In a message dated 8/10/2006 2:09:11 A.M. Central Standard Time, kyrilian_av@yahoo.com writes:

All of the comments are basically true.  Post-cure heat is used to raise the future temperature at which the epoxy starts to soften. Such a temperature is much higher than wet lay-ups that are not heat-treated after curing.  Panels, curved or flat, are stiffened by separating the BID skins with various materials.  For example, single BID per side 1/4" thick flat panels are very light and probably not used structurally.  Two BID per side 5/8" thick panels are very strong and much stiffer. 

 

Nomex honeycomb can be used because of its lightness, but it is less resistant to puncture wounds.  High density foam can be stronger, stiffer and slightly heavier and is often used for upper wing surfaces near the aircraft entry so those stiletto heels won't cause a problem on that surface.  Less dense foam can be used in other locations.  The fuselage, bulkheads and ribs may utilize the Nomex, although current flanged ribs and bulkheads (similar to cap strip construction) tend to be made of just glass without intervening BID separation since the flange itself adds enough stiffness.

 

All of these items are laid up in a mold (even the flat panels) where the final layers are dacron peel ply, cotton strips for air movement and plastic sheeting that is sealed at the edges and tapped for a vacuum to remove the air and squeeze everything together against the mold - thus vacuum bagging.

 

The resulting pieces are generically called "prepreg" just like kleenex is used for every nose doily manufactured.