In a previous paper , we have demonstrated that a microcrystalline copper film well bonded to a polymer substrate can be stretched beyond 50% without cracking. The film eventually fails through the co-evolution of necking and debonding from the substrate. Here we report much lower strains to failure (around 10%) for polymer-supported nanocrystalline metal films, whose microstructure is revealed to be unstable under mechanical loading.

I wish to inform the imechanica community about my recent book,  Polymer Engineering Science and Viscoelasticity, Springer, 2008. THe book starts at the beginning and contains both the physics of polymers and the mathematics of viscoelasticity. It is also unique in the history of mechanics in being the (first ever?) father-daughter book. Those interested in polymer mechanics may find this a useful resource! It may be found in your library or further information can be found here
http://www.springer.com/chemistry/polymer/book/978-0-387-73860-4?details...

Hi all,

I'm trying to model a peel T test on a composite material composed of steel and polymer (polypropylen) on Abaqus 6.7. Between these parts, there are cohesive elements COH3D8.
I have a problem with my model and I don't understand it. You can visualize my results in attachs files.
For understand this draw, a few precisions:
The elements in white has just here to guide the materials.
In B (cf attachs files), the nodes are embedded.
In A I applied a velocity.
In C I applied rotation constraints and coupling constraints on all rotations and displacements.
My structure present a strange evolution in the red circle. I don't understand this.

A 1um-thick Cu film was deposited on Kapton 50HN substrate, with a thin Cr interlayer to improve adhesion. The specimen was in-situ annealed at 200oC for 30min after deposition.

This FIB image was taken after the specimen was uniaxially stretched to 50% and released.

A link for the paper: http://www.seas.harvard.edu/suo/papers/201.pdf

For the polymer-supported metal thin films that are finding increasing applications, the critical strain to nucleate microcracks ( εc ) should be more meaningful than the generally measured rupture strain. In this paper, we develop both electrical resistance method and microcrack analyzing method to determine εc of polymer-supported Cu films simply but precisely. Significant thickness dependence has been clearly revealed for εc of the polymer-supported Cu films, i.e., thinner is the film lower is εc . This dependence is suggested to cause by the constraint effect of refining grain size on the dislocation movability.

Determination of Strain Gradient Elasticity Constants for Various Metals, Semiconductors, Silica, Polymers and the (Ir) relevance for Nanotechnologies

Strain gradient elasticity is often considered to be a suitable alternative to size-independent classical elasticity to, at least partially, capture elastic size-effects at the nanoscale. In the attached pre-print, borrowing methods from statistical mechanics, we present mathematical derivations that relate the strain-gradient material constants to atomic displacement correlations in a molecular dynamics computational ensemble. Using the developed relations and numerical atomistic calculations, the dynamic strain gradient constants have been explicitly determined for some representative semiconductor, metallic, amorphous and polymeric materials. This method has the distinct advantage that amorphous materials can be tackled in a straightforward manner. For crystalline materials we also employ and compare results from both empirical and ab-initio based lattice dynamics. Apart from carrying out a systematic tabulation of the relevant material parameters for various materials, we also discuss certain subtleties of strain gradient elasticity, including: the paradox associated with the sign of the strain-gradient constants, physical reasons for low or high characteristic lengths scales associated with the strain-gradient constants, and finally the relevance (or the lack thereof) of strain-gradient elasticity for nanotechnologies.