The third lecture starts with a discussion on desirable attributes when designing structures.  For airframe structures, it’s pointed out that standard parts like skins, stringers, decks, etc. each have their individual failure modes.

 

Dr. C. Kassapoglou tells in stages how the design process should be carried out,  starting with the issue of obtaining the applied loads. Furthermore he pays attention to material variability, which leads to the usage of so-called A-basis and B-basis values, and material property degradation. Then asking to know the failure modes in advance to be able to make an accurate analysis, he then shows the difficulty of failure prediction, using lug and sandwich structure examples.

For the analytical analysis the governing equations of anisotropic elasticity are given. Finally an example of a plate under a point load on one end and a distributed load on the other was discussed.