Stretching-induced wrinkling in plastic-rubber composites

Area of Science:

• Materials Science
• Mechanics of Materials
• Surface Engineering

Background:

• Composite films with elastomeric cores and plastic surfaces exhibit complex mechanical behaviors.
• Surface texturing is crucial for applications in flexible electronics, sensors, and biomedical devices.

Purpose of the Study:

• To investigate the mechanics of wrinkle formation in three-layer composite films.
• To elucidate the role of plastic deformation in generating wrinkled surface textures.
• To determine the material property window for homogeneous wrinkle formation.

Main Methods:

• Experimental analysis of composite films (SEPS elastomer and LLDPE plastic) under uniaxial stretching and releasing.
• Finite Element Method (FEM) simulations to model the yielding, buckling, and post-buckling behavior of plastic layers.
• Characterization of wrinkle wavelength and aspect ratio in relation to stretching parameters and material properties.

Main Results:

• Stretching and releasing composite films induced significant wrinkling due to irreversible plastic layer yielding and reversible elastomer stretching.
• Wrinkle wavelength, on the order of 200 microns, decreased with increasing stretch ratio.
• FEM simulations confirmed plastic deformation at all stages, including yielding in tension, compression-induced buckling, and plastic hinge formation.
• Homogeneous wrinkles were predicted only within a specific range of material yield stress.

Conclusions:

• The study reveals a mechanism for generating highly wrinkled textures in composite films through controlled plastic deformation and buckling.
• This method enables the creation of high aspect ratio wrinkles (amplitude/wavelength > 0.4).
• Understanding the interplay between material properties and mechanical response is key to controlling wrinkle morphology.