulus response of the first material, wherein the thermal modulus response of the second material is configured such that heat generated by an impact of a golf ball striking surface of at least 90 ft/s is sufficient to reduce a modulus of the second material by at least 10% relative to the modulus of the second material at ambient conditions; and

a body connected to the face and extending rearward from the face.

2. The golf club head of claim 1 , wherein the insert is located behind the ball striking surface, such that an entirety of the ball striking surface is formed of the first material.

3. The golf club head of claim 1 , wherein the insert is located within a recess on the inner surface, such that an entirety of the ball striking surface is formed of the first material.

4. The golf club head of claim 1 , wherein the insert forms at least a portion of the ball striking surface.

5. The golf club head of claim 1 , wherein the modulus of the second material at ambient conditions is within 5% of a modulus of the first material at ambient conditions, and wherein heat generated by an impact of a golf ball on the ball striking surface of at least 90 ft/s is sufficient to reduce the modulus of the second material to at least 20% lower than the modulus of the first material, due to the different thermal responses of the first and second materials.

6. A golf club comprising the golf club head of claim 1 and a shaft connected to the head.

7. 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 located proximate a center of the ball striking surface, wherein at least a portion of the area of highest response is formed of a material with a thermally-variable modulus such that the material has a first modulus due to heat generated by an impact of a golf ball on the ball striking surface at about 90 to 130 ft/s and a second modulus due to heat generated by an impact of the golf ball on the ball striking surface at about 160 ft/s, the second modulus being no more than 5% different from the first modulus, and wherein the material has a third modulus at ambient conditions, the third modulus being at least 20% greater than the first modulus; and

a wood-type body connected to the face and extending rearward from the face, the body and the face defining an internal cavity behind the face.

8. The wood-type golf club head of claim 7 , wherein the material forming the at least a portion of the area of highest response is formed by an insert connected to the face.

9. The wood-type golf club head of claim 8 , wherein a majority of the face is formed of a second material having a thermal modulus response that is different from a thermal modulus response of the material of the insert.

10. The wood-type golf club head of claim 7 , wherein the material is formed in a first molecular phase at ambient conditions, and the heat generated by an impact of a golf ball on the ball striking surface at about 90 to 130 ft/s is sufficient to cause a portion of the material local to an impact site to undergo a heat-induced phase change to a second molecular phase, the second molecular phase having a lower modulus than the first molecular phase.

11. A wood-type golf club comprising the wood-type golf club head of claim 7 and a shaft connected to the head.

12. A 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 located proximate a center of the ball striking surface, wherein at least a portion of the area of highest response is formed of a material, the material being formed in a first molecular phase at ambient conditions, wherein heat generated by an impact of a golf ball on the ball striking surface at about 90 ft/s or more is sufficient to cause a portion of the material local to an impact site to undergo a heat-induced phase change to a second molecular phase, the second molecular phase having a different modulus than the first molecular phase, and wherein that heat generated by the impact of the golf ball on the ball striking surface at about 90 ft/s or more is sufficient to reduce a modulus of the material by at least 10% relative to the modulus of the material at ambient conditions; and

a body connected to the face and extending rearward from the face.

13. The golf club head of claim 12 , wherein the material has a first modulus due to heat generated by an impact of a golf ball on the ball striking surface at about 90 to 130 ft/s and a second modulus due to heat generated by an impact of the golf ball on the ball striking surface at about 160 ft/s, the second modulus being no more than 5% different from the first modulus.

14. The golf club head of claim 13 , wherein the material is formed in the second molecular phase as a result of the impact of the golf ball on the ball striking surface at about 90 to 130 ft/s and is also formed in the second molecular phase as a result of the impact of the golf ball on the ball striking surface at about 160 ft/s.

15. The golf club head of claim 12 , wherein the material forming the at least a portion of the area of highest response is formed by an insert connected to the face.

16. The golf club head of claim 15 , wherein a majority of the face is formed of a second material having a thermal modulus response that is different from a thermal modulus response of the material of the insert.

17. The golf club head of claim 15 , wherein the insert is located behind the ball striking surface, such that an entirety of the ball striking surface is formed of the first material.

18. The golf club head of claim 15 , wherein the insert forms at least a portion of the ball striking surface.

19. A golf club comprising the golf club head of claim 12 and a shaft connected to the head.