Folding instability of a layered viscoelastic medium under compression

A preliminary theory is established for the stability of e visooelastio leyer sandwiched in an infinitely extended medium of another visooelastio materiel when s compressive force is acting in a direction parallel with the layer. The instability is menifested by e folding of the layer. It is shown that in general there exists e lower and & higher critical load between which folding occurs at a finite rate with a dominant wavelength. This is the wavelength whose amplitude increases at the fastest rate. Special ceses are also discussed in more detail such es that of e purely viscous layer in a viscous fluid, an elastic lityer in e viscous fluid, e viscous layer in en elastic medium, end of two Maxwell materials. Results indicate that the ratio of the relaxation times of the two materials is an important parameter.