THE EFFECT OF STRETCH DIRECTION ON THE WRINKLING OF ORTHOTROPIC MEMBRANE

Every day, we use different objects in the shape of thin sheets or membranes. Papers, plastic bags, wrappings, and different kinds of textile, such as cloths, tents, and rugs, are among the best examples of membranes. Moreover, in most cases, the mechanical strength of these objects is their best characteristic. Safari or awning tents, parachutes and sports costumes are examples of membranes whose applications are somehow mechanically oriented. Yet, much more specifically, in many instances, the membranes are not isotropic. Good examples of these cases are polymeric synthetic cloths and thin rolled sheets of metal. One of the main aspects in the behavior of membranes is their wrinkling phenomenon. In fact, these objects cannot withstand different kinds of loadings, such as compressive and shear forces, as well as bending moments and, consequently, are very susceptible to a mode of failure known as wrinkling. There are different approaches to studying the mechanics of membranes. Many strategies used in these studies are based on the assumption of plane stress conditions. Obviously, these studies must assume that membranes cannot carry shear or compressive forces. One of the main approaches in this category is the Roddeman method. The method pointed out in the paper is used to analyze the wrinkling of an orthotropic membrane. Down to their structural composition under stretch forces, these types of membrane are more vulnerable than their isotropic relatives. The results obtained by using the theoretical approach of Roddeman are represented in the form of different tables, graphs and figures. In this analysis, both assumptions of small and large fields of deformation are used. The analytical modeling and solutions are supported by different simulations obtained using ABAQUS software. The results reveal how the change of loading direction can affect the orientation of the wrinkles. Moreover, the effects of load level and anisotropy on the depth of the wrinkles are studied.