Things to Know

1
Things to Know

• Review
• ISAT 430

2
Process-Property-Product-Performance Continuum

• Understand how
• Product performance
• Composition and structure
• Synthesis and processing
• Assumed behavior
• interact

3
Manufacturing Processes

• Know what the processes are doing
• Changing the state, geometry, physical
  properties, appearance,. Changing the value of
  the material
• Know that (in principle) manufacturing adds value
  to the material.

4
History

• For millennia, stuff was made
• One of a kind
• Labor intensive
• A person was a jack of all trades
• Material discovery drove manufacturing processes
• Wood
• Fibers
• Clay
• metals

5
History

• Industrial revolution (1760 1845)
• The steam engine
• Machine tools
• Textile machinery
• The factory system
• Other forces
• Eli Whitney interchangeable parts
• Henry Ford the assembly line

6
Conversion

• Extraction
• Bring it from the earth
• Cast or form
• Bring it to use

7
Manufacturing Processes

• Conversion
• Raw or natural to a more useful finished form
• Processing
• Transform a material
• Assemble
• Many parts into one.

8
Process Selection

• If you can find or discover a process, there are
  bases for the choice
• Technical
• Do not violate the laws of physics in our area of
  the known Universe
• Economical
• Can I do it and make a profit?
• Compatibility
• Know obvious incompatibilities
• Forging a plastic
• Blow mold aluminum

9
Process Selection

• Economics
• Numbers vs- cost
• Inspection
• Reduction in versatility
• Capital investment
• Conversion costs
• Environmental
• Waste production, release, and conversion costs
• Miscellaneous
• Material availability
• Time lines
• And all others, supply, labor, deadlines

10
The Effect of Numbers On Process Selection

• understand

The total cost of a batch of a given number of
pieces is
Where P total cost of a batch T cost of
tools and equipment n number of pieces in a
batch x the costs associated with each
individual piece
11
Processing of Polymers

• Know the three types of economic importance
• Thermoplastic
• Thermosetting
• Elastomeric
• Know their assets
• Light weight
• Corrosion resistant
• Electrically insulating
• Thermally insulating

12
Fluid Mechanics 201

• Understand viscosity and shear rate for a
  polymeric fluid

• The shear force per unit area is proportional to
  the local velocity gradient.
• The constant of proportionality is called the
  viscosity

This is Newtons law of viscosity
13
Shear Flow in a Cylinder

• Fluid velocity is zero at the wall.
• Fluid velocity remains constant on concentric
  cylindrical surfaces.
• The flow is purely axial
• The fluid velocity reaches a maximum at the
  center.
• This is called

Laminar Flow
14
Velocity Distribution in a Cylindrical Tube

• The fluid moves under the influence of a pressure
  gradient.

• There is friction, both
• at the wall of the tube
• Within the fluid itself
• Thus, the fluid is
• Accelerated by the pressure gradient
• Retarded by the frictional shearing stress

Pressure gradient
15
Shear Rates4

• Shear rate
• 0 at the center (r 0)
• Max at the wall (r R)
• Shear rate is an indication of the stress being
  seen by the fluid, and how fast it sees it!
• The shear rate at the wall for a Newtonian fluid
  is

Q volumetric flow rate D diameter
16
Volumetric Newtonian Flow in a Tube
The laminar flow of a Newtonian fluid in a pipe
or tube may be expressed
Where Q the volumetric flow rate m3/s
or gal/min ?P the pressure drop or driving
force kg/m2 or Pa R the radius of the
tube m or cm L the length of the pipe
m or cm ? the Newtonian viscosity
Pa s
17
Fluid mechanics -- viscosity

• Understand the effect of viscosity on pressure
  drop through a cylindrical pipe.
• Realize that for a Newtonian fluid, the viscosity
  is independent of shear rate
• But.
• Most polymeric fluids are not Newtonian
• Thus, the viscosity is NOT constant
• There is an important family of fluids called
  POWER LAW FLUIDS

18
Newtons Law of Viscosity
or
19
Power Law Fluids

• The deviation of n from unity indicates the
  degree of Non-Newtonian behavior.
• If n lt 1, material behavior is pseudoplastic
• If ngt 1, material behavior is dilatant.

