Contact Mechanics of Layered Elastic Materials: Experiment and Theory

Published

January 26, 2007

Author(s)

P M. McGuiggan, Jay S. Wallace, Douglas T. Smith, I Sridhar, Z Zheng, K L. Johnson

Abstract

This paper reports an experimental and theoretical investigation of the indentation of a layered elastic solid, with special reference to the surface force apparatus (SFA). The contacting surfaces of the SFA comprise a 3-layer material: a thin mica surface layer on a thicker epoxy layer supported by a thick silica substrate. An existing finite element analysis of the deformation of ideal mica/epoxy/silica surfaces used in the SFA is adapted to compare with the experimental measurements of the variation of contact size with load, both with and without adhesion at the interface. This is in marked difference to the Johnson, Kendall and Roberts (JKR) theory for homogeneous solids. Experiments and finite element calculations were also carried out on the elastic indentation of a thin (5.5 gm) layer of mica on a very thick layer of epoxy (>100 gm). As input data for the calculations, the elastic moduli of the mica and epoxy were measured in separate indentation experiments. The stiffness to indentation of a layered solid can be expressed by an 'effective modulus,' E*, which has been deduced from the experimental measurements and compared with the theoretical values with fair success. The work of adhesion is commonly measured in the SFA by observing the 'pull-off force' to separate the surfaces. The theory shows that, for a layered solid, the pull-force can vary significantly from the JKR value for a homogeneous solid. In particular, it was found that the mica/mica adhesion is high, can vary with the pull-off force Fp according toFp/4 kR

Citation

Journal of Physics D-Applied Physics

Volume

40

Pub Type

Journals

Keywords

adhesion, contact mechanics, indentation, multilayer systems, Surface Force Apparatus

Citation

McGuiggan, P. , Wallace, J. , Smith, D. , Sridhar, I. , Zheng, Z. and Johnson, K. (2007), Contact Mechanics of Layered Elastic Materials: Experiment and Theory, Journal of Physics D-Applied Physics (Accessed October 20, 2025)