8. Compared to traditional materials (metals):
✓Disadvantages
✓(-) Greater materials cost and cycle time
✓(-) Less material characterization
✓(-) Less CAE/simulation tool development
✓(-) Lower service temperature
Composite Properties
BRIGHAM YOUNG UNIVERSITY8
9. • (+) Great engineering freedom
• (-) “Black aluminum”, wetting fibers
• (+) Light-weight
✓Save 10kg on A320
✓= 1974 L / year / plane
✓3404 planes
✓= 6,7M L / year
BRIGHAM YOUNG UNIVERSITY
Composite Properties
9
12. Composite Properties
•Compared to traditional materials (metals):
✓+Superior crash performance
HP Composites
Wichita State University
BRIGHAM YOUNG UNIVERSITY12
13. Composite Properties
•Compared to traditional materials (metals):
✓(+) Superior crash performance
BMW Megacity Bumper carrier
BRIGHAM YOUNG UNIVERSITY13
14. Composite Properties
•Compared to traditional materials (metals):
✓(+) Better dampening properties
ACPT auto driveshaft study
BRIGHAM YOUNG UNIVERSITY14
16. •Compared to traditional materials (metals):
✓Disadvantages
✓(-) Low ductility
✓(-) Damage susceptibility
✓(-) Hidden damage
✓Advantages
✓(+) Easily moldable
✓(+) Easily bondable / part consolidation
✓(+) Low electrical conductivity / high stealth
Composite Properties
BRIGHAM YOUNG UNIVERSITY16
17. Composites Categories
Advanced Thermoset Advanced Thermoplastics
Engineering Thermoset Engineering Thermoplastic
High temperature capabilities
High Cost
High strength
High modulus
Good fiber wet-out
Brittle
High cost
Solvent resistance
High toughness
Poor wet-out
High strength
Low cost
Excellent wet-out
Moderate strength
Brittle
Low cost
Standard TP mfg
Short fibers
Moderate strength
Good toughness
BRIGHAM YOUNG UNIVERSITY17
19. Resins
• Resin = matrix
• Some properties of the composite are dominated by the matrix
Property Cause
Resistance to solvents or water Polarity
Gas permeability Crystallinity
Fire resistance Aromaticity or halogen content
Thermal resistance Molecular weight, internal stiffness
Weather resistance Aliphatic content, additives and fillers
Toughness Aliphatic content, rubber tougheners
Wet-out of fibers Molecular entanglement (viscosity)
Electrical properties Polarity and filler content
BRIGHAM YOUNG UNIVERSITY19
22. • Increases in molecular weight (length of the polymer chain) result
in increases in most mechanical and thermal properties
✓Entanglement inhibits molecular motion
Resins
BRIGHAM YOUNG UNIVERSITY22
24. Increases in molecular weight (length of the polymer chain)
result in decreases in ease of processing
Low viscosity fluid
High viscosity fluid
Resins
BRIGHAM YOUNG UNIVERSITY24
25. The Great Dilemma in Polymers
• Polymers must have good
properties
✓Good properties are favored by
high molecular weight
• Polymers must have good
processing
✓Good processing is favored by
low molecular weight
Molecular Weight
MechanicalProperties
Molecular WeightEaseofProcessing
BRIGHAM YOUNG UNIVERSITY25
26. The Great Dilemma In Polymers
•Thermoplastics meet the dilemma by compromise
✓High enough molecular weight to get adequate properties
✓Low enough molecular weight to process OK
•Thermosets meet the dilemma by crosslinking
✓Low molecular weight initially (for wetout and processing)
followed by curing to increase molecular weight
✓No compromise is required
BRIGHAM YOUNG UNIVERSITY26
28. The presence of crosslinks dramatically changes
