Effects of periodic and localized imperfections on struts on nonlinear foundations and compression sandwich panels

Heuristic studies of a strut on an elastic foundation and a strut with a sinusoidally varying load are extended to include initial geometric imperfections. Examination of Various shapes of imperfection leads to the conclusion that for the majority of cases the most severe form is localized to a section of the structure rather than periodically distributed along the length. This leads to an examination of the imperfection sensitivity of an axially-loaded sandwich panel, the geometry of which is determined from a simple optimization routine bringing together two distinct modes of buckling. It is found that such a structure exhibits highly unstable snap-back behaviour in the perfect case and that combined with localized imperfections, it would never attain its linear critical buckling load. (C) 1999 Elsevier Science Ltd. All rights reserved.