Robert Cook, Principal Investigator

Slitting of Coated Webs

Many coated products are formed by first coating a wide (but thin) web or film and then slitting, cutting, or punching the web to yield a narrow tape or other shape much smaller than the original. Examples include:

• Thin polymer films coated with magnetic materials that are slit to form magnetic recording tape
• Thin polymer films coated with opticallysensitive emulsions that are slit and punched to form photographic film
• Paper multi-layer structures that are slit, cut, and punched to form adhesive labels
• Metal-coated polymer-ceramic composite sheets that are cut and punched to form multilayer chip capacitors or semiconductor substrates

A general problem of the slitting process associated with these coated products is maintaining or achieving a defect-free cut edge. Such edges are crucial for yielding products that maximize the useful surface area of the slit component.

The research team’s goal is to understand the slitting process so as to generate materials and process guidelines that optimize the edge quality of tapes formed by slitting. The investigation is in collaboration with Imation, which has appointed an IPrime Industrial Fellow who will implement several abaqus finite element models. They include “slitting” models (twodimensional and three-dimensional) with different cutting mechanisms (e.g., mode-III fracture, plastic flow, etc.), a mode III fracture model to simulate the crack in the magnetic supported layer, and a plane-strain mode-II “sliding” fracture model to study delamination. Explicit quasi-static analysis will be performed for some of the proposed “slitting” models. Elastic and viscoelastic material laws will be used in these models.

The project also includes testing of the different mechanical, fracture, and adhesive properties of the films to be studied. abaqus finite element models will also be used to complement the experimental work. In particular, a three-dimensional model of time-dependent deformation will be developed to describe depth-sensing indentation (“nanoindentation”) of multiplayer magnetic tapes. The models will allow elastic, plastic, viscous, and densification properties of the top, data storage, layer of the tape to be deconvoluted from load-displacement responses of the entire tape stack, and will provide insight into the contact mechanisms of porous materials.

Collaborator

Raul Andruet, Imation Corporation, Oakdale, Minnesota