Window skin panel and method of making same

Abstract

A lightweight, structurally strong skin panel having one or more optically transparent areas forming see-through windows, and a method of making same. A plurality of layers of pre-preg fiber tape comprised of a plurality of optically transparent fibers pre-impregnated with an optically transparent resin is positioned over a plurality of metal sheets, with each metal sheet having a plurality of openings where windows are to be formed. The pre-preg tape layers and the metal sheets are layered onto one another such that one or more of the metal sheets is sandwiched between a pair of the pre-preg tape layers. The assembly is placed in a molding tool, and the tool placed within a vacuum bag. A vacuum assisted resin transfer forming process is used, together with heating of the molding tool, to produce a high strength, lightweight, integrated skin panel having optically transparent window portions. The skin panel eliminates the bulky and heavy frame structure traditionally employed on aircraft windows and has sufficient structural strength to be used as a portion of the skin of a fuselage of an aircraft without the need for reinforcing frame-like elements around the window areas.

1 . A method of forming a high strength, structural window skin panel, comprising:
 using a plurality of metal sheets to form a frame structure, wherein each said metal sheet includes an opening defining a window area;   aligning said metal sheets with one another so that said openings are aligned to form a uniform window opening;   laying a plurality of generally optically transparent, fiber pre-preg tape layers pre-impregnated with an optically transparent resin against said metal sheets such that at least one of the metal sheets is sandwiched between a pair of said fiber pre-preg tape layers;   further arranging said fiber pre-preg tape layers to fully cover said uniform window opening while overlaying said metal sheets;   heating the metal sheet and the fiber pre-preg tape layers such that said optically transparent resin flows and wets the fiber pre-preg tape layers and the metal sheets; and   curing, the fiber pre-preg tape layers and the metal sheets such that the fiber pre-impregnated resin tape layers and metal sheets form an integrated, lightweight window skin panel having an optically transparent, single pane window portion, and having an allowable tension strength of at least about 40,000 pounds per square inch per ply of and in the frame panel.   
   
   
       2 . The method of  claim 1 , wherein the fiber pre-preg tape layers are each are comprised of glass fibers. 
   
   
       3 . The method of  claim 1 , wherein the resin comprises an optically transparent aliphatic epoxy resin. 
   
   
       4 . The method of  claim 1 , wherein the fiber pre-preg tape layers comprise fibers having an index of refraction matching an index of refraction of the resin. 
   
   
       5 . The method of  claim 1 , wherein at least one of the metal sheets comprises a metallic foil strip. 
   
   
       6 . The method of  claim 1 , wherein at least one of the metal sheets is comprised of aluminum. 
   
   
       7 . The method of  claim 1 , wherein at least one of the metal sheets is comprised of titanium. 
   
   
       12 . The method of  claim 1 , wherein the fiber pre-impregnated resin tape has a width of approximately 0.125 inch (3.175 mm) to about 12.0 inches (304.8 mm). 
   
   
       13 . A method of manufacturing a lightweight, structurally strong, integrated transparent window skin panel, comprising:
 providing a plurality of pre-preg tape layers each having fibers pre-impregnated with an optically transparent resin, the resin and the fibers being selected to have substantially the same index of refraction;   providing a plurality of metal sheets each having a plurality of spaced apart openings formed therein;   arranging said metal sheets such that said spaced apart openings in each of said sheets are aligned to form a corresponding plurality of spaced apart window opening areas;   layering the pre-preg tape layers and the metal sheets onto a tool such that the metal sheets and the pre-preg tape layers are aligned one atop the other so that the pre-preg tape layers completely cover the openings and overlay a periphery of the metal sheets, with at least a pair of the pre-preg tape layers sandwiching at least one of the metal sheets;   heating the tool, the metal sheets, and the pre-preg tape layers so that the resin flows to cover portions of the metal sheets and wets the fibers in each of the pre-preg tape layers, the resin and fibers being substantially transparent to form a plurality of see-through window portions in the skin panel, with the skin panel having a structural strength sufficiently strong to be used as a portion of a fuselage skin panel of an aircraft.   
   
   
       14 . The method of  claim 13 , wherein providing the pre-preg tape layers pre-impregnated with a resin comprises providing a plurality of pre-preg tape layers each pre-impregnated with a transparent, aliphatic epoxy resin. 
   
   
       15 . The method of  claim 13 , wherein providing a plurality of metal sheets comprises providing a plurality of aluminum sheets. 
   
   
       16 . The method of  claim 13 , wherein providing a plurality of metal sheets comprises providing a plurality of titanium sheets. 
   
   
       17 . The method of  claim 13 , wherein the fibers are comprised of glass fibers. 
   
   
       18 . The method of  claim 13 , wherein providing a plurality of pre-preg tape layers comprises providing a plurality of pre-preg tape layers each having a width of approximately ⅛″ (3.175 mm) to about 12″ (304.8 mm). 
   
   
       19 . The method of  claim 13 , further comprising placing a caul plate atop the metal sheets, the pre-preg tape layers and tool. 
   
   
       20 . The method of  claim 19 , further comprising placing the caul plate, the metal sheets, the pre-preg tape layers, and the tool into a vacuum bag and removing the air therein. 
   
   
       21 . The method of  claim 13 , using an autoclave to heat the tool, the metal sheets and the pre-preg tape layers. 
   
   
       22 . The method of  claim 21 , wherein the autoclave heats the tool, metal sheets, and the pre-preg tape layers to approximately 250 degrees Fahrenheit under approximately 100 to 200 psi of pressure; and
 wherein the tool, metal sheets and the pre-preg tape layers are allowed to cure at a temperature of about 250° F. for approximately 3-5 hours.