Length scale interactions in the folding of sandwich structures

Compressed sandwich structures, comprising thin stiff faces separated by a thick layer of a soft-core material exhibit behaviour analogous to the geol ogical phenomenon of parasitic folding in multi-layered media. Earlier cros s-fertilization of ideas from structural mechanics into structural geology is extended, by considering the interactions of folding on two different le ngth scales - overall buckling comprising a single half wave over the lengt h of the structure, combined with short wavelength local wrinkling of a sin gle face or layer. A new theory for such interactions is briefly presented and reviewed in the geological context. In the present problem, we see fold ing on different length scales at the same moment in time, implying a coupl ing of the instabilities associated with overall and local bucking. (C) 200 1 Elsevier Science B.V. All rights reserved.