EXPERIMENTS OF BUCKLING OF MULTILAYERS WHICH PERMIT INTERLAYER GLIDING

Multilayers in which the competent sheets can slip over one another, but in which the ease of sliding is not too high, have given rise to conjugate kink bands in the initial stage of deformation, irrespective of the nature of the embedding medium. The formation of kinks in these soft materials demonstrates in a striking way that kinking is not a result of brittleness. The wavelengths of the folds, for the same dimension of a multilayer, have increased with decreasing competency of the embedding medium. With increasing deformation the conjugate folds are transformed to chevron folds. This changeover has taken place at increasing values of shortening with decrease in competency of the embedding medium. With decreasing viscosity of the embedding medium the conjugate folds lose some of their angularity and take on smoothly curved forms at moderate shortening. Kink bands have not formed in multilayers with great ease of sliding. From the experiments a rough idea can be obtained about the physical conditions which favour developments of conjugate folds, chevron folds, concentric folds or intermixtures of these ideal types. © 1968.