Arthur Klein Lecture in Aerospace

The stability of structures continues to be scientifically fascinating and technically important. Shell buckling emerged as one of the most challenging nonlinear problems in mechanics sixty years ago when it was intensively studied, with Caltech being one of the leading centers of activity. The subject has returned to life motivated not only by structural applications but also by developments in life sciences concerning soft materials. Efforts are underway in the US, China and Europe to update existing design codes for shell buckling to take account of computational and experimental advances which have occurred in the last six decades, promising to enable significantly less conservative designs against buckling. The challenge is that shell structures are susceptible to catastrophic collapse and dramatic load-carrying reductions due to relatively small imperfections in their geometry. Imperfections must be factored into buckling load estimations. Most modern aerospace shells are either metallic reinforced with stiffeners or fiber reinforced composites, in each case manufactured to high levels of precision. This precision, and recent theoretical developments, have made it possible to design shell structures that are substantially lighter than those the design codes from 60 years ago allow. These developments will be highlighted in the seminar, complemented by a presentation of current experimental and theoretical work underway by the author and his collaborators on the imperfection-sensitivity of stiffened shell structures. Every attempt will be made to make the subject accessible to a broad engineering audience.