bonding and composite process in sheet metal fabrication

1. BONDING & COMPOSITES
GROUP MEMBERS
MATHAN RAJ A/L MANIMAREN
THEVENDRAN A/L GUNASELAN

2. What is Composite?
Bonded
structure
using
chemical
methods
Combinations of 2
or more elements
– differ in
composition
Combinations
of 2 or more
elements –
differ in
identities &
properties

3. Multiphase material with significant proportions of
phases.
• Continuous phase (Matrix) – to transfer stress to
other phases and protect phases from environment.
• Dispersed/reinforcing phase – purpose is to enhance
matrix properties.
• Classification : Particles, fibers, structural.

4. ADVANTAGE
High Strength
to Weight Ratio
Customizable
Stiffness &
Strength
Corrosion
Resistance
High Fatigue
Resistance
Complex shape
built using less
mould
Ease of
Maintenance
Absorb radar
microwaves
(stealth
capability).
Simplify and
reduces
inspection
time.

5. DISADVANTAGE
Manufacture & repair cure time
Mechanical properties affected by temperature and moisture
Difficulty, reliability issue & cost in inspection
Low bearing and interlaminar strength
High material cost
Poor energy absorption and impact damage
May require lightning strike protection

6. MATRIX
Classification:
• Metal Matrix Composite (MMC)
• Ceramic Matrix Composites (CMC)
• Polymer Matrix Composite (PMC)

7. Polymer Matrix Composite (PMC) or Fiber-
Reinforced Plastics
• Fibers (discontinuous and dispersed phase) + plastic matrix
(continuous phase)
• Properties:
• Strong and stiff
• High specific strength (strength to weight ratio)
• High specific stiffness (stiffness to weight ratio)
(Brittle and abrasive, less toughness and chemically degradable when exposed
to the atmosphere)

8. • Percentages of fibers (by volume)–10% to 60% (limited by the average
distance between adjacent fibers)
• Highest practical fiber content is 65% ( higher percentage can lower physical
properties)
*Hybrid when more than one fiber is used.

9. REINFORCING FIBERS
• GLASS
• GRAPHITE
• ARAMIDS (KEVLAR)
• BORON
• Others
• (Nylon, Silicon Carbide, Silicon Nitride, Aluminium Oxide, Sapphire, Steel,
Tungsten etc.0

10. Fiber Size and Length
• Mean diameter < 0.01mm
• Oriented in longitudinal direction (strong and stiff in tension)
• Small cross section (low defects exist)
• Classified
• Short fibers (aspect ratio 20 – 60) : Improve mechanical properties as a result
of increasing the average fiber length.
• Long fibers (200 – 500) : transmit load through the matrix better, commonly
used in critical applications, particularly at elevated temperature.

12. Matrix Materials
• Thermosets – Epoxy (most commonly used ~ 80% of PMC), polyester,
phenolics, fluorocarbons, polyethersulfone, silicon and polyimides
• Thermoplastics –Polyetheretherketone

13. Functions
• to support the fibers in place, transfer stresses to them.
• to protect the fibers against physical damage and the environment.
• to reduce the propagation of cracks, by virtue the greater ductility
and toughness.

14. Properties of Reinforced Plastics
• mechanical and physical properties depends on :
• Type
• Shape
• Orientation of the reinforcing material
• Length of the fibers
• Volume fraction (%) of the reinforcing material

15. • type and amount of reinforcement effect the physical
prop. and resistance (fatigue, creep and wear)
• Highest stiffness and strength = fibers are aligned in
the direction of the tension force
• strength of the bond between the fiber and the
polymer matrix

16. Metal Matrix Composite (MMC)
• An alloy (Aluminium, Al-Lithium, Magnesium, Copper,
Titanium and superalloys)
• Three types of such composites
1. dispersion-strengthened - in which the matrix
contains a uniform dispersion of very fine
particles (10–100nm)
2. particle-reinforced – particles of sizes greater
than 1μm are present
3. fibre-reinforced - fibres may be continuous
through out the length of the component, or less
than a micro metre in length, and present at
almost any volume fraction, from 5 to75%.

17. • Reinforcement materials
• Graphite, Boron, Alumina, SiliconCarbide, AluminiumOxide,
Molybdenum, Tungsten

18. Advantages
1. Higher elastic modulus
2. Resistance to elevated temperature
3. Higher toughness and ductility
Disadvantage
1. Higher density thus greater difficulty in processing
the parts

19. Ceramic Matrix Composite (CMC)
Properties:
1. Strong and stiff
2. Resist high temperatures.
3. Lack toughness
Matrix materials (retain strength up to 1700 oC): Silicon
Carbide, Silicon Nitride, Aluminium Oxide and
Mullite(Al,Si,O2)
Carbon-CarbonMatrixComposites – strength up to 2500
oC (Carbon and Aluminium Oxide)

20. Fabrication of Composite Materials
• Particulate
• Laminar
I. Hot or Cold Roll Bonding
II. Explosive Bonding
III. Adhesive Bonding
IV. Sandwich Structures
• Fiber-reinforced

21. Processes Designed To Combine Fibers and
Matrix
• Prepregs
• Sheet Molding Compounds (SMC)
• Bulk Molding Compounds

22. Fabrication of Final Shapes from Fiber-Reinforced Composites
Pultrusion
• Continuous process that is used to produce simple shapes of uniform cross section
eg: round, rectangular, tubular, plate, sheet and structural products.
• Extremely high strengths products (reinforcement can be up to 75% of the final
structure).
• Crosssection – up to 1.5m wide and 0.3m thick.
Reinforcing fibers

23. Bundles of continuous
reinforcing fibers are
drawn through a bath of
thermoset polymer resin
The material is then
pulled through one or
more heated dies, which
further shape the product
and cure the resin
Upon emergence form the
heated dies, the product is
cooled by air or water, cut
to length and then
fabricated into products
e.g fishing poles, ski
poles

24. Resin-coated/ resin
impregnated, high
strength, continuous
filaments, bundles or
tape made from fibers
of glass, graphite, boron,
Kevlar or similar
materials can be used to
produce cylinders,
spheres, cones and
other container type
shapes that have
exceptional strength to
weight ratios
The filaments are wound over a
form or mandrel, using
longitudinal, circumferential, or
helical patterns or combination in
order to take advantage of their
highly directional strength
properties
By adjusting the
density of the
filaments in various
locations and
selecting the
orientation of the
wraps, products can
be designed to have
strength required and
lighter weight in less
critical regions
After winding, the part and
mandrel are placed in an
oven for curing, after
which the product is
stripped from the form
The matrix (epoxy
type) binds the
structure together
and transmits the
stresses to the
fibers

25. Final curing
Involving elevated temperature and possibly applied pressure
Multiple reinforcement sheets
Passed through a resin bath, faced with non stick sheet and passed through squeeze rolls.
For tubing
The impregnated stock is wound around a mandrel of the desired internal diameter
Pre preg sheets or reinforcement sheets
saturated in resin then compressed under pressure on the order of 7MPa.
Lamination and Lamination Type Processes
Laminated materials can be
produced as sheets
Tubes rods

26. Lamination
Type
Processes
Vacuum - bag molding
Air pressure holds the laminate against the mold while the resin cures.
Curing generally at room temperature but moderate elevated
temperature may be used
Pressure bag molding
A flexible membrane is positioned over the female mold cavity
and pressurized to force the individual plies together and drive
out entrapped air and excess resin
Compression molding
For large production quantities and high quality
The dies are heated and curing occurs during the compression
operation

27. Other processes
Spray
Molding
• No desired properties required.
• Mixing chopped fibers and catalyzed resin and spraying the combination on to a mold form.
• Rollers or squeegees can be used to remove entrapped air and work the resin in to the
reinforcement.
• Room temperature curing, sometimes elevated temperature is used to accelerate the cure.
Sheet
Stamping
• Thermoplastic sheets reinforced with non woven fiber–heated and press-formed.
Injection
Molding
• Chopped or continuous fibers are placed in a mold cavity that is then closed and
injected with resin

28. Fabrication of Fiber – Reinforced Metal Matrix Composites
Continuous fiber metal matrix composites can be produced by
variations of filament winding,
extrusion and pultrusion.
Fiber reinforced sheets can be produced by electroplating, plasma
spray deposition coating or vapor deposition of metal on to a fabric or
mesh, then shaped and bonded.

29. Fabrication of Fiber – Reinforced
Ceramic Matrix Composites
Common method includes chemical vapor deposition
or chemical vapor infiltration of a coated fiber base.
Hot pressing technique.

30. Secondary Process and Finishing
Can be processed further with conventional equipment (sawed, drilled,
routed, taped, threaded, turned, milled, sanded and sheared).
Precautions should be used to prevent the formation of splinters, cracks,
frayed or delaminated edges. Sharp tools, high speed sand low feeds are
generally required.
Quickly remove cutting debris–prevent cutters becoming clogged.
Abrasive materials (in nature)–dull most conventional cutting tools. Use
diamond or polycrystalline diamond tooling to achieve realistic tool life.
Use abrasive slurry–smooth surface.
Lasers and Water Jets as alternative cutting tools

31. Adhesive Bonding
A variety of joining methods can be used to provide the assembly
function.
Alternative joining methods include adhesive bonding, welding,
brazing, soldering, and mechanical fastening.
Adhesives are available in several forms:
liquid, paste, solution, emulsion, powder, tape and film.
• Adhesives thickness ~0.1mm.
• Adhesive application may be required due to the following properties.
a. strength (shear and peel)
b. toughness
c. resistance to various fluids and chemical.
d. resistance to environmental degradation (heat, moisture)
e. ability to wet the surfaces to be bonded

33. Design for Adhesive Bonding

34. Butt joint design Lap joint design

35. Strap joint design