3.2 Challenges associated with structural analysis

  1. Safe (redundancies and no failure)
  2. Not over-designed (weight = cost)
  3. No room for error (get it right the first time)
    • Failure can be fatal
    • Re-design is extremely costly

3.2.1 Typical task

  • Givens:
    • Surface shape
    • Loads
  • Required:
    • Stiffness
    • Materials (based on flight envelope)

  • Constraints
    • Light weight!
    • Interior spaces
    • Manufacturing
    • Cost
    • Maintenance

3.2.2 Flight loads

  • Aerodynamic
    • Lift
    • Drag
    • Pitching moments
    • Torque
  • Thrust
  • Inertia
    • Landing
    • Gusts
    • Dynamic maneuvers
  • Vibrations

3.2.3 Weight drives geometry

  • Since the dawn of flight, weight has been a critical driving force
  • Requirements for lightweight structure drives structural efficiency (and selected design elements)
    • Well managed load paths are a key to efficient design
    • Local loads are transferred to principal structural components
      • Wing skins \(\Longrightarrow\) stringers \(\Longrightarrow\) ribs \(\Longrightarrow\) spars \(\Longrightarrow\) fuselage