Now a yard long answer would be necessary, but the best review article in the last time is to your ask, I believe:

Estrin, Y., Vinogradov, A: Extreme grain refinement by severe plastic deformation: A wealth of challenging science, Acta Materialia, Volume 61, Issue 3, February 2013, Pages 782-817

http://ac.els-cdn.com/S1359645412007859/1-s2.0-S1359645412007859-main.pdf?_tid=d27a6522-dd26-11e4-a988-00000aab0f27&acdnat=1428412133_a15e2c22ef94bdbb284d6bb351835775

Cant answer - not enough data. 1) what kind of polymer? 2) what kind of particles? 3) what kind of modification? 4) what kind of prepare specimen? 5) what is the dispersion? 6) what is the 'manufacture' process? 7) we taking about elastomer or duroplast? and many other question. Usually with nano is the problem according to dispersion into polymer matrix. Nano may be modified with some special chemical groups - especially designed for. eg. phenolic resign. Not only nano may reinforce polymer. Think about small carbon fibres. Its really long story....

plasticity more pronounced in case of macro and micro as compared to nano level

Dear all 

I'm specifically asking about the plastic properties of mesoscale metals?

Thanks a lot for your participation

best regards

Sadeem

It is very clear that in nano size materials all physical intrinsic and extrinsic properties especially including the mechanical ones are strongly affected by the very existence of their surfaces.  As we all know!  the plastic behavior of metals and alloys  as a  response  to  the external tractions  and body forces are completely dictated and/or governed by the presence of  the bulk lattice imperfections. Better to say,  how they are reacting spontaneously  to these  external excitation in time and space.  For example in polycrystalline  micro and macro systems,   Hall-Petch connection between the mechanical strength and the grain size plays important role,  but below about 10 nm average grain size, the connection is replaced by an inverse connection, which tells us that decrease in grain size has detrimental effects  on the mechanical strength since the grain boundary sliding and rotation mode of plasticity  appear in scenario because of the grain boundary layer now behaves like a  greasy layer showing extremely low drag force against  the sliding and rotational motion of grains over each others. The result: SUPER PLASTICITY:  The elastic modulus is almost completely dictated by surface physical properties. Because of the extremely low density of gliding dislocation, and practically frozen their sources,  the shear modulus in single crystalline solids almost reach to the theoretical values, which means few orders of magnitude increase compared to the bulk counter part. 

An important change takes place also in the physico--chemical properties of thin film, which is the thickness dependence of the surface specific free energy that makes it possible for the formation of quantum dots and the wetting layer that has a thickness in  fraction of a nano meter in scale, which establishes the electrical connection between QD's. 

In Meso and Nano regions  palsticity effects are changed due to the changes in local mobility (e.g. mobility of dislocations etc.). Besides this also the "local" strain hardening

law will be changed by local effects. From this it follows that stress-strain plasticity

relationship changes. All the effects depend on the loacal structure and have to

be considered in a given material.  Hence there is no general law for the

change of plasic behaviour  when going fom macro to meso or nano dimensions.

B.Michel

Dear all

Thank you so much, but sometimes the deviation in results go sharply specially in plastic properties, take as an example the results that I got for one of the Aluminum alloys in mesoscale, I refer you to the question

https://www.researchgate.net/post/Can_the_strain_hardening_exponent_have_a_value_above_05

Dear Bernd; I am sorry to say that you are totally contradicting yourself  by spelling your last statement, unfortunately!!

