Unconventional localization prior to wrinkles and controllable surface patterns of film/substrate bilayers through patterned cavities

Abstract

A novel bilayer is introduced, consisting of a stiff film adhered to a soft substrate with patterned holes beneath the film/substrate interface. To uncover the transition of surface patterns, twodimensional plane strain simulations are performed on the defected bilayer subjected to uniaxial compression. Although the substrate is considered as the linear elastic material, the presence of defects can directly trigger the formation of locally ridged and then folding configurations from flat surface with a relatively small compressive strain. It is followed by the co-existing phases of folds and wrinkles under further overall compression. This phase transition reverses the traditional transition of wrinkle-to-ridge/fold for defect-free substrates. It's also found that the onset of initial bifurcation is highly dependent on the spatial configuration and geometries of holes, since the interaction of defects allows more strain-relief mechanisms beyond wrinkling. Furthermore, a rich diversity of periodic surface topologies, including overall waves, localizations, saw-like and coexisting features of folds and wrinkles can be obtained by varying the diameter, depth and spacing of holes as well as compressive strain, which provides a potential approach to engineer various surface patterns for applications.

inCrease: an Approach for Particle Enhanced Soft Composite 3D-Printed Tactile Displays

“…This would enable interesting social touch interaction possibilities between a robot and a human by having the robot emulate human-like behavior (e.g. robotic goosebumps to indicate a robot's affective response) [12].…”

“…inCrease builds on the approaches introduced by Guttag and Boyce [7], who proposed PESC designs that consist of flexible materials that are supplemented with relatively hard materials, and by Liao et al [12], who suggested the use of flexible materials that contain cavities. Both approaches are based on the idea of integrating a matrix of either hard material or cavities inside a flexible substrate that allows for changes in surface topography under compression ( Figure 1).…”

“…Based on these initial tests, a second exploration was conducted, inspired by the work of Liao et al [12], in which two prints were made that featured rigid materials combined with cavities. Firstly to reduce the force necessary for compression, and secondly to aid in the forming of more pronounced textures.…”

Localized forming limit analysis of substrate-supported metals: Influence of yield-dependent necking bound angle

“…For example, Refs. [38][39][40][41] present considerations of wrinkling of stiff films and sheets; the work of Long et al 42 formulate adhesively contact mechanics of large deformation in substrate-supported sheets and Refs. [43][44][45] analyze the instabilities and bifurcation events in the presences of substrate materials.…”