Morphological Instability, Buckling and Delamination of Multilayered Structures under Stress

Abstract

The mechanical properties of multilayered structures such as  stressed thin films on substrates,  pore channels or axi-symmetrical  precipitates embedded in a matrix has been widely investigated in the past few years because of the numerous technological applications of these structures in micro-electronics, material sciences or biophysics. In this talk, the roughness of the surface of stressed solids has been first investigated when surface diffusion is activated. The stability of the surfaces has been characterized for  a number of materials (nickel-based superalloys, axi-symmetrical conductors, etc.) as a function of the physical parameters of the materials and the applied stress.

The buckling and delamination of thin films deposited on polycarbonate substrates has been also investigated in the frame of the  F\^Ôoppl-Von Karman theory of thin plates. The formation of different patterns  such as straight-sided wrinkles, blisters, worm-like structures has been explained and the relevant parameters (critical stress, wavelength, size, etc.) have been determined and  compared to the experimental values obtained by atomic force microscope observations of  compressed metal thin films on polycarbonate substrates.

Experimental observations of the cracking of the interface of these coatings have  been finally reported and finite element calculations are
presented to explained the modification of the mechanical properties of the materials under traction stress.