1. PROCESSING OF COMPOSITES
Processing and Fabrication

2. POLYMER MATRIX COMPOSITE

3. INTRODUCTION
PMC are much easier to fabricate than MMC or CMC whether a thermoplastic or thermoset
Due to relatively low processing temperatures required to fabricate PMC.
For thermosets, such as epoxy, phenolic, and furfuryl resin, the processing temperature typically ranges from room temperature to about 200°C
For thermoplastic polymers, such as polyimide (PI), polyethersulfone (PES), polyetheretherketone (PEEK), polyetherimide(PEI), and polyphenyl sulfide (PPS), the processing temperature typically ranges from 300 to 400°C.

4. Fibre tow (continuous)
Materials
Intermediate stages
Component Production
Thermoplastic
Chopped fibre
Thermoset
Fibre tow (continuous)
Moulding compound
Impregnation
Weaving, braiding, etc.
Injection Moulding
Compression Moulding
Pultrusion
Filament winding
Resin injection
Schematic overview of approaches employed in fabrication of PMC

5. Difference in processing behaviour
Used as polymer matrices for carbon fibres
Curing performed in presence of heat & pressure
Thermoset resin hardens gradually due to polymerization and crosslinking (slow prodessing)
Thermoset
Greater ductility & processing speed than thermoset
Higher speed = amorphous thermoplastics soften immediately upon heating above the glass transition temperature (Tg), and so the softened material can be shaped easily
Can withstand to higher temperature compared to thermoset
Thermoplastics

6. Short Fiber/Particulate
FABRICATION PROCESS :
Mixing fibres/particles & liquid resin → slurry
Thermoset liquid resin = unpolymerized/partially polymerized matrix
Thermoplastics liquid resin = molten polymer/ polymer dissolved in a solvent

7. Molding into composite
Thermoset:
compression molding
matched die molding (applying a high pressure and temperature to the slurry in a die to harden the thermoset)
casting of the slurry into a mold is not usually suitable
because the difference in density between the resin and the fibers causes the fibers to float or sink unless the viscosity of the resin is carefully adjusted.
to form a composite coating, the fiber-resin or particle- resin slurry can be sprayed instead of molded.

8. Thermoplastics:
injection molding (heating above the melting temperature of the thermoplastic and forcing the slurry into a closed die opening through the use of a screw mechanism)
extrusion (forcing the slurry through a die opening via a screw mechanism)
calendering (pouring the slurry into a set of rollers with a small opening between adjacent rollers to form a thin sheet)
thermoforming (heating above the softening temperature of the thermoplastic and forming over a die using matching dies, a vacuum or air pressure, or without a die using movable rollers)

9. Unidirectional fiber parts with a constant cross-section (round, rectangular, pipe, plate, I-shaped)
Pultrusion
fibers are drawn from spools, passed through a polymer resin bath for impregnation
gathered together to produce a particular shape before entering a heated die
Suffer from poor mechanical properties in the transverse direction (i.e., perpendicular to the direction of pultrusion)

10. Continuous fibers various orientations
hand lay-up of unidirectional fiber tapes or woven fabrics and impregnation with a resin.
the molding – bag molding:
placing the tapes or fabrics in a die and introducing high pressure gases or a vacuum via a bag to force the individual plies together

11. Continuous fibers woven fiber fabric
Fabric may be impregnated with the resin or the polymer prior to being stacked and consolidated to form a composite
Stacking is in the absence of a resin and then the resin in infiltrated into the stack – a process known as resin transfer molding (RTM)
RTM is attractive in that it allows the fabrication of composites of intricate shapes
In RTM, a fiber preform (usually prepared by weaving or braiding and held under compression in a mold) is impregnated with a resin
The resin is admitted at one end of the mold and is forced by pressure through the mold and preform
The resin is subsequently cured

12. This method is limited to resins of low viscosity, such as epoxy
Problem with this process:
the formation of surface voids by the volatilization of dissolved gases in the resin
the partial evaporation of mold releasing agent into the preform
the mechanical entrapment of gas bubbles