20
Power Law Viscosity

• For most polymers, the isothermal viscosity
  decreases with increasing shear rate.
• Effect of shear on the entangled polymer chains
• Usually, in the literature, the viscosity is not
  shown as ?, but rather ?
• So

21
Viscosity

• Newtonian Fluid
• Viscosity (slope) constant
• Non-Newtonian Fluid
• Viscosity is not constant
• Profound affect on processing

22
The Effect of Shear Rate on Viscosity

• The effect can be enormous
• In this case the zero shear viscosity is about
  1000 Pa s.
• At a shear rate of 1000 sec-1, the viscosity has
  dropped to about 5 Pa s

23
Shear Rates
Power Law
n 1 Newtonian Law
24
Volumetric Flow Rates
N 1 Newtonian Fluid
Power Law Fluid
25
Synthetic Fibers

• Predates recorded history
• Early fibers were plant or animal
• Wool
• Silk
• Cotton
• Linen
• 1910 first commercial rayon
• 1938 nylon
• 1959 Lycra spandex
• 1974 Kevlar aramid

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Denier

• Measure of the fineness of a yarn
• Denier weight in grams of 9,000 meters of yarn
• Essentially a linear density

27
Spinning

• Things common to all spinning systems
• Metering pump
• Precise volumetric flow control
• Spinneret
• Extrusion of the filaments
• Spin cell
• Manipulation and protection of the forming
  filaments

28
Methods of Spinning fibers

• There are three main methods of spinning fibers
• Melt spinning
• Wet spinning
• Dry spinning

29
Melt spinning
Melt Spinning

• Not the oldest spinning method
• More straight forward
• removal of heat
• no solvents to worry about.
• Example -- nylon

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Melt spinning
Nylon

• Either cross flow or radial gas flow.
• staple yarn uses radial
• filament yarn uses crossflow
• Uniformity of the air flow is critical
• Minimum air necessary is used to reduce
  turbulence.
• Three forces resist the feed roll
• Resistive inertial
• Rheological stresses
• Aerodynamic or drag forces (important for
  spinning speeds gt 5000 m/min

31
Wet Spinning

• If a polymer
• does not melt
• dissolves only in non-volatile or thermally
  unstable solvents
• We wet spin
• Polymer solution is extruded into a liquid bath
• miscible with the solvent
• does not solvate the polymer.
• Example Kevlar

32
Wet Spinning
Kevlar Air Gap Spinning
Spinneret
Metering pump
To drying and constant tension winder
4 ºC water
Neutralization Washing bath
33
Dry Spinning
Dry Spinning

• Solution is extruded into a hot gas
• As the filaments pass down the cell, the hot gas
  causes the solvent to vaporize
• This process is complex
• Heat transfer
• Mass transfer
• through the filament
• into the gas
• Gas - solvent management
• Example Lycra

34
Dry Spinning
Hot Nitrogen (300 - 450 ºC) inserted
Polymer is dissolved in dimethylacetamide (DMAc)
and then pumped to the top of the cell
Gas is made uniform and Passes into the
filaments And Down The cell
Gas heats the solvent, driving It from the
filaments.
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Dry Spinning

• Near the bottom of the cell there is a vacuum
  box.
• The solvent rich gas is extracted.
• The solvent is recovered.

Long cell

• Just at the cell exit
• Recycle gas is inserted into the cell
• DMAc gt15 flammable
• Keeps solvent/gas from the room
• Acts as a curtain
• The fibers exit the cell and pass to the winders.

Vacuum Box
Recycle
36
Cell limits

• Drying rate limitations
• How fast we can transfer heat into the filaments
  and mass out of the filaments.

• Is the limitation

• How fast solvent can diffuse through the filament
  and across the surface

• The persistence of the solvent / gas boundary
  layer.

37
Fiber Tenacities
38
Fiber Elongation
39
Polymer Processing

• Processing Methods and Operations
• Choice is dictated by the product desired and the
  quantity desired.
• Fiber, film, sheet, tube
• Cup, bucket, car bumper, chair.
• Fiber manufacture is different, it is continuous.
• Large quantities usually use extrusion or
  injection molding
• Smaller quantities use compression molding or
  transfer molding

40
Extrusion

• Used mostly for thermoplastics
• Products
• Piping, tubes, hoses
• Window and door moldings
• Sheet and film
• Continuous filament (spinning)
• Coated electrical wire and cable
• Elements
• A hopper
• A barrel
• A screw

41
Extruder
Usually 1 6 in. dia.
Up to 60 rpm
The die is not part of the extruder
Flight clearance of only 0.002 in.
42
Screw details

• Helical flights with space between them
• Carries the polymer.
• Flight land is hardened and barely clears the
  barrel.
• The Pitch (distance the flight travels in one
  complete rotation) is usually about equal to the
  diameter.

