Method and apparatus for forming a composite laminate stack using a breathable polyethylene vacuum film

Abstract

A method for forming a shaped composite structure. The method includes laying a composite laminate stack onto a mold, where the composite laminate stack comprises fabric laminate and resin and wherein the mold presents a predetermined shape, draping a vacuum film comprising polyethylene onto the composite laminate stack, thereby establishing an evacuatable volume between the vacuum film and the mold, applying suction to the evacuatable volume between the mold and the vacuum film to establish at least a partial vacuum within the evacuatable volume, thereby compressing the composite laminate stack via pressure applied to the vacuum film responsive to the at least partial vacuum within the evacuatable volume, and heating the composite laminate stack while applying suction to the evacuatable volume, thereby at least partially consolidating the laminate stack.

1 .- 8 . (canceled) 
     
     
         9 . A vacuum film suitable for use in compacting a composite laminate stack of at least two fiber layers against a mold, the vacuum film, comprising:
 polyethylene having a first surface and a second, opposing surface, and   a surface pattern, disposed on at least one of the first surface and the second surface, comprising a network of channels suitable for evacuating gasses from between the vacuum film and the mold.   
     
     
         10 . The vacuum film of  claim 9 , wherein:
 the vacuum film has a thickness of between 9.5 mils (0.24 mm)±10%;   the vacuum film is transparent to infrared electromagnetic radiation with a wavelength within a range of about 700 nm-1 mm   the vacuum film has a tensile elongation in a machine direction of between about 500-550%;   the vacuum film has a tensile elongation in a transverse direction of between about 650-700%;   the vacuum film has a tensile strength in the machine direction of between about 3300-3500 psi;   the vacuum film has a tensile strength in the transverse direction of between about 2700-2900 psi;   the vacuum film has an Elemendorf tear strength in the machine direction of between about 0.6-0.8 lb/mil;   the vacuum film has an Elemendorf tear strength in the transverse direction of between about 0.9-1.1 lb/mil;   the channels have a width of between about 11.2 mils (0.28 mm)±10%;   the channels have a depth of between about 6 mils (0.15 mm)±10%; and   the channels are disposed apart from one another by a separation distance of between about 84.8 mils (2.15 mm)±10%.   
     
     
         11 . The vacuum film of  claim 9 , wherein the surface pattern comprises at least one of a rectilinear grid pattern of the channels or a diamond pattern of the channels. 
     
     
         12 . The vacuum film of  claim 9 , wherein the vacuum film has a tensile elongation in the machine direction of about 525% and a tensile elongation in the transverse direction of about 675%. 
     
     
         13 . The vacuum film of  claim 9 , wherein the vacuum film has a tensile strength in the machine direction of about 3400 psi and a tensile strength in the transverse direction of about 2800 psi. 
     
     
         15 . The vacuum film of  claim 9 , wherein the vacuum film has an Elemendorf tear strength in the machine direction of about 0.7 lb/mil and an Elemendorf tear strength in the transverse direction of about 1.0 lb/mil. 
     
     
         16 . The vacuum film of  claim 9 , wherein the vacuum film resists deformation in a temperature range of at least one of between about 110-130° F. (43.33-54.55° C.), between about 115-125° F. (46.11-51.67° C.), or about 120° F. (48.89° C.). 
     
     
         17 .- 20 . (canceled)