Surface roughening of metal-polymer systems during plastic deformation

This paper concentrates on the evolution of roughness at the surface of a glassy polymeric coating that co-deforms with a metal under uniaxial strain. In experiments and simulations the roughness is described by three parameters: the rms roughness amplitude w, a correlation length xi, and a Hurst exponent H. In the plane strain simulations, the three stages (elastic, softening and hardening) in the stress-strain behavior of the polymer can be distinguished in their effect on the rms roughness amplitude w(epsilon). w(epsilon) decreases as a function of the thickness d of the coating for strains in the elastic and hardening regime. In the softening regime, shear bands originating at the interface intersect at a distance above the interface. In simulations, this leads to a distinct non-monotonous behavior of w(epsilon) as a function of thickness, with w(epsilon) reaching values above that at the interface at some thicknesses. In both experiments and simulations, it is found that the Hurst exponent H increases with increasing d. The correlation length xi at the polymer surface increases with increasing d in the simulations, whereas in the experiment an increase is observed only above a certain value of d. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved