Stress state, geometric considerations

Adhesive and adherend may exhibit considerable plasticity before failure and thus require nonlinear material models. In single lap joints, rotation of adherends occurs during loading, as illustrated in O Fig. 25.8, and geometrically nonlinear analysis is required to determine the correct stress state. 

The conformation of chemical groups characterizes the geometrical state of a polymer. Different conformations of a polymer can be produced by rotation about single bonds without rupture of chemical bonds. Changes in conformation arise from physical considerations such as temperature, pressure, or stress and strain. 

---