Footwear sole structure having bladder with integrated outsole

1. A method of manufacturing a sole structure for an article of footwear, the method comprising:

forming a bladder having a first side formed from a first polymeric sheet and a second side formed from a second polymeric sheet, wherein the first polymeric sheet and the second polymeric sheet define a closed volume between the first side and the second side, and wherein the second polymeric sheet at least partially defines an outsole at the second side of the bladder, the outsole including a ground-contacting surface and a plurality of lugs; and

fusing a portion of the first polymeric sheet to the second polymeric sheet, wherein the fused portion extends from the first side of the bladder and is fused to the second polymeric sheet opposite the ground-contacting surface at the one of the plurality of lugs, the portion of the first polymeric sheet and the second polymeric sheet defining the one of the plurality of lugs.

2. The method of claim 1 , wherein forming the bladder includes:

vacuum forming the first polymeric sheet;

vacuum forming the second polymeric sheet to form the second side of the bladder and to at least partially define the plurality of lugs; and

wherein fusing the portion of the first polymeric sheet to the second polymeric sheet includes compression molding the portion of the first polymeric sheet to the second polymeric sheet.

3. The method of claim 2 , wherein compression molding the portion of the first polymeric sheet to the second polymeric sheet further includes mechanically urging the portion of the first polymeric sheet against the second polymeric sheet to form the one of the plurality of lugs.

4. The method of claim 2 , wherein the compression molding causes the one of the plurality of lugs to have a volume that is from about 10% to about 50% formed from the first polymeric sheet.

5. The method of claim 2 , wherein compression molding the portion of the first polymeric sheet to the second polymeric sheet further includes indenting the portion of the first polymeric sheet with a mold protrusion; and

wherein the indenting mechanically urges the first polymeric sheet and the second polymeric sheet to form the one of the plurality of lugs.

6. The method of claim 1 , further comprising:

providing a polymeric foam layer in contact with the first polymeric sheet and on an opposite side of the first polymeric sheet from the second polymeric sheet.

7. The method of claim 6 , wherein the portion of the first polymeric sheet that is fused to the second polymeric sheet forms a concave recess extending from the first side; and

wherein providing the polymeric foam layer includes filling the concave recess with a foamed polymeric material.

8. The method of claim 1 , further comprising pressurizing the closed volume.

9. The method of claim 1 , wherein each of the first polymeric sheet and the second polymeric sheet respectively includes a thermoplastic polymer; and wherein fusing the portion of the first polymeric sheet to the second polymeric sheet includes thermally bonding the first polymeric sheet to the second polymeric sheet.

10. The method of claim 9 , wherein the thermoplastic polymer is a thermoplastic polyurethane.