43
Extruder details

• Understand melt flow in the extruder
• Flow forward occurs because of friction between
  the fluid and the screw flights.
• Axial flow (z direction) provides the pumping
• Cross flow provides the mixing

44
Extruder transport back pressure.

• This is the maximum possible output for an
  extruder.
• Conveyance of the polymer through
• Smaller and smaller cross sections
• the screen pack and die
• Creates a back pressure, Qbp.

45
Qnet is what finally comes out of the die!
46
Net flow

• Some parameters we control (design parameters)
• Some we cant control (operating parameters)

47
Design Parameters

• These we control at conception time and are fixed
  thereafter.
• Barrel diameter
• Flight or Helix angle
• Channel depth dc
• Barrel length L

48
Operating Parameters

• These we can fiddle with to optimize the process.
• Rotational speed, N
• The head pressure (change the die, slow the
  screw, change the temperature)
• The hidden variable TEMPERATURE.
• The viscosity
• But only to the extent that the shear rate and
  temperature will allow!

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Extruder characteristics

• A given extruder will have known operating
  characteristics.

or
50
Extruder Characteristics

• Flow up with
• Increasing N
• Decreasing p
• Increasing ?
• Ignores non-Newtonian flow behavior
• Ignores friction

51
Die Characteristics

• Flow through a die generates back pressure
• For a simple cylindrical flow channel the flow
  rate is given by the famous Hagen Poiseuille
  equation

D diameter ? melt viscosity
52
Die characteristics

• So flow increases with p
• Look at the power of the die diameter!
• This gives the linear die characteristic curve.
• Note some people write the above equation as

53
Extrusion Curve
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Stress Strain

• Curves obtained from tensile tests
• Information obtained
• Strength
• Ductility
• Toughness
• Elastic modulus
• Stiffness
• Range of workable properties

56
Stress -- Strain

• Know a lot about the material just from a glance
  at the S S curve
• Know the elastic region
• Understand strain hardening
• Grain boundary movement and blockage
• Understand the effect of temperature on the
  stress strain properties.

57
Know whats Going on here
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Composites

• Know what a composite is.
• Know the benefits of a composite
• Using different materials to affect the bulk
  properties
• Weight
• Strength

59
Composites

• Know the function of the matrix
• Know the function of the reinforcement
• Know the various types of reinforcement and why
  you would choose each
• Continuous
• Discontinuous
• particulate

60
Composites

• Have a knowledge of the various fibers used in
  most composites
• Glass
• Aramid
• Carbon and graphite
• Know difference
• Boron

61
Composites

• Understand the effect on properties that occurs
  using different types of reinforcements
• Understand the importance of the reinforcement /
  matrix interface / bond
• Understand anisotropy in composites and why it
  occurs

62
Composites

• The rule of Mixtures
• Know that it uses the volume fraction
• Know why
• Other types of composites
• Sandwiches
• Foam cores

63
FRPs..MMCs.. CMCs.

• Know the differences
• Advantages and disadvantages of each
• Applications for each
• General material used in each

64
Composite Processing

• Understand preforms
• Know the various ways of laying up a composite
• FRPs
• By hand
• Spray molding
• Filament winding
• Mandrels
• Helical, polar, braid
• pultrusion

65
Composite Processing

• MMCs
• Cermets
• Cemented carbides
• CMCs
• Mixing
• Compaction
• sintering

66
Metal Casting

• Know history (in general)
• Sand casting
• Know the process steps
• Investment casting
• Know the process steps
• Know the advantages of each

67
Phase Diagrams

• Understand phases
• Understand solutions and compounds
• Interstitial
• Substitutional
• Understand how phase diagrams are made
• Know what they are good for

68
Phase Diagrams

• Know what phases are present
• Function of composition
• Function of temperature

69
Phase Diagrams

• Understand and be able to use the inverse lever
  rule
• Ends of the line give the composition
• Ratios of the line tell how much of each

