Thermoviscoelastic Analysis of Polymeric Film on an Elastic Substrate with Graded Interlayer

摘要

A viscoelastic analysis of thermal stress in a polymeric film with a graded interlayer is presented. In this analysis, the material properties of the graded interlayer are assumed to change linearly from the substrate used to the film. Viscoelastic field was calculated utilizing a Laplace transform and then the viscoelastic stress of the film in a Laplace transform space was analytically inverted to obtain a time domain and to yield an expression as a function of relaxation time and elastic modulus and thickness ratios for the film, graded interlayer, and substrate. On the basis of the results of our analysis, the stress of the film rapidly decreased as the normalized times of the film increased. The effect of the ratio of film thickness to graded interlayer thickness was an increase in film stress as the ratio of substrate thickness to graded interlayer thickness decreased. As the ratio of film thickness to the graded interlayer thickness increased, the rate of stress relaxation decreased. Furthermore, as the ratio of film elastic modulus to the substrate elastic modulus increased, the rate of stress relaxation also decreased.