This document discusses the effect of nano-particle size on mechanical properties such as elastic modulus, hardness, strength, fatigue, and creep. It finds that elastic modulus is generally unaffected by nano-particle size, while hardness and strength increase with decreasing size due to grain boundary strengthening. Fatigue life and crack propagation rates improve by incorporating nano-particles, which reduce crack initiation and growth. Creep resistance is also enhanced in nano-composites due to restrictions on molecular chain movement. Overall, nano-materials exhibit enhanced mechanical properties compared to conventional materials due to their small grain sizes and interfacial interactions.

1. Effect of Nano-particle size
on Mechanical properties
Presented by
Maria Ashraf
Muhammad Ashraf

2. Introduction
Effect of Nano-particle size on Mechanical properties
 Elastic Modulus of Nano-material
 Hardness and Strength of Nano-material
 Fatigue and Creep of Nano-material

3. Introduction- What are nanomaterials?
• Nanomaterials are defined as materials in which on
of the dimensions (x, y, or z) is in the range (length
scale) of 1 – 100 nanometers (nm=m-9)
• The significance of decreasing grain size in order to
improve the mechanical properties of a material is
apparent in the production of ultrafine grain
materials (UFG) which have one dimension in the
order of 100-1000 nm. UFG materials are further
deformed to produce nanomaterials.

4. Effect of Nano-particles size on
Mechanical properties

5. Elastic Modulus
• An elastic modulus (also known
as modulus of elasticity) is a quantity that
measures an object or substance's resistance to
being deformed elastically (i.e., non-permanently)
when a stress is applied to it.

6. • Elastic modulus is of material is proportional to the
bond strength between the atoms or molecules.
• Structure independent and dependent on temperature
and defect concentration.
• A large increase in vacancy and other defect
concentrations can be treated as equivalent to higher
apparent temperature.
• If the temperature is increased, the mean separation
between the atoms increase and modulus decreases.
• Thus, the nanomaterials by virtue of their high defect
concentration, may have considerably lower elastic
properties in comparison to bulk materials.

7. • Nickel powder produced by electroplating with negligible
porosity levels had an E value comparable to fully dense
conventional grain size Nickel. Subsequent work on
porosity-free materials has supported these conclusions,
and it is now believed that the intrinsic elastic moduli of
nanostructured materials are essentially the same as those
for conventional grain siz materials until the grain size
becomes very small, less than 5 nm.

8. Hardness and Strength
• strength;-capacity of an object or substance to
withstand great force or pressure
• Hardness is material's resistance to any type of
deformation i.e. scratching, bending, compressing
etc. It is very easy to make a scratch in plastic than
that of steel because steel is harder.

9. • Strength and Hardness of nanostructured material
increases with decreasing size Grain boundaries
deformation

10. Fatigue
• Fatigue:- When component subjects to fluctuating
or repeated load, material tend to develop
characteristic behavior which is different from that
under steady load. Fatigue is phenomena which
lead to fracture
• Fracture take place under repeated or fluctuating
stresses whose maximum value is less than the
tensile strength of the materials(under steady load)
• Fatigue fracture is progressive beginning as minute
crake that grow under the action of fluctuating
stress

11. Fatigue failure is characterized by
three stages
• Crack initiation
• Crack propagation
• Final fracture
Addition of nano particles, results in an order of
magnitude reduction in fatigue crack propagation
rate for systems
Fatigue crack propagation rate can be reduced by
reducing the diameter and length and improving
their dispersion

12. The S-N Curve
• A very useful way to visual the failure for a specific
material is with the S-N curve.
• The “S-N” means stress verse cycles to failure, which
when plotted using the stress amplitude on the vertical
axis and the number of cycle to failure on the
horizontal axis. An important characteristic to this plot
as seen is the “fatigue limit”.
• Materials such as aluminium, copper and
magnesium do not show a fatigue limit;
therefore they will fail at any stress and
number of cycles

13. Creep
• Creep is the time-dependent permanent deformation
that occurs under stress, for most materials, it is
important only under, elevated temperature
• When materials subjected to creep, the materials
continue to deform until it’s usefulness is seriously
impaired.
• It is both a time & temperature dependent
phenomenon.
• Creep is probably the most widely studied long-term
property

14. Effect of Nano-particles in polymers
• Many studies shows that the addition of
nanoparticles to neat polymers can significantly
improve the creep resistance of the polymers at
various stress and temperature levels.
• During creep deformation, the molecular chains are
stretched and re-oriented.
• Creep behavior is affected by molecular weight,
degree of crystallinity, and the chemical resistance
of the polymer.

15. Creep curve

16. Creep behavior on CNT nano-composite

17. small grain sizes is responsible for low strain rates
and higher than expected creep resistance