70
Heat Treatment

• Know the principal ways of heat treating
• Know why heat treating is done
• For the Fe C system
• Know where iron, steels, and cast irons exist
• Know what the various important phases of FeC
  are
• ? ferrite, ? iron, ? iron, austenite,
  bainite, Pearlite, and cementite

71
Heat Treatment

• Annealing
• Know the principals
• Martensite
• Know what it is,
• How it is formed
• What is its structure

72
Heat Treatment

• Understand the TTT curves
• Their uses
• How they work
• Quenching
• Why quench
• Why different fluids are used

73
Heat Treatment

• Surface hardening
• Know the common procedures
• Know the different uses

74
Extra Credit

• Be able to derive the matter energy
  relationship first proposed by Albert Einstein

• E ma2

• E mb2

• E mc2

Oh Yeah!!!!!!!!!!!!
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Dies

• The die determines the extruded shape
• Two important factors
• Die swell
• bambooing

79
Effect of Die Swell

• Knowing that die swell will occur is important
• After the polymer leaves the die it is rapidly
  cooling and becoming fixed in shape
• For each polymer, if we know
• Viscosity
• Temperature
• Shear rate
• We can account for the die swell in the shape of
  our die

80
Die shapes
The dies
The finished shapes
81
Pipe extrusion

• The central mandrel is supported by spider legs
• These disrupt the flow of polymer
• The polymer rejoins itself because
• the flow rate is low
• The conditions havent changed (temperature)
• To minimize the effect of the spiders, the
  mandrel is tapered.

82
Tubing Die

• Note the expansion to the spider legs and the
  reduction afterwards.
• If the extrusion is too rapid, the spider leg
  openings will not heal.

83
Wire Coating Die

• The wire runs straight through
• Polymer comes in vertically into a distribution
  cavity
• Used for wire diameters of 1 mm up to submarine
  cables with diameters of 150 mm.
• Wire helps to draw the melt through the die
• Coated wire speeds up to 10,000 ft/min

84
Injection Molding

• Polymer is heated, mixed, the then forced to flow
  into a mold cavity
• Similar to extrusion
• Hopper, barrel, screw
• Screw rotation is the principal motion only in
  one part of the cycle
• Mixes, compacts, plasticizes, and heats
• Pressures may reach 10 20 MPa (1450 2900 psi)
• In the injecting stage, the screw is driven
  axially by a piston to generate the working
  pressure
• 150 250 MPa (21,756 36,260 psi)

85
Injection Molding Sequences
(1) Close the mold
(2) Inject the melt
(3) Retract the screw
(4) Open mold eject part
86
Thermoforming

• A flat thermoplastic sheet is softened and
  deformed into the desired shape.
• Used for large items
• Bathtubs
• Skylights
• Freezer interior walls
• Bumpers
• Two steps
• Heating
• Deforming / forming

87

• Three major types of thermoforming
• Vacuum
• Pressure limit of 1 atmosphere
• Pressure
• Higher allowable pressures
• Mechanical

88
General plastic considerations
89
Product design Considerations

• In general
• Strength
• Plastics are not metals
• Should not be used in strength or creep critical
  applications.
• Impact resistance
• Good, better than many ceramics
• Service temperature
• Much less than metals or ceramics
• Degradation
• Radiation
• Oxygen or ozone
• Solvents
• Corrosion resistance
• Better than metals

90
Extrusion Considerations

• Desirable product traits
• Wall thickness should be uniform
• Hollow sections seriously complicate the
  extrusion process
• Corners
• Avoid as they cause uneven polymer flow and are
  stress concentrators

91
Forming and Shaping
92
Forming and Shaping

• Forming changing the shape of an existing solid
  body
• Shaping usually is creating a desired shape by
  casting or molding

93
Forming

• Rolling flat
• Plate, sheet, and foil
• Good surface finish
• High capital
• Rolling shaped
• Structural shapes, bar, I beams, t beams
• Shaped rolls, high capital
• Forging
• Production of discrete parts with a set of dies.
• Material is stamped
• Usually at elevated temperatures
• Some finishing is needed
• High capital

94
Forming

• Extrusion
• Long lengths
• Constant cross section (solid or hollow)
• Not real high costs
• Drawing
• Long rod and wire of some cross section
• Smaller cross section than extrusion
• Good finish
• Moderate costs

