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

7

Post-Buckling

Post-buckling is the load regime a structure enters after buckling (Figure 7.1). In several situations, dictated by robust design practices, externally imposed requirements, or even the degree of comfort a designer is willing to accept, especially for single load path critical structures, buckling may be taken to coincide with final failure. However, in general, there may be considerable load capacity beyond buckling before final failure occurs. This is true in particular for plates, which, in contrast to beams (Figure 7.2), may have significant load-carrying ability beyond buckling. This ability is often capitalized on to generate designs of lighter weight.

Figure 7.1 Post-buckled curved composite stiffened panel

Figure 7.2 In-plane load versus centre deflection for plates and beams

As is seen from Figure 7.2, after buckling (P/Pcr >1) the centre deflections of a beam increase rapidly compared with those of a plate. This means that, in a beam, high bending moments develop early in the post-buckling regime and will lead to failure. In a plate, on the other hand, the deflections increase more slowly with increasing load and the panel can withstand significant excursion in the post-buckling regime before the resulting bending moments become critical.

This ability ...