Wrinkling and Delamination of Thin Films on Compliant Substrates
Rui Huang (University of Texas at Austin)
Mechanics of Thin Films and Multilayered Structures
Tue 10:45 - 12:15
Salomon 203
When the surface of a soft material is coated with a stiff thin film, compression induced buckling instability of the thin film results in surface wrinkles, and wrinkling of the thin film may lead to fracture and delamination. In this talk, I will present a study on the mechanics of wrinkling and buckle-delamination for an elastic film on a very compliant substrate. First, with no delamination to begin with, an analytical solution is developed to predict onset of wrinkling, which takes into account the effect of Poisson’s ratio of the substrate. In comparison with a nonlinear finite element analysis, an approximate formula is derived to estimate the normal traction at the interface and to predict initiation of wrinkle-induced interfacial delamination. Next, with a pre-existing delamination, the critical strain for onset of buckling instability is predicted by finite element analysis, showing a smooth transition from wrinkling to buckle-delamination. For an intermediate delamination size, the critical compressive strain is found to be lower than previous solutions for both wrinkling and buckle-delamination. Post-buckling analysis by the finite element method shows a significant shear-lag effect with an effective load transfer length over three orders of magnitude greater than the film thickness. Finally, concomitant wrinkling and buckle-delamination is simulated to illustrate the interaction between the two buckling modes, and the results are discussed in view of predicting failure mechanisms as well as other applications of thin film materials.