JayS, good post as usual. A couple of minor corrections.
JayS wrote:Almost since 1920s, with the application of monocoque design approach, aircraft skins are always loaded structural members. It shifted to semi-monocoque design soon where skin has underlying reinforcements in the form of stringers and frames. In modern design for civil jet liners for example, upper and lower wing skin form the top and bottom part of the wing torsion box, the other two parts being front and rear spar. Likewise the fuselage skin is loaded completely.
Skin being thin metal/composite panels they don't take shear.
Actually membrane elements can resist in-plane shear...what you are referring above is transverse shear which membrane elements are not effective. Further, aircraft skin elements do not behave as pure membrane or as pure plate elements. Their actual behavior, just like many things in real life, is some where between the two.
JayS wrote:They only take up in-plane forces i.e. tension and compression. While its easy to load them under tension (think of stretched cloth), for compression they have reinforcing structural components below them (not the airframe structure but longerons circular frames, stingers etc >> semi-monocoque design)
Up to limit load, usually skin elements are effective in both tension and compression. Beyond LL, skins lose their effectiveness in compression, however skins in tension continue to be effective. As you have mentioned, longerons & stringers will continue to bear additional compressive load in fuselage while in Wing, the job is taken over by the spar & stringers.
In actual practice, it depends on what you are assumptions are during design phase about skin effectiveness (hence testing is necessary to validate your assumptions/mathematical models
JayS wrote:However now the parts are being manufactured in Pvt industry.
Saar, which Pvt. entity in India is fabricating composite panels?
The above post may be OT for LCA in general....