95
Forming

• Sheet metal forming
• Variety of thin shapes and sizes
• Moderate to high costs
• Can be complex

96
Shaping

• Powder metallurgy
• Compact
• Sinter
• Used to make pellets for diamond shots (except no
  sintering)
• Plastics and composites
• Involves molding, shaping, extruding, spinning
• Ceramics
• Similar to powder metallurgy
• Shaping and sintering (firing)

97
Rolling

• Rolling is a process to reduce the thickness of a
  long workpiece by compressive forces applied
  through a set of rolls.
• First developed in the late 1500s
• A steel ingot is cast into a rectangular mold
• Placed in a furnace while just solidified and
  held for many hours (36) until the temperature is
  uniform.
• This process is called soaking
• Furnaces are called soaking pits.
• Implies that properties will be uniform
  throughout the ingot and process that way.
• The rolling temperature for steel is about 1200C
• From here the ingot goes to the rolling mill.

98
Rolling

• Starting material depends upon what you are
  producing.
• Bloom
• Square cross section 6 x 6 in or larger
• Slab
• Rolled from an ingot or a bloom
• Rectangular cross section 10 x 1.5 in or more
• Billet
• Rolled from a bloom
• Square cross section 1.5 x 1.5 in or larger.

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Metal Behavior in forming

• As metal deforms, its strength increases (strain
  hardening)
• The strain rate is important
• Higher the rate, the higher the average metal
  stress
• The higher the temperature, the less the effect

102
Working temperatures

• Cold working room temperature
• Advantages
• Accuracy, good surface, some strain hardening, no
  heating
• Disadvantages
• High force and power needed, part must be clean,
  crazing or stress fracture is a concern

103
Working temperatures

• Warm working 0.3 0.5 Tm
• Advantages
• Low force and power, material is more ductile,
  annealing may not be needed
• Disadvantages
• Surface finish not as good, energy needed to heat

104
Working temperatures

• Hot working 0.5 0.7 Tm
• Advantages
• Low force and power, brittle material may be
  worked, properties are isotropic
• Disadvantages
• Localized melting (maybe), scale formation, lower
  dimensional stability, poorer surface, shorter
  tool life

105
Ring Rolling

• Ring is placed between two rolls, of which one is
  driven
• Volume of the ring is constant to the diameter
  increases during the process
• Ring blanks
• Cut from a plate
• Cutting a thick walled pipe.

106
Thread Rolling

• No loss in material
• Good strength (cold working)
• Surface finish is very good
• Process induces residual compressive stresses on
  surface which improves fatigue life.

107
Thread properties

• Machining cuts through the grains
• Rolling compresses them

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Joining
109
Joining Technologies

• Joining is a many splendored thing.
• Welding
• Arc or melting
• Resistance or other
• Soldering brazing
• Mechanical fastening (bolts nuts).
• Seaming and crimping
• Adhesive bonding
• All are important for different reasons.

110
Fusion Welding

• Oxyfuel gas welding
• Uses a fuel gas and oxygen to produce the heat.
• Arc welding
• Heating is accomplished by an electric arc
• Resistance welding
• Heating is accomplished by the passage of an
  electric current
• Others
• Electron beam and laser welding

111
Oxyfuel welding

• Most common fuel is acetylene, C2H2
• Flame temperature can reach 3,300C
• Flame heats the material
• Low efficiencies .1 -- .3
• Must control the fuel/oxygen mixture to protect
  the workpiece
• Cheap
• Good for repair jobs
• Low volume stuff

112
Fuel Temperatures and Heats.
Just know that there are different fuels and
obtainable temperatures.
Temperature Temperature Heat of Combustion Heat of Combustion
Fuel F C Btu/ft3 MJ/m3
Acetylene (C2H2) 5589 3087 1470 54.8
MAPP1 (C3H4) 5301 2927 5460 91.7
Hydrogen (H2) 4820 2660 325 12.1
Propylene (C3H6) 5250 2900 2400 89.4
Propane (C3H8) 4579 2526 2498 93.1
Natural Gas 4600 2538 1000 37.3
1) Methylacetylene propadiene
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Arc Welding
114
Arc Welding

