Journal of Microelectromechanical Systems
Ping Du; Chen Cheng; Hongbing Lu; Xin Zhang
Volume: 22, Issue: 1, Page(s): 44 - 53

DOI: 10.1109/JMEMS.2012.2213070

Dear all, 

Need Help.. 

I'm doing research in moisture absorption in adhesive bonding. I'm wondering how to differentiate and characterize the Fickian Diffusion and Non-Fickian Diffusion during absorption and desorption moisture.

Thank You 

A single strand of polymer is a chain of a large number of monomers.  The monomers are joined by covalent bonds, and two bonded monomers may rotate relative to each other.  At a finite temperature, the polymer rapidly changes from one configuration to another.  When the two ends of the polymer are pulled by a force, the distance between the two ends changes.  The polymer is known as an entropic spring.  These notes are developed as part of statistical thermodynamics to supplement the course on advanced elasticity. 

Hi, I am a new PhD student working on the vibration behavior of a thin polymer film. Specifically the film is an elastomer VHB 4910. The question that I have specifically is that initially the film is 500 microns thick. Upon the application of prestress, the film is stretched (clamped) and the film thickness decreases to 20 microns. Assuming that the thickness is uniform, how can I calculate the tension in the membrane? 

Thanks for any suggestions that you can provide, and happy new year!

I just attended USNCCM11, and heard from a presentation that there should be free code for polymer viscoplasticity model from M.C. Boyce.Unfortunately, I googled from half an hour and dowloaded nothing this afternoon. Can anybody give more info ?

Thanks in advance !

Hi,

I am searching on multiscale simulation of polymer/metal ( mechanical propertices).

Cohesive zone model is used for this porpose.

Is there another models that can use for this issue and using MD data as input?

Best regards,

Hamed

Dear All, 

Recently I have read some literatures on Molecular simulation of polymer. My interest is measurement of

mechanical properties of polymer through the uniaxial tensile test.    

I have a question about relatively large time scales in MD simulations of polymer and how to interpret MD

stress-strain results for FE modeling. In particular, in the literature it is mentioned that strain rate of

The Duke Soft Active Materials Laboratory directed by Prof Xuanhe Zhao is seeking a highly motivated postdoctoral fellow to study mechanics of polymers and hydrogels with applications in tissue regenerations. The work will be carried out in close collaboration with the Duke Orthopaedic Bioengineering Laboratory directed by Prof Farshid Guilak.

Can any one assist me with a Phd proposal on Polymer nanocomposites. I want to work on Thermomechanical characterization of a named thermoplastic polymer.I need help with a topic

The Institute of Polymer Engineering has 3 open positions as research assistants in three different fields of polymer research:

- nano polymer technology

- polymer injection technology

- polymer composite technology

Please find more details in attachements.

Regards,

Nicolas

Hi all,

I am currently working on micro-sphere model like the one used by Miehe, Ihlemann and Pawleski. I wonder if someone know a FEM code who use this type of model.

Thanks a lot

Joachim Guilie

i'm a new persone in this webside

i'de like to know more good things about Gurson model.

if u have any help

so , u can add me between ur friends

yacult273@hotmail.fr

thx for ur help  

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.