FUNCTION OF STRUCTURAL COMPONENTS
The aircraft structure has a dual purpose:
a) It transmits and resists all loads applied to it, &
b) It acts as a cover to maintain the aerodynamic shape and protect its content.
The most efficient structure to achieve this is a thin shell structure supported by longitudinal
stiffeners and transverse frames, known as a semi-monocoque structure.
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Figure 7: Typical semi-monocoque structural component. (a) Body, (b) Aerodynamic surface. |
The function of the different structural members which go on to make an aircraft are as follows:
SKIN
1) It transmits aerodynamic forces to the longitudinal and transverse members.
2) It develops shear stresses to react the applied torsional moments
3) Together with longitudinal members it resists axial loads and applied bending
SPAR WEB
Similar to (2) for the skin
STRINGERS OR LONGERONS (with larger cross sectional area)
1) Resist bending and axial loads
2) Divide the skin into small panels
3) Act with skin to resist axial loads caused by pressurisation
SPAR CAPS
Similar to (1) and (2) of stringers.
FRAMES OR RINGS
These are the transverse members of the body, if they cover most of the cross section are
called bulkheads
1) Maintain cross sectional shape
2) Distribute concentrated loads
3) Establish column length to prevent buckling
4) Provide edge restraint for skin.
5) Act with skin to resist circumferential loads