Years and years I have heard from friends, who are top notch people in USA and Western European universities that have been  claiming that even for those thin films in the range of few hundreds of  NM thicknesses they show appreciable deviations from the elastoplastic  behavior according to the nano-hardness measurements. They proposed models such as the strain gradient motivated  micro elasticity-plasticity  theory (Gao& Nix) to explain the experimental measurements.  Even according to  the classic theory of linear elasticity plus the irreversible thermodynamics the spontaneous formation of the surface undulations and ripples are the main mechanism  for the relaxation of the stored elastic energy, the rate of which increases drastically with the surface to volume ratio.  Similarly internal friction and/or ultra sonic  measurements in single crystalline material shows that the surface states affects the modulus elasticity when you deal with nano scale systems, similarly the thermal and electrical properties show drastic change due to what they call '' the quantum confinement''  one has no longer quasi-continuum density of states but   high discrete energy levels accumulated at the conduction band lower edges. This directly affects the surface free energies thickness dependence, and generate what is called the wetting potential (isotropic & anisotropic) contribution in addition to the capillarity.   BEST REGARDS

Dear Prof. Tarek

Do you think that most of these properties of the nano and meso scale materials can be explained due to increase of the vibration energy of these particles at low scales?

Regards

Dear Sadeem,  the vibrational energy is strongly related to the temperature of the sample but if one thinks the enthalpy differences between the bulk and the surface layers then the size dependence  of average enthapy becomes clear. Since this dependence on the surface area S  to bulk volume  V  ratio R  by   assuming that the surface layer has invariant thickness one may read: R=  h S/V .  The result; definitely I expect some reduction in the overall enthalpy, and the decrease in the heat of sublimation because of  the fact that the surface atom has  about 1/3 less bonding to its immediate nearest neighbors!

I agree with you Prof. Tarik, In spite of there are many models considering the surface to volume ratio of nano materials but still they need to be connected to physics more deeply.

best regards

Sadeem

Dear Tarik,

I do not think that there are important contradictions between our opinions concerning

the  application of elastic-plastic relationships in the micro-nano regions.

I said, we must take into account local structure (dislocation based

structural effects or other ). There is no general law how to move from macroscopic

models to local ones without regarding the real structure of a given material. But in

many practical applications  continuum based modelling already leads to very good

approximations. We have a lot of very good examples for such approaches in

 Fraunhofer institutes together with industry mainly in micro- and nanoelectronics

 Bernd M.

Dear Bernd, I am sorry probably ı missed your points somehow since I thought you haven' t put enough emphasis on the role of imperfections not spelling that word strongly in your statements. Since we have had  completely different backgrounds such as  the Physical Science and Materials Science % Engineering  it is natural to look at  the same problems  from completely different perspectives, and labelled them using different terminologies.  For example,   I am very curies to know what do you mean by saying 'macroscopic model for elastic- plastic relationship?  Probably you mean the constitutive laws and equations extensively  used in continuum mechanics, which are claimed to be applied to any solids or fluids that deformed under the action of external forces. But these laws should obey strict restrictions such as they must obey the law thermodynamics, and satisfy the conditions of objectivity, or material frame in difference or Drucker stability criterion, etc.   I  am completely skeptic that  one of those constitutive laws operate when comes to know why and how any given material fails prematurely even though the applied loading few orders of magnitude smaller then the modulus o f rigidity.  Why some construction materials  collapsed catastrophically and others they did not when they exposed to Artic weather conditions even though there were no winds and no waves on the Sea?  

Dear All, in my opinion, there is no "the-only-one-approach" to the problem you are discussing. Please, see "logarithm properties vs. logarithm mean grain size" relationships... For some materials in some temperature intervals these relationships are straitforward absolutely (!). So, there is no subjest for the discussion at all! Before beginning this talk anybody has to be aware of what type of materials he/she talking about. Even, in the metal/alloy systems we observe very different behaviour...

Dear All colleagues!

Properties of a material at transition from nano to micro and mаcrо strongly differ (electric, optical and plastic too). Mechanical (including plastic) properties improve. They come nearer to theoretical values. Recollect threadlike crystals. Recollect the most ancient technology of the East of preparation by a sabre - Asian Chvorosan and Damask steel.

no idea

The main difference is nanoindentation gives the very localized hardness whereas micro-indentation gives the average hardness over the large area. For example, nanoindentation provides the hardness within the grain, microhardness is the mean value of different grains.