Foam Stiffened Structure and Method of Making the Same

Abstract

A structure includes a skin and a foam member. The foam member has a molded contour, the mold contour being configured to provide tooled surface for the skin. When the skin is a composite skin, the foam member provides support for the skin so that the skin can be cured under heat and pressure. A method of making the foam member for a foam stiffened structure includes creating a mold having an interior cavity which resembles a desired shape the foam member. A subsequent step involves introducing a foam mixture into the mold. Next, the foam mixture is allowed to polymerize so as to expand and distribute within the cavity of the mold. The method further includes selectively controlling a density of the foam member in the mold. The foam member is at least partially cured. The foam member is assembled with a skin to produce the foam stiffened structure.

1 . A structure, comprising:
 a foam member, the foam member having an outer molded surface; and   a skin member located at least partially around the outer molded surface of the foam member;   wherein the outer molded surface of the foam member is configured to provide a tooling surface for the skin member during assembly of the structure.   
     
     
         2 . The structure according to  claim 1 , wherein the skin is a composite material. 
     
     
         3 . The structure according to  claim 1 , wherein the skin is a metallic material. 
     
     
         4 . The structure according to  claim 1 , wherein the foam member has a side portion left exposed such that the skin member only partially envelopes the foam member. 
     
     
         5 . The structure according to  claim 1 , wherein the foam member is adhesively bonded to the skin member with an adhesive layer, so that the foam member is capable of carrying a shear load upon the skin member. 
     
     
         6 . The structure according to  claim 1 , wherein a release agent is used to prevent the foam member from being in bonding contact with the skin member, so as to substantially prevent a shear load from the skin member from being carried through the foam member. 
     
     
         7 . The structure according to  claim 1 , wherein a density of the foam member is tailored so that the foam member is able to withstand a predicted pressure load that the foam member will experience during a curing cycle. 
     
     
         8 . The structure according to  claim 1 , wherein a density of the foam member is tailored so that a strength of the foam member is tailored to withstand a predicted load that the foam member will experience during the lifetime of the structure. 
     
     
         9 . The structure according to  claim 1 , wherein the skin is an airfoil shape. 
     
     
         10 . The structure according to  claim 1 , wherein the structure is an airfoil member for an aircraft. 
     
     
         11 . A method of making a foam member for a structure, comprising:
 creating a mold having an interior cavity which resembles a desired shape of the foam member;   introducing a foam mixture into the mold;   allowing the foam mixture to polymerize so as to expand and distribute within the cavity of the mold;   selectively controlling a density of the foam member in the mold; and   curing the foam member.   
     
     
         12 . The method according to  claim 11 , wherein the step of selectively controlling a density of the foam member involves allowing the foam mixture to free rise by not constricting a pressure within the cavity. 
     
     
         13 . The method according to  claim 11 , wherein the step of selectively controlling a density of the foam member involves using a lid member to restrict the expansion of the foam mixture. 
     
     
         14 . The method according to  claim 13 , wherein a vent opening is located in the lid member. 
     
     
         15 . The method according to  claim 11 , further comprising:
 applying a release agent in the cavity of the mold prior to pouring the liquid mixture into the pour opening.   
     
     
         16 . The method according to  claim 11 , wherein the step of selectively controlling a density of the foam member in the mold includes selectively sizing a vent opening in a lid member. 
     
     
         17 . A method of making a composite structure, comprising:
 manufacturing an at least partially cured foam member;   laying up an uncured composite skin onto an outer surface of the foam member such that the foam member acts as a tool for the uncured composite skin;   curing the composite skin while foam member supports the portion of the composite skin.   
     
     
         18 . The method according to  claim 17 , wherein the step of manufacturing an at least partially cured foam member comprises:
 creating a mold having an interior cavity which resembles a desired shape of the foam member;   introducing a foam mixture into the mold;   allowing the foam mixture to polymerize so as to expand and distribute within the cavity of the mold;   selectively controlling a density of the foam member in the mold; and   at least partially curing the foam member.   
     
     
         19 . The method according to  claim 17 , further comprising:
 applying an adhesive layer between the foam member and the uncured composite skin.   
     
     
         20 . The method according to  claim 17 , wherein the step of laying up an uncured composite skin onto an outer surface of the foam member is achieved with a fiber placement machine. 
     
     
         21 . The method according to  claim 18 , wherein the step of manufacturing an at least partially cured foam member further comprises:
 locating a rib within the mold.