13. PROBLEMS OF IMPREGNATION
After resin application:
Melt impregnation:
produce solid thermoplastic from solidification
produces a thermoplastic prepreg that is stiff and lacks tack
Solution impregnation:
produce solid thermoplastics from evaporation
produces prepregs that are drapeable and tacky
drapeable and tacky character of thermoplastic prepregs made by solution impregnation is comparable to that of thermoset prepregs
*Prepreg : pre-impregnated fibres where matrix such as epoxy is already present*

14. Both amorphous and semicrystalline thermoplastics can be melt processed, but only the amorphous resins can normally be dissolved.
Because of the high melt viscosities of semicrystalline thermoplastics (due to their long and rigid macromolecular chains), direct melt impregnation of semicrystalline thermoplastics is difficult.
Hence, the main problem with resin impregnation occurs for semicrystalline thermoplastics

15. SOLUTIONS TO PROBLEMS OF IMPREGNATION
Commingling of continuous reinforcing fibers with continuous thermoplastic fibers performed on;
fabric level :
yarns of different materials are woven together (co-weaving)
yarn level:
yarns of different materials are twisted together
fibre level:
fibers of different materials are intimately mixed within a unidirectional fiber bundle

16. Problems of commingling:
During processing (such as compression molding or filament winding), the thermoplastic fibers melt, wet the fibers, and fuse to form the matrix.
There is a preferred orientation in the thermoplastic fibers due to the spinning process used in their production, and this may be a problem.
The thermoplastic fibers have a tendency to form drops during heating.
In addition, the availability of high-temperature thermoplastic fibers is limited. PEEK is most commonly used for commingling with carbon fibers.

17. Fiber-matrix adhesion in a commingled system depends on
the molding temperature
residence time at the melt temperature
cooling rate
This is probably due to several complex mechanisms such as:
matrix adsorption on the fiber surface
matrix degradation leading to chemical bonding
interfacial crystallization

18. One method of forming continuous fiber composites in the shape of cylinders or related objects is filament winding:
involves wrapping continuous fibers from a spool around a (commonly cylindrical) mandrel.
fibers are wound in various predetermined directions (e.g., 90°) relative to the axis of the mandrel.
winding pattern is a part of the composite design.
Problem: Since the composite is very strong in the fiber direction, filament winding results in a cylindrical article that resists radial expansion, as needed for pressure vessels.
fibers can be impregnated with a resin before or after winding.

19. Processing parameters that need to be controlled:
the temperature of the mandrel
the impregnation temperature of the resin
the impregnation time
the tension of the fibers
pressure of the fiber winding

20. Explain these processes in detail and the resultant manufactured products. Include appropriate sketch
Hand Lay Up - Shafiq
Bag Molding – Azman, Salman
Filament Winding – Mariah, Azizan
Pultrusion – Shazwani, Mohd Akmal
Resin Transfer Molding – Affan, Azizul
Compression Molding - Zafuan
Injection Molding - Azlee
Extrusion – Amir Syafiq, Mohd Shahil
Thermoforming – Syahmi, Amir
Calendering – Zulaikha,

21. Major polymer matrix composite fabrication processes

22. Hand Lay Up
Fibers and resin are placed manually on a open mold, made of wood, metal, or reinforced plastic, consisting of a flat surface, a cavity, or a convex shape.
Reinforcements are usually glass-fiber mats, fabrics, or woven rovings, while resins are polyesters and epoxies.
The mold usually requires some preliminary preparation with a releasing agent
in order to facilitate removal of the composite part after the resin consolidation (cross-linking).

