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MECHANICS - CASE STUDY

    Introduction


Aircraft Fuselage Loading

 

A new passenger plane is being designed with a composite fuselage skin. The fibers will be placed in four different directions; 1) along the length of the fuselage or longitudinal (long) direction, 2) around the circumferential (circ) direction, 3) 30o from the longitudinal fibers, and 4) -30o from the longitudinal fibers. The skin is made from multiple layers of graphite reinforced epoxy, but the fibers are only placed in the four directions as described.

What is known:

  • The stress in the longitudinal direction, σlong, is 50 ksi.
  • The stress in the circumferential direction, σcirc, is 25 ksi.
  • The twisting of the fuselage causes a shear stress, τtwist of 25 ksi.
     
    Question

   

What is the normal and shear stress in the direction of the 30o and -30o fibers?

     
    Approach

   
  • Using the stress analysis equations, rotate the stress state to plus and minus 30 degrees.
     
   
 
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