the viscosity, mechanical and thermal
properties of polymers
Crosslinking
BRIGHAM YOUNG UNIVERSITY28
29. Thermoplastics…
•Are not crosslinked and so they melt
•Are molded as molten liquids
•Are cooled to re-solidify
•Can be re-melted repeatedly
candy
BRIGHAM YOUNG UNIVERSITY29
30. Thermosets…
•Are crosslinked and do not melt
✓Crosslinking is sometimes called curing
•Are molded as room temperature liquids or
low-melting solids
•Are heated to solidify (harden)
•1-time only
cake
Coconut-filled cake
= a reinforced composite
BRIGHAM YOUNG UNIVERSITY30
37. • Largest group of thermosets
• Least expensive thermoset
• Easiest to cure resin
• Usually reinforced with fiberglass
Unsaturated Polyesters (UPE)
BRIGHAM YOUNG UNIVERSITY37
38. • Polymerization of unsaturated polyesters occurs
by a “condensation” reaction
✓Polyester = a polymer in which ester groups are the
repeating units formed in polymerization
✓Polyesters are made from two types of monomers:
•Di-acids
•Di-alcohols (“Glycols”)
Polyester Polymerization
BRIGHAM YOUNG UNIVERSITY38
40. Polyester Polymerization
One end of the di-acid (the OH group) reacts
with one end of the glycol (the H group) to
form water (H−OH)
The water separates from the polymer and condenses
out as a liquid (hence “condensation reaction”)
BRIGHAM YOUNG UNIVERSITY40
41. HO―G―OH
Glycol
OH C A C OH
O O
Di-acid
Step 1: Monomers react
+
Step 2: New molecule reacts with new monomers
O O
HO―G―O―C―A―C―OH + HO―G―OH
Glycol
OH C A C OH
O O
Di-acid
+
Ester Ester Ester
O O O O
HO―C―A―C―O―G―O―C―A―C―O―G―OH
HO―G―O―C―A―C―OH
OO
Ester
New bond
+ H2O
+ 2 H2O
Polyester Polymerization
BRIGHAM YOUNG UNIVERSITY
42. Building your perfect UPE
BRIGHAM YOUNG UNIVERSITY42
“Cooking recipe” - The types of di-acids and
glycols and their percentages determine the
properties of the unsaturated polyester.
Example: the amount of unsaturated monomer
controls the amount of crosslinking (crosslink density)
43. “Unsaturated” = contains carbon-carbon
double bonds after polymerization (but
before crosslinking)
Unsaturated Polyesters (UPE)
BRIGHAM YOUNG UNIVERSITY43
44. StructureName Comments
Fumaric acid
Maleic acid
Maleic anhydride
Trans isomer,
highly reactive,
crosslinkable
Cis isomer,
converts to fumaric acid,
crosslinkable
Readily converts to
maleic acid and
fumaric acid
in presence of water,
crosslinkable
Choice: unsaturated di-acid monomers
BRIGHAM YOUNG UNIVERSITY44
46. Aromatic
Contains benzene
rings
Aliphatic
Does not contain
benzene rings
Organic molecules are either:
aromatic or aliphatic
(Determines several key properties)
Building your perfect UPE
BRIGHAM YOUNG UNIVERSITY46
47. CC...C C...
C
C
C
C
C
C
C...OC
C
C
C
C
CC
C
C
C
C
C
C
OCC C
O
OH OH
OHOHOH
C
C
CC
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
....C C...
C.......C
a) Aromatic group (benzene) b) Polystyrene (pendant
aromatic)
c) Epoxy (aromatic backbone)
d) Phenolic (aromatic network)
CC...C C...
C
C
C
C
C
C
H
H
H
H
H
H
Aromatic molecules
CC...C C...
C
C
C
C
C
C
BRIGHAM YOUNG UNIVERSITY47
48. Aliphatic molecules
C C
C C
H
H
H H
H
H
H
C
H
H H
C C――
│
COOH
│
│ │
HOOC H
H
C
C C
C O
O
C
H
H
H
H
HH
HH
H
( )n
BRIGHAM YOUNG UNIVERSITY48
50. Halogen atoms (F, Cl, Br, I) add flame
retardancy
Smoke evolution increased halogens, but that
smoke smothers the flames
Building your perfect UPE
BRIGHAM YOUNG UNIVERSITY50
51. Halogenated polymers
)(
n
)( n
C
Cl
C...C C...
