Adherence of Elastomers: Fracture Mechanics Aspectst

Abstract The adhesion forces which link two solids together are of the same nature as those which insure cohesion of solids (Van der Waals, ionic, covalent or metallic), and their thermodynamic transcription is the Duprr energy of adhesion w=γ 1 + γ 2–γ12, where γ2 is the surface energy and γ12 are interfacial energy. Its maximum value is about 2 J/m2 for strong binding. However, the force to separate two solids in contact (pull out force or adherence force) depends on a number of parameters including the shape of the solids in contact, their rheological properties, the withdrawal velocity, and the stiffness of the measuring apparatus (soft or hard machines). Adherence is thus characterized by a coupling between mechanics and surface effects and can be studied by fracture mechanics, a field where such a coupling appeared for the first time (Griffith, 1920).