• A fusion process wherein the coalescence of the
  metals is achieved from the heat of an electric
  arc formed between an electrode and the work.
• An electric arc is a discharge of electric
  current across a gap I a circuit.
• It is sustained by the presence of a thermally
  ionized column of gas (called a plasma).
• Temperatures up to 30,000C (54,000F) a
  generated

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Shielded Metal Arc Welding
116
Gas Metal Arc Welding
117
Gas Metal Arc Welding

• Originally called MIG welding (for metal inert
  gas)
• Used widely in factory fabrication
• Better metal usage (no stubs)
• Sticks or filler
• High deposition rates
• No slag

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Non-consumable Electrodes

• Gas Tungsten Arc Welding
• Known as TIG (tungsten inert gas) welding
• The electrode is W (tungsten)
• Tm 6170F (3410C)
• Actually it is slowly consumed
• Shielding gases include Ar, He or a mixture

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Gas Tungsten Arc Welding (TIG)
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Resistance welding
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Resistance Welding

• In order to obtain a strong bond in the weld
  nugget pressure is applied until the current is
  turned off.
• Strength depends on the initial surface condition
• Smoothness
• Cleanliness
• Presence of uniform thin oxides is not critical

122
Resistance Welding

• The reason that the current is so high is because
  the R is usually so low 0.0001 ohm

• Where
• I current (amperes)
• R resistance (ohms)
• T time of current (seconds)
• Q heat in Joules

123
Resistance welding

• Pay attention to the energy problem
• How much heat is used and how much is dissipated.
• Understand the current pressure cycle

124
Brazing and Soldering
125
Faying surfaces the surfaces to be joined.
Brazing

• A process which a filler metal is placed at or
  between the faying surfaces, the temperature is
  raised high enough to melt the filler metal but
  not the base metal.
• The molten metal fills the spaces by capillary
  attraction.
• Two types
• Ordinary brazing (above)
• Braze welding (similar to oxy-welding)

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Brazing Capabilities

• Typical joints
• Dissimilar metals can be assembled with good
  joint strength.
• Shear strength can reach 120 ksi (800 MPa) using
  alloys containing silver.
• Concerns
• Clearance too small, metal will not penetrate
• Clearance to big, insufficient capillary
  attraction.

127
Soldering
128
Soldering

• Used extensively in the electronics industry
• Soldering temperatures are low
• Not used in load bearing members
• Butt joints rarely made
• If strength is needed, the joint may be
  mechanically interlocked

129
Solder joints

• Typical joints
• Note that the starred examples are mechanically
  joined first.
• Copper and silver are easy
• Fe, Al hard to solder because of their tough
  oxide films.

130
Adhesive Joints
131
Adhesive Bonding

• Joining process whereby a filler material is used
  to hold two closely spaced parts together by
  surface attachment
• Filler material (adhesive)
• Usually non-metal
• Usually a polymer
• Curing
• Process (usually chemical) whereby the adhesive
  physical properties are changed from a liquid to
  a solid.

132
General Properties of some adhesives

• Acrylic
• Thermoplastic, quick setting, tough bond at r.t.
• Tennis racquets, metal parts
• Epoxy
• Thermoset, strongest engineering adhesive
• Metal, ceramic, rigid plastic parts

• Cyanoacrylate
• Thermoplastic, touch
• Crazy Glue
• Hot Melt
• Thermoplastic, quick setting, easy to apply
• Bonds most anything
• Packaging, book binding, metal can joints

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General Properties of some adhesives

• Phenolic
• Thermoset, strong, brittle
• Brake lining, clutch pads, honeycomb structures
• Silicone
• Thermoset, slow curing, flexible, rubber like
• Gaskets sealants

• Water base
• Animal
• Vegetable
• Rubbers
• Inexpensive, non-toxic
• Wood, paper, fabric
• Leather, dry seal envelopes

134
Joint Design

• Usually not as strong as welding or brazing
  joints
• Design principles
• Maximize joint contact area
• Joints are strongest in shear and or tension so
  joints should be designed to accommodate this
• Joints are weakest in cleavage or peel. Avoid
  these stresses

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Adhesive bonding Disadvantages

• Joints are not as strong
• Adhesive must be compatible with materials being
  joined
• Service temperatures are limited
• Cleanliness and surface preparation prior to
  adhesive application are important
• Curing times can impose a limit on production
  rates
• Inspection of the bonded joint is limited.