Introduction to Polymer composites

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.

6. 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

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

8. Factors affecting properties of polymer composites Interfacial adhesion Shape and Orientation of Dispersed Phase Matrix properties Concentration of dispersed phase Size of dispersed phase

9. 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

10. 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 .

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

12. 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

13. 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 .

14. 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,

15. 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 . Micromechnical : fiber-pullout & micro- debond test Spectroscopic : XRD & EDX Microscopic: Opitcal microscope,SEM,TEM & AFM Thermodynamics: wettability & contact angle.

16. Fiber pullout test Contact angle

17. Processing of Polymer composites Hand lay-up Bag molding Pultrusion Filament winding Preformed molding Injection molding Spray up

18. Dental composites

19. Dental composites

20. Resin matrix

21. Thank You