...C C C C...
F F
FF
C
C
C
C
C
C
Br
BrBr
C...
Br
OCCC
O
Polyvinyl chloride (PVC)
Polytetrafluoroethylene (PTFE)
Brominated Epoxy
BRIGHAM YOUNG UNIVERSITY51
54. COCCOCCCCOH
O O O
COCCCCOCCOC
O O O
C OH
Iso (meta)
Isophthalic Polyester
unsaturationunsaturation
CCOCCOOC
O
CCC
OH
O
C
C
C C
C
C
O
O
C
C C C O
O
C O
C
C
C
O C C
OH
C
Bisphenol A Fumaric Acid Polyester
(Crosslinking occurs at the carbon-carbon double bonds)
Acid Acid Acid
Acid AcidBPA BPA
Glycol Glycol
Glycol Glycol Glycol
Building your perfect UPE
BRIGHAM YOUNG UNIVERSITY54
Fumaric acid Fumaric acidIsopthalic Acid
Isopthalic Polyester
Bisphenol A Fumaric Polyester
-C-O-
55. UPE Crosslinking
•Unsaturated polyesters cure by “addition” / “free
radical” reaction
✓Started by an initiator molecule reacting with a carbon-
carbon double bond
✓Proceeds as a chain reaction
•Once started, it will keep going until stopped
•Doesn’t need more initiator
•Makes its own reactive sites
BRIGHAM YOUNG UNIVERSITY55
56. Initiators
•Initiators sometimes called catalysts.
•The most common initiators are peroxides.
✓Split into free radicals which react easily with the double
bonds.
✓Free radicals have unshared electrons.
I–I I + I
Peroxide Initiator Freeradical
Reaction can be heat or chemical induced
BRIGHAM YOUNG UNIVERSITY56
57. C C C
C
Unsaturated bonds
Polyesters must have unsaturated portions to crosslink
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY57
60. C C C
CI
●
Bond (2 electrons)
Unshared electron or
free radical (reacts readily)
Formation of a bond and a new free radical
The new free radical needs to encounter (collide with) a double
bond on another polymer chain
Long and entangled (highly viscous), the chances of lining up are
not good
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY60
61. •Dissolve (dilute) the polymer in a solvent
✓Ideally, the solvent will react during crosslinking
•Called “reactive solvents” or “reactive diluents” or “co-reactants”
•Styrene (most common diluent)
•Added benefit: The solvent will also reduce the
viscosity; resin wets the fibers better
C
C
C
C
C
C
C C
or
UPE Crosslinking (Solution)
BRIGHAM YOUNG UNIVERSITY61
62. C C C
CI
●
Bond (2 electrons)
Styrene molecule
is attacked at
non-ring double bond site
C
C
C
C
C
C
C C
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY62
63. C C C
CI
Bond (2 electrons)
Formation of a new bond
and a new free radical
C
C
C
C
C
C
C C
●
Can link to another unsaturation site
(usually on another styrene molecule or another polymer)
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY63
64. C C C
CI
Styrene
C C C
C
New free radical
●
New bonds
(crosslink)
The new free radical is available to react with another double bond
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY64
65. • The addition reaction continues until one of the following
conditions is met:
✓Nothing more to bond with
•Reactive diluent (styrene) is not available
•Stops encountering other polymers’ double bonds
– Post-curing can improve crosslinking
✓The free radical site meets another free radical site on another polymer
✓The free radical site meets another initiator free radical
•Danger of adding too much initiator
✓The free radical reacts with a terminator molecule
•Ozone
UPE Crosslinking
BRIGHAM YOUNG UNIVERSITY65
66. Inhibitors
…Added to increase storage