23. Procedure can be partially automated in a process1
A specially formulated layer of resin (called the gel coat) is initially deposited on the open mold 2
Resin mixture is applied to the reinforcement and compacted by using appropriate rollers
in order to remove any entrapped air as carefully as possible
Procedure can be partially automated in a process
(called spray-up) in which chopped fibers and resin are deposited simultaneously on the open mold by a special spray gun

24. Bag Molding
Starting product for the bag molding = prepreg (i.e., pre-impregnate)
which usually consists of a thin reinforcement layer (in the form of unidirectional fibers or woven cloth) impregnated with a partially cured resin (generally epoxy) to a typical fiber volume fraction of about 50% resin reacting before the composite manufacture.
During curing resin initially flows out of the prepreg
resulting in a typical fiber volume fraction of about 60%, which is an industrial standard for many structural applications

25. Cut
Composite laminae are cut from the prepreg roll
Layers Positioning
Positioned on each other according to the desired laminate sequence while ensuring that the fibers are aligned in the specified direction
Setup Positioning
The uncured laminate is then positioned between a bleeder, a breather, and various membranes and release materials
Compaction
Assembly is then subjected to a combination of external pressure, vacuum, and heat to consolidate and densify the various layers into a compact laminate

26. Typical setup for autoclave bag molding

27. Filament Winding
Filament winding is a manufacturing process where continuous reinforcing fibers are wound on a mold, called the mandrel
The process can be used to manufacture objects with a surface of revolution, like tubes, pipes, pressure vessels, tanks, etc. In the case of cylindrical or conical open shapes the mandrel design is relatively simple
Problem:
Mandrel removal due to end closures

28. Filament winding process
Fibres are passed through a resin bath
Fibres are placed on mandrel with a certain winding angle, by a carriage device
The fabrication process is completed by the curing operation
Mandrel removal
Filament winding process

29. Schematic of filament winding process

30. Pultrusion Technique is a highly automated process
Manufacture of composite materials into continuous, constant-cross-section profiles, like rods, tubes, and various structural shapes
Fibre content as high as 65–70% by volume

31. Steps in pultrusion process
impregnation
Continuous fiber rovings and/or mats (generally of glass fibers) are pulled through a resin bath impregnator
shaping
Pulled through then into a shape pre-former
heating
Through heated die (elevated temperature)
Matrix resin undergoes rapid polymerization
cooling
Cooling in natural or forced air convection to a temperature level at which it can be gripped, pulled
cutting
Cut by a flying cut-off saw that enables the cutting without interrupting the continuous pull motion
Steps in pultrusion process

32. Schematic in pultrusion process

33. Compression Molding
Compression molding is a manufacturing process wherein a molding compound (charge) is pressed in a matched metal mold and forced to fill the cavity
Heat and pressure are then maintained until the composite charge solidifies
The charge can have two basic forms:
flat sheets, called sheet molding compound (SMC) invariably based on UP resin reinforced with chopped fibers mats
a doughlike mixture of short random fiber, resin, and filler, usually called bulk molding compound (BMC) or dough molding compound (DMC)

34. Resin Transfer Molding
Resin transfer molding is a process:
a fibrous pre-form is placed in the cavity of a closed mold (matched male and female parts)
certain amount of pre-mixed resin is transferred into the cavity by a pressure injection device
Depending on the resin system and on the part thickness, an appropriate cure cycle is determined in the mold in order to attain sufficient green strength for the part removal.
Final curing can be performed in an electric oven.
The RTM process can be employed to:
complex structures
large near-net shapes
at relatively low cost and with considerable time saving compared to conventional lay- up processes

35. Schematic of resin transfer molding process

36. CERAMIC MATRIX COMPOSITES

37. INTRODUCTION
Monolithic ceramics generally have reasonably high strength and stiffness but are brittle with low toughness
One of the main reasons for forming CMCs is to increase toughness
It was not until fibers and whiskers of ceramics such as silicon carbide were readily available that there was much interest in CMCs
Simply an extension of the powder route for producing monolithic ceramics

38. CMC categories
Toughened ceramics reinforced with particulates and whiskers
- brittle behavior
- Improvements in fracture toughness and strength
Continuous-fiber composites
- quasi-ductile fracture behavior
- Extensive fiber pull out

39. The development of CMCs has lagged behind MMCs and PMCs for two primary reasons:
Most of the processing routes for CMCs involve high temperatures and can be employed only with high temperature reinforcements.
Differences in coefficients of thermal expansion, α, between the matrix and the reinforcement lead to thermal stresses on cooling from the processing temperature. These stresses can lead to cracking of the matrix.

40. Chemical Vapour Deposition
Materials
Intermediate stages
Component Production
Liquid Metal
Ceramic Powders
Ceramic Fibre
Vapour compound
Green body
Reactive Processing
Sintering
Hot Pressing
Chemical Vapour Deposition
Schematic overview of approaches employed in fabrication of PMC

41. Processing Methods of CMC
Powder consolidation
Powder based-methods
- Hot pressing
- Sintering
Chemically based methods
Chemical Vapour infiltration
Sol-gel route
Polymer pyrolisis

42. PROBLEMS:
Difficulty in obtaining a homogeneous mixture of the two constituents
High proportions of the toughening phase cannot be easily achieved.
Additional problems with whiskers:
Whiskers tend to aggregate causing a significant reduction in the packing efficiency.
Damage to the whiskers can occur during mixing and pressing, particularly when cold pressing.
Because of the difficulties encountered in obtaining homogeneous mixtures by conventional powder processing, wet processing is sometimes favored. It is essential that the constituents remain deflocculated, i.e., well dispersed, in the slurry.
Deflocculation is achieved by control of the pH of aqueous solutions and by ultrasonic agitation of the slurry.

43. Hot Pressing Examples : Al2O3-ZrO2, TiB2-ZrO2,Al2O3-SiC Advantages:
Applicable to all ceramic materials
Achievement of low to zero porosity levels
Achievement of high densities
Disadvantages:
Basic limitations of rather simple shapes: blocks, plates, cylinders
High temperatures requirements. Such temperature must be 100oC to 200oC higher than for hot pressing matrix alone

44. Conventional method for the production of ceramic monoliths and for some SiC-reinforced composites
Involves:
Loading a graphite die with the material to be consolidated, either as a prepreg or as individual components (i.e. fibers placed by hand within a powder).
Die is then heated to high temperature (>1000◦C, machine capability typically >2000◦C) in an inert atmosphere.
High(er) pressures are applied to the material during heating or at temperature to facilitate the consolidation of the powder.
The die is then cooled for removal.

45. Hot Isostatic Pressing
Similar in nature to hot pressing (high T, P), but utilizes gas pressure for consolidation versus the uniaxial pressure applied in hot pressing
Allows for much higher pressures on the sample
Tapes are formed through filament winding, tape casting, or through slurry infiltration into a woven fabric.
The tapes are stacked in the desired configuration within a rigid mold.
Once the mold is loaded, it is sealed and then heated and pressurized using an inert gas.
Sealing the mold prevents gas intrusion within the sample.
There is little constraint on the shape complexity of the composite since the gas pressure is the same for all surfaces and directions

46. Reaction Bonding Advantages:
Cost-effectiveness.
Allows for increased formability, since metals can generally be plastically deformed around the fibers.
Higher density composite. Upon heat treatment in air, the metal oxidizes, and depending on the specific metal, will result in a given volume change. Ideally, volume expansion will fill porosity present in the sample, resulting in a higher density
Primarily applied to the formation of monoliths, but it has been successfully demonstrated with sapphire fiber reinforcements
similar in nature to DIMOX; however,in this process, all of the metal can be oxidized, leaving no residual metallic phase

47. The milling parameters are crucial to the final product.
Process involves combining a metal powder, such as aluminum, with an oxide powder,such as alumina.
The powders are attrition milled together to obtain the optimal size and shape of the metal powders, which enables complete oxidation of the metal without excess hydroxide production
The milling parameters are crucial to the final product.
Undermilling results in larger metal particles that may not oxidize completely,
Overmilling produces hydroxides on the surface of the powder which may not be removed until very high temperature, resulting in bloating due to gas formation.

48. Chemical Vapour Infiltration
Chemical vapor impregnation (CVI) is a method of infiltrating fiber architectures with matrix particles via the vapor phase.
Similar process to chemical vapor deposition (CVD) in terms of gas reaction,
Decomposition conditions in CVI are chosen for in-depth decomposition rather than coating the surface of the substrate.
CVI has been used for carbon and silicon carbide matrix formation.
Hydrocarbon gases such as CH4 are used for manufacturing carbon matrix composites
Decomposition of methyltrichlorosilane is used in the production of silicon carbide matrix composites

49. CVI equipment for the temperature gradient technique

50. METAL MATRIX COMPOSITES

51. Schematic overview of approaches employed in fabrication of MMC
Materials
Intermediate stages
Component Production
Ceramic particles
Liquid metals
Metal powder
Fibre tow
Co-spray
Thermal spraying
Fibre Coat
Stir casting
Extrusion
Squeeze Infiltration
Hot Pressing
Chopped fibre
Metal foil
Mono-filament
Metal Vapour
Schematic overview of approaches employed in fabrication of MMC

52. Introduction Commercially less advanced than PMC due to:
Difficulties
Expensive
Three types of fabrication methods:
Solid state fabrication technique
Powder metallurgy, (cold isostatic press, hot isostatic press) diffusion bonding
Liquid state fabrication technique
Squeeze casting, liquid metal infiltration, spray co-deposition
Solid-liquid process

53. Liquid Phase Processes
Ceramic particles incorporated into molten metalic matrix
Followed by mixing and casting into shaped components and billets for fabrication
Selection criteria of ceramic fibres:
Compatibie with matrix
Elastic modulus
Tensile strength
Density
Melting temperature
Thermal stability
Size and shape
Coefficiet of thermal expansion
cost

54. Liquid phase process Liquid metal-ceramic particulate mixing
Squeeze Infiltration/Casting
Melt oxidation
Liquid metal-ceramic particulate mixing

55. Squeeze Infiltration Process: Preform
Preheated fibrous preform positioned in mould
Designed with specific shape to form integral part of a finished product
Binder is used (Si based)
Infiltration
Infiltration of molten metal into the preform
Infiltrated using ram pressure

56. Advantages:
Enforcement of molten metal through small pores of the fibres preform ensure good wettability of the reinforcement by molten metal
Minimal reaction between reinforcement and molten metal
Free of common casting defects such as porosity and shrinkage cavities

57. Squeeze infiltration setup

59. Melt Oxidation Process
Ceramic preform form into final product shape by fabrication technique is continuously infiltrated by molten alloy as it undergoes reaction with a gas phase
High-temperature oxidation of the molten alloy in ceramic preform
Produce matrix material of mixture of oxidation reactant products and unreacted metal alloy
Advantages:
Form complex, fully dense composite shapes

60. Example: Al infiltration with Al2O3 and SiC
Al alloy ingot containing 3 – 10 wt% Mg placed on on top of permeable mass of Al2O3 or SiC
Alloy-ceramic assembly heated in atmosphere/nitrogen at temperatures between 1475oC and 1835oC
Spontaneous infiltration will take place, provided:
Alloy contains Mg
Temperature is at least 1475oC
Atmosphere is mostly nitrogen

61. Liquid Metal-Ceramic Particulate Mixing
Approaches developed for incorporation of ceramic particles into alloy melt:
Injection of powders entrained in an inert carrier gas into melt using injection gun
Addition of particulates into molten stream as mould is filled up
Addition of particulates to the melt via vortex by mechanical agitation
Addition of small briquettes (co-pressed aggregates of base alloy powder and solid particulates) to the melt followed by stirring
Dispersion of particulates in melt using centrifugal acceleration
Pushing of particulates into melt using reciprocating rods
Injection of particulates into melt the melt irradiated with ultrasound
Zero gravity processing (ultrahigh vacuum & high temperature)

62. Difficulties: Example
Agglomeration of ceramic particulates during agitation
Settling of particulates
Segregation of secondary phases in metallic matrices
Extensive interfacial reaction
Particulate fracture during mechanical agitation
Example
Al-Al2O3 system
Al-SiC system

63. High energy, High-Rate Process
Solid Phase Processes
Solid phase process
Powder Metallurgy
High energy, High-Rate Process
Diffusion bonding

64. Powder Metallurgy
Blending of rapidly solidified powders with particulates, platelets, or whiskers
Steps include:
Sieving of rapidly solidified powders
Blending with reinforcement phases
Pressing to ~ 75% density
Final consolidation by extrusion, forging, rolling or hot working methods

65. Involves the sintering of the metal matrix particles when these particles have been mixed with the filler
Sintering involves solid-state diffusion, which causes the metal particles to join to one another
Joining starts with the formation of a neck between two adjacent particles
As sintering progresses, the necks become wider, so that the porosity in the overall material becomes smaller.

66. Advantages Rapid solidification of powders
Allows development of novel matrix outside compositional limits indicated by equilibrium thermodynamics in conventional solidification processes
Can be used for consolidation of continuous filament-reinforced composites
Fibre tows infiltrated by dry matrix powder
Followed by hot isostatic pressing
Produces homogeneous distribution
Excellent over techniques such as casting and liquid melt infiltration (squeeze casting)
1- Blending stage
2- Cold pressing = green body
3- Hot pressing = higher or lower than matrix alloy solidus

67. High Energy High Rate Process
Consolidation of metal-ceramic mixture achieved through application of high energy over short period of time
Mechanical and electrical energy sources utilised
High-energy, high-rate pulse (1MJ/s) facilitates rapid heating of conducting powder in a die wth cold walls
Example : Al-SiC, (TiAl + Nb)-SiC
Advantages of short time at temperature approach:
Opportunity to control phase transformation
Control over degree of microstructural coarsening

68. Diffusion bonding
Common solid state welding technique for joining similar and dissimilar metal
Interdiffusion of atoms on surfaces of metals in contact at application of elevated temperature
Advantages:
Ability to process wide variety of matrix metals
Control of fibre orientation and Vf

69. Example of diffusion bonding process in MMC:
Metal alloy foil + Fibre arrays / Wire / laminas stacked in predetermined order
Metal/metal alloys & reinforcement chemically surface treated for interdiffusion Or
Coating of fibres by plasma spraying or ion plating to enhance bonding strength
Diffusion bonding
Diffusion bonding under vacuum condition is more effective than atmospheric condition

70. 1) Starting components:
Fibre mat and sheets foil
2) Ply formation:
Sometimes ply is consolidated
3) Plies are stacked
Hot pressed

71. Deposition
Involves :
Coating individual fibres in a tow with matrix material needed to form composite
Diffusion bonding to form consolidated composite
Techniques include immersion plating, plating, electroplating, spray deposition, CVD and PVD
Advantages :
Degree of interfacial bonding is easily controllable
Filament would thin and monolayer tapes can be produced, thus can easily fabricate unidirectional / angle-plied composite

72. Advantages over PMC
Higher temperature capability along with fire resistance
Greater transverse stiffness and strength
Excellent electrical and thermal conductivities

73. Commercial MMC

74. PROJECT
EXPLAIN ONE APPLICATION THAT CAN BE MADE OF THE MATERIALS BELOW. ELABORATE ON THE PROCESSING STEPS INVOLVED IN THE MANUFACTURING PROCESS. INCLUDE SUITABLE AND RELATED DIAGRAMS IN YOUR REPORT.
MMC
CMC
CARBON-CARBON COMPOSITE
THERMOPLASTIC MATRIX COMPOSITE
THERMOSET MATRIX COMPOSITE

75. MMC – ANUAR, SYAHID, AZMAN
CMC – SYAZWANI, AKMAL, LOKMAN
CARBON-CARBON COMPOSITE – JOHNYDY, HAFIZUDIN, HOOD, ZUL
THERMOPLASTIC MATRIX COMPOSITE – SYAFIQ, ASLAMIAH, AMIR SYAFIQ
THERMOSET MATRIX COMPOSITE- MARIAH, ZAFUAN ZULAYKHA