Design and Analysis of Composite Structures: With Applications to Aerospace Structures, 2nd Edition

9

Skin–Stiffened Structure

The individual constituents, skin and stiffeners, have been examined in previous chapters. Based on that discussion, the behaviour and the design of a stiffened panel such as the one shown in Figure 9.1 can be summarized as follows: The skin takes pressure loads via in-plane stretching (membrane action) and shear loads. It also takes compression loads up to buckling. Beyond buckling, extra care must be exercised to account for the skin deformations and additional failure modes, not examined so far, such as the skin–stiffener separation, which is discussed in this chapter. The stiffeners take bending and compression loads. It is readily apparent that the robustness and efficiency of a design will strongly depend on how one can ‘sequence’ the various failure modes so benign failures occur first and load can be shared by the rest of the structure, and how one can eliminate certain failure modes without unduly increasing the weight of the entire panel.

Figure 9.1 Stiffened panel under combined loads

In this chapter, some aspects that manifest themselves at the component level, with both skin and stiffeners present, are examined. This includes modelling aspects such as smearing of stiffness properties and additional failure modes such as the skin–stiffener separation.

9.1 Smearing of Stiffness Properties (Equivalent Stiffness)

If the number of stiffeners ...