A golf club head with a club head body having an external surface with a heel portion, a toe portion, a crown portion, a sole portion, and a front opening is described. A face insert support structure is located at the front opening. The support structure includes a peripheral member and a rear support member. The rear support member has a front surface and a rear surface. A face insert is attached at the front opening and closes the front opening of the body. An undercut fill structure is attached to a portion of the rear surface of the rear support member.
1. A golf club head comprising:
a hollow club head body having an external surface with a heel portion, a toe portion, a crown portion, a sole portion, an interior cavity, and a front opening, wherein the front opening opens to the interior cavity;
a face insert support structure located at the front opening, the support structure including a peripheral member and a rear support member, the rear support member having a front surface and a rear surface;
a face insert attached at the front opening and closing the front opening of the body;
at least two undercut fill structures attached to a portion of the rear surface of the rear support member;
wherein the at least two undercut fill structures each form a return angle with respect to a vertical x-z plane and are attached to one of the crown portion and sole portion;
wherein the front opening defines an aperture to an interior.
2. The golf club head of claim 1 , wherein the face insert includes at least a portion comprising prepreg plies having a fiber areal weight.
3. The golf club head of claim 2 , further comprising a metallic cap attached to the prepreg plies wherein the prepreg plies are configured to reinforce a majority of a metallic cap striking surface, the metallic cap abutting the transition edge to form a substantially flush golf club head front surface.
4. The golf club head of claim 3 , wherein the thickness of the prepreg plies is about 4.5 mm or less, and the thickness of the metallic cap is about 0.5 mm or less, and wherein the golf club head has a coefficient of restitution of at least 0.79 and a characteristic time of less than at least 257 μs.
5. The golf club head of claim 3 , wherein the metallic cap is comprised of a titanium alloy.
6. The golf club head of claim 2 , wherein the prepreg plies include carbon fiber reinforcement having a fiber areal weight of at least 100 g/m 2 , the face insert's total thickness is within a range of about 2.5 mm to about 4.5 mm.
7. The golf club head of claim 2 , wherein the prepreg plies have a fiber areal weight of less than 100 g/m 2 .
8. The golf club head of claim 1 , wherein the face insert's total thickness is within a range of about 1 mm to about 8 mm.
9. The golf club head of claim 1 , wherein the thickness of the face insert is non-constant.
10. The golf club head of claim 1 , wherein the peripheral member extends around at least a portion of a periphery of the front opening, and wherein the face insert is coupled to the peripheral member.
11. The golf club head of claim 1 , wherein the at least two undercut fill structures each substantially attaches to a tip portion of the rear support member.
12. The golf club head of claim 1 , wherein a front region of the crown is at least about 1 mm thick in a location where the at least two undercut fill structures attach to an interior surface of the crown.
13. The golf club head of claim 1 , wherein the at least two undercut fill structures each include at least three ribs spaced from one another.
14. The golf club head of claim 1 , wherein the at least two undercut fill structures include a transition radius between each undercut fill structure and at least one of the crown portion and the sole portion.