The document discusses various topics related to composite materials including: 1. Composites are made of two or more materials combined to take advantage of distinct properties of each material. Fibers include glass, carbon, and synthetic fibers while matrices include polymer, metal, ceramic, and carbon. 2. Nanocomposites contain at least one constituent with dimensions less than 100 nm which can improve properties at the macroscale. Common nanofillers include clays, carbon nanotubes, and silica. 3. In situ polymerization involves dispersing nanoparticles in a monomer and polymerizing to form a thermoset composite with strong interfaces between the polymer and reinforcement.

1. AMINA.P.E
2nd M Sc BPS
CBPST, KOCHI

2. Introduction to composites:
 Definition:A composite material can be defined as a
macroscopic combination of two or more distinct material
having arecogenisable interphase between them.
 It consist of a continuous phase & discontinuous phase.
 continuous phase is called matrix & discontinuous phase is
called reinforcement, which is stronger than the
continuous phase

3. Category of fibers &matrix for
composites:
 Fibers:
Natural fibers
Synthetic organic fibers
Aramid fiber
Polyethylene fiber
Synthetic inorganic fibers
Glass fibers
Alumina fibers
Boron fibers
Carbon fibers
Si C fibers
Whiskers(SiC is available in the form of whiskers, i.e., small
single crystals):A few tens of microns in length and less than
one micro in diameter.

4.  Matrix:
Polymer (polymeric composites)
Metals (metal matrix composites)
Ceramic (ceramic matrix composites)
Carbon (carbon/carbon composites)

5. Nanocomposites:
 Polymer nanocomposites are also called polymer nanostructured materials.
 They are materials of which composition includes at least one constituent with
dimensions less than 100 nm.
 Their feature is that the nanoscale constituents can drastically improve and/or
modify properties and functionality of the macroscopic material.
 A challenge in developing the nanocomposites is to make exceptional
properties (mechanical, optical, etc.) of the nanomaterials obvious at the
micro- and macroscale levels of the hosting bulk materials.

6. Nanoparticle classification:
 Isodimensional or zero-dimensional; the same size in all directions;
aspect ratio is close to unity (L/D ~1). examples: spherical silica,
metallic nanoparticles, carbon black, fullerenes.
 Fibrillar; examples: carbon nanotubes and cellulose nanofibrils.
 Layered; examples: clay mineral and synthetic.
 The most common nanofillers used (inorganic):
Clays,
Carbon nanotubes,
Carbon black,
Fumed silica,
Cellulose-based fibrils as organic nanofiller.

7. Basic preparation methods:
 Solution dispersion,
 Melt dispersion,
 Sol–gel processing,
 In situ polymerization,
 Self-assembly (layer-by-layer technique).

8. What is In Situ?
In situ is a Latin phrase which translates literally
to 'In position'.
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9. What is In –situ technique?
 Involve a chemical reaction resulting in the formation
of a very fine and thermodynamically stable
reinforcing phase within a matrix.

10. In -situ polymerization process:
 Nanoparticles are dispersed in a liquid monomer or
relatively low-molecular-weight precursor as well as in
their solution.
 When a homogeneous mixture is formed, initiator is added
and it is exposed to appropriate source of heat, light, etc.
 The polymerization performed in situ results in the
nanocomposite.
 Polymers thus synthesized are called thermoset.

11.  Polymerization can be processed either within a mould cavity or
in some other in situ situation.
 Thermosets are usually covalently cross-linked that does not
allow them to reshape. They can be reused by granulating and
using as a filler.
 Nylon-6 was first used to develop nanocomposites by in situ
polymerziation of caprolactam monomer.
 Epoxy, phenolic, bismaleimide and cyanate polymers as
thermosets are applied to manufacture nanocomposites.

12.  To promote the crosslinking process, the curing of these
polymeric material usually needs the use of a hardener or
catalyst.
 In a case, for example, epoxies, such cross-linkers as
amines, anhydrides, and Lewis acids are applied.
 The disadvantage of use of curing agents is that they
modify the physical properties and influence the
functionality of nanocomposites.

13. Advantages :
• There is thermodynamic compatibility at the matrix-
reinforcement interface.
• Also, the reinforcement surfaces are likely to be free of
contamination~ Therefore, stronger matrix dispersion bond
can be achieved.
• Important for the preparation of insoluble and thermally
unstable polymer composites, which cannot be processed by
solution or melt processing.
• For preparation of polymer composites with high nanotube
loading, in-situ provides very good miscibility with almost any
types of polymers.

14. In -situ polymer processing:
• In-situ polymerization methods used to fabricate CNT-
PMMA composites by incorporating CNTs during the
course of polymerization of MMA.
• Basic starting materials:
1. Nanotubes
2. MMA monomer
• Method: In-situ free radical polymerization method
involves polymerization of monomer using a radical
initiator such as 2.2´-azobisisobutyronitrile (AIBN).
• CNTs are dispersed through ultrasonication in the
prepolymer.

15.  Adding CNT at prepolymer provides good dispersion in
the low viscosity of the prepolymer.
 As the polymerization progresses, the viscosity of the
solution increases and the polymer grows and wraps
around the dispersed CNTs.
 Benefits:
a) Higher interfacial strengths as CNTs interact with the
growing polymer, thus forming stronger CNT-polymer
bonds via non-covalent or covalent interactions.
b) Composites with enhanced mechanical, electrical
and tribological were obtained.

16. Ingot Metallurgy
(Synthesis of composites)
Al (99.9%) +
Ti (99.7%)
Graphite powder
(40-50 μm)
Heated
1100 °C – 1200°C
1h
1300 °C – 1400°C
10 minutes
Mixture direct chill
cast into ingot bars
Melt in
graphite-lined
induction
furnace with
argon gas flow.
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17. Example of ingot metallurgy:

18. PRECIPITATION

19. PMMA/GO COMPOSITE:
• The method for achieving controlled dispersion of graphene
oxide(GO) , in PMMA via the precipitation polymerisation
process in a water/methanol mixture.
• GO act as surfactant and adsorbs on the interface between
polymerised PMMA particles and solvent mixture.
• SEM confirmed that the precipitate consist of particles
surrounded by the GO sheets. Compression molding of the
precipitate yields a polymer nano composite with GO organized
into a regularly spaced 3D network which percolates at 0.2 wt %
GO.

20. DIAGRAM