Introduction to polymer composites (Matrix ,dispersed phase & interface)

1. Introduction to Polymer
composites
Mohamed Mahmoud Abdul-Monem

2. Introduction
• Composites can be defined as materials that consist of two or more
chemically and physically different phases separated by a distinct
interface.
• The different systems are combined to achieve a system with more
useful structural or functional properties non-attainable by any of the
constituent alone.
• The basic difference between blends and composites is that the two
main constituents in the composites remain recognizable while these
may not be recognizable in blends.

3. • Most primitive man-made composite materials were straw and mud
combined to form bricks form building construction

4. Natural polymer composites

5. • Composite material is a material composed of two or more distinct
phases (matrix phase and dispersed phase) and having bulk
properties significantly different from those of any of the
constituents.
• Matrix phase is the primary phase having a continuous character.
• Matrix is usually more ductile and less hard phase.
• It holds the dispersed phase and shares a load with it.
• Dispersed (reinforcing) phase is embedded in the matrix in a
discontinuous form.
• Dispersed phase is usually stronger than the matrix.

9. Advantages of polymer composites
a) High strength
b) High stiffness
c) High fracture resistance
d) Good abrasion resistance
e) Good impact resistance
f) Good corrosion resistance
g) Good fatigue
h)Low cost

10. Disadvantages of polymer composites
a) low thermal resistance
b) high coefficient of thermal expansion.

11. Factors affecting properties of polymer
composites
1. Interfacial adhesion
2. Shape and Orientation of Dispersed Phase
3. Matrix properties
4. Concentration of dispersed phase
5. Size of dispersed phase

12. Factors affecting properties of polymer
composites
1.Interfacial adhesion
• To attain superior mechanical
properties the interfacial
adhesion should be strong.
• Matrix molecules can be
anchored to the fiber surface by
chemical reaction or adsorption

13. Factors affecting properties of polymer
composites
2.Shape and Orientation of Dispersed Phase
The shape of the reinforcing particles can be:
• Spherical,
• Cubic,
• Platelet,
• Regular or irregular geometry.

14. Factors affecting properties of polymer
composites
• 3.Polymer matrix
Varieties of polymers for composites are :
• Thermoplastic polymers,
• Thermosetting polymers,
• Elastomers,
• Blends.

15. Thermoplastic polymers
• Thermoplastics consists of linear
or branched chain molecules
having strong intramolecular
bonds but weak intermolecular
bonds.
• They can be reshaped by
application of heat and pressure
and are either semicrystalline or
amorphous in structure.
• E.g. polyethylene,
polypropylene, polystyrene

16. Thermoset polymers
• Thermosets have cross-linked or
network structures with covalent
bonds with all molecules.
• They do not soften but
decompose on heating.
• Once solidified by cross-linking
process they cannot be
reshaped.
• E.g. epoxies, polyesters,
phenolics, ureas.

17. Elastomers
• An elastomer is a polymer with the
property of viscoelasticity,
generally having notably low
Young’s modulus and high yield
strain compared with other
materials.
• Elastomers are amorphous
polymers existing above their glass
transition temperature, so that
considerable segmental motion is
possible.
• E.g Natural rubber, synthetic
polyisoprene, polybutadiene,

20. Polymer composites interface characterization
• The characterization of interface gives relevant information on
interactions between fiber and matrix.
• The mechanical properties of fiber-reinforced composites are
dependent upon the stability of interfacial region.
1. Micromechnical : fiber-pullout & micro-debond test
2. Spectroscopic : XRD & EDX
3. Microscopic: Opitcal microscope,SEM,TEM & AFM
4. Thermodynamics: wettability & contact angle.

21. Fiber pullout test Contact angle

22. Processing of Polymer composites
1. Hand lay-up
2. Bag molding
3. Pultrusion
4. Filament winding
5. Preformed molding
6. Injection molding
7. Spray up

23. Dental composites

24. Dental composites
Dental
composite
Resin matrix Fillers
Silane coupling
agent

25. Resin matrix

29. Thank You