Pressure balanced processing of composite structures

A method of processing a composite structure in an autoclave comprising:

• (a) laying up a composite structure on a mold, including the substeps of:
• (1) laying at least a first resinous composite ply on the mold;
• (2) placing an open-celled, low-density core on said at least a first resinous composite ply;
• and
• (3) laying at least one additional resinous composite ply over the top of said open-celled, low-density core such that said at least a first resinous composite ply, said open-celled, low-density core, and said at least one additional resinous composite ply form a composite structure;
• and
• (b) enclosing said composite structure within a vacuum bag;
• (c) curing said composite structure within said vacuum bag in said autoclave by applying to the exterior of said vacuum bag increased autoclave temperatures and autoclave pressures;
• (d) equilibrating the pressure within the cells of the open-celled, low-density core of the composite structure with the autoclave pressure being applied to the exterior of said vacuum bag during the curing of said composite structure;
• and
• (e) compressing the composite structure during the curing of said composite structure.

A method of pressure balanced processing of composite structures in an autoclave comprising:

• (a) laying up a composite structure on a mold, said composite structure comprising an open-celled, low-density core which is capable of collapse and which is surrounded by resin-impregnated fabric plies;
• (b) sealing a gas impervious vacuum bag over said composite structure and to said mold, said vacuum bag being penetrated by a port connected to a means to create a vacuum source;
• (c) curing the composite structure within the autoclave at autoclave temperatures and at autoclave pressures adequate to affix said fabric plies to said open-celled, low-density core;
• (d) equilibrating the pressure within the open-celled, low-density core in said composite structure with the autoclave pressure by penetrating said open-celled, low-density core with a tube open to said autoclave pressure and diffusing said autoclave pressure within said open-celled, low-density core;
• and
• (e) compressing the composite structure, during the curing of the composite structure, by creating with said vacuum source a pressure differential across said vacuum bag by evacuating from said vacuum bag volatile gases emitted into said vacuum bag by the curing of the composite structure.