Mechanical properties of thin and thick coatings applied to various substrates. Part II. Young's modulus determination of coating materials*

Abstract

To determine Young's modulus of coating materials when they are applied to substrates, theoretical and experimental analyses are performed. Significant residual stresses are generated within thin and thick coatings applied to substrates. As a result of these stresses, the bi-material strip assumes a certain curvature. The curved beam theory was used to establish the equivalent bending stiffness of bi-layer materials as functions of (a) the initial radius of curvature generated by residual stresses, (b) the mechanical radius of curvature during flexure testing, and (c) mechanical (Young's moduli) and geometrical (widths and thicknesses) characteristics of bi-layered systems. The relevant expression was transformed to a second- or third-order equation in order to calculate Young's modulus of the coating undergoing residual stresses (using models developed in Part I and by Stoney, Röll, and Inoue).