This document discusses polymer matrix composites (PMCs). It defines PMCs and describes the two main types of polymer matrices: thermosets and thermoplastics. Thermosets cure irreversibly while thermoplastics can be remelted and reshaped. Common thermoset matrices include epoxies and unsaturated polyesters, while common thermoplastics include nylons and polyethylenes. The document also discusses different types of fillers/reinforcements like fibers, flakes and particulates that are added to polymers to improve mechanical properties. Finally, it examines different bonding mechanisms at the interface between the filler and matrix like mechanical, chemical, electrostatic and interdiffusion bonding that influence the

1. POLYMER MATRIX COMPOSITE
(PMC)
DR. KHAIRUL ANWAR ABDUL HALIM
2 OCTOBER 2018

2. Topic outcome
At the end of this topic, you should be able to :
• Evaluate the types of matrix in PMC
• Distinguish the types of filler in PMC

3. What is polymer
matric
composites?

4. Two component polymer-polymer
systems

5. Polymer Structure?

6. Thermoset
• Resins which readily cross-link during curing
• Curing involves
– Application of heat and pressure, or
– Addition of catalyst (curing agent/hardener)
3D network of chain

7. Thermoset- crosslink
– The strong bonds pulls the chains together.
– Restricts the movements of polymer chains
– Increase Tg to above room temperature, so thermosets are brittle at room
temperature and have low fracture toughness values.
– Thermoset cannot be reshaped by reheating, it degrades/ burn.

8. Thermoset
• Unsaturated polyesters (UPE)
• Vinyl esters (VE)
• Epoxies
• Phenolic (PF)
• Furan resins (FU)
• Polyimides (PI)
• Bismaleimides (BMI)

9. Thermoset
Source: http://www.mr-dt.com/
materials/thermosetting.htm

10. Thermoplastic
• Flow under stress at elevated temperature.
• Solidify and retain their shape when cooled to
room temperature.
• Recyclable

11. Thermoplastic Source: http://www.mr-
dt.com/materials/thermoplastics.htm

12. Thermoplastic

13. Source: https://tecnoelpalo.wikispaces.com/information+about+plastics

14. Thermoset VS Thermoplastic
Thermosets Thermoplastic
Resin cost is low Resin cost is slightly higher
Thermosets exhibit moderate shrinkage Shrinkage of thermoplastics is low
Interlaminar fracture toughness is low Interlaminar fracture toughness is high
Themrosets exhibit good resistance to
fluids and solvents
Thermoplastic exhibit poor resistance to
fluid and solvents
Prepregability characteristic are excellent Prepregability characteristic are poor
Prepreg shelf life and out time are poor
Prepreg shelf life and out time are
excellent

15. Thermoset VS Thermoplastic
Thermosets Thermoplastics
Young’s modulus (GPa) 1.3 – 6.0 1.0 – 4.8
Tensile strength (MPa) 20 – 80 40 - 190
Fracture toughness, KIC (MPa
m 1/2)
1.5 – 1.0 1.5 – 6.0
Maximum service
temperature (°C)
50 – 450 25 – 230
Fracture toughness: resistance of a material to the propagation of a crack

16. Filler/reinforcement
• Continuous fibers
• Filaments
• Chopped fibers
• Whiskers
• Flakes
• Particulate

17. Source: Jawaid, M.; Abdul Khalil, H.P.S. Cellulosic/synthetic fibre reinforced polymer hybrid
composites: A review. Carbohydr. Polym. 2011, 86, 1–18

19. Filler/reinforcement
Filler/
reinforcement
Example Effect
Reinforcing fibers Baron, carbon, fibrous
minerals, glass, Kevlar
• Increases tensile strength.
• Increases flexural modulus.
• Increases heat-deflection
temperature (HDT).
• Resists shrinkage and warpage.
Conductive fillers Aluminum powder,
carbon fiber,
graphite
Improves electrical and thermal
conductivity.
Extender fillers Calcium carbonate,
silica, clay
Reduces material cost
Aspect ratio: length to diameter ratio

20. Filler/reinforcement
Low-aspect fillers :
• Shrinkage will be less.
• Thermal resistance may be improved.
Strength, especially compressive strength, will
be improved.
• Impact resistance will often be lower than for
the unfilled polymer.
• Solvent resistance will often be improved.

21. Filler/reinforcement
High-aspect fillers : (aspect ratio >25, fibers)
• Strength is influenced by fibers orientation
• Shrinkage less in orientation direction as
compare to shrinkage in cross direction

22. Typical example

23. Factors which affect properties
• Proportion of matrix and filler
• Interface between matrix and filler
• Microstructure of composites
– Fillers: shape, size, orientation & distribution
– Matrix: grain size for polycrystalline matrices, etc.
• Homogeneity

24. Interfaces & Inter-phases in
composites
• The polymer matrix is relatively soft and
flexible
• The reinforcement must have high strength
and stiffness
• Since the load must be transferred from
matrix to reinforcement, the reinforcement-
matrix bond must be strong

25. Interfaces & Inter-phases in
composites
• Inter-phase
– a region where filler and matrix phases
are chemically and/or mechanically
combined.
– May be a diffusion/ nucleation/ chemical
reaction/ thin layer of fiber coating/ any
of the combination.
• Interface
– Boundary that separate the distinct
phases such as filler, matrix or inter-
phase

26. Interfaces & Inter-phases in
composites
• Filler-matrix interfacial adhesion influences the
mechanical properties of PMC.
• To promote the adhesion through:
– The removal of a weak boundary layer or
contaminations
– Improvement in wettability of filler surface by
thermoplastics
– Creation or addition of chemical groups
– Variation in surface topography (mechanical
interlocking)

27. Source:
Guigon M, Klinklin E. The interface and interphase in carbon fibre-
reinforced composites. Composites. 1994;25:534-9.

28. Types of interfacial bonding at
interface
• Mechanical
• Chemical
• Electrostatic
• Reaction/interdiffusion

29. Mechanical
• Interlocking / keying of two surfaces.
• More effective with rougher interface as interlocking is
greater.
• More effective if the force applied parallel to the interface
• Pure mechanical bond is not encountered but mechanical
bonding operates in conjunction with another bonding
mechanism

30. Chemical
• Bond formed between the chemical group on the
reinforcement surface and compatible groups in matrix
surface.
• Use of coupling agents. E.g: silanes (coupling oxide groups on
glass surface to molecule of polymer matrix).
• At one and of the silane molecule, hydrogen bond forms
between the oxide (silanol) groups on glass and the partially
hydrolyzed silane, whereas the other end it reacts with a
compatible group in the polymer.

31. Electrostatic
• Between matrix and reinforcement when one surface is
positively charged and other negatively charged.
• Leads to an electrostatic attraction between the components
of the composite which will depend on the difference in
charge on their surfaces.
• Interaction are short range and only effective over small
distances of the order of atomic dimensions
• Surface contamination and entrapped gases will decrease the
effectiveness of this bonding

32. Reaction / Interdiffusion
• Atoms and molecules of the two components of the
composite may interdiffuse at the interface.
• For polymer, it happens due to the intertwining of molecules.
• Controlled by the distance over which the molecules have
entwined, the extent of the entanglement of the molecules
and the number of molecules per unit area of interface.

33. References:
• Structural Composite Materials (available in
Knovel)
• COMPOSITE MATERIALS AND STRUCTURES
(http://www.ae.iitkgp.ernet.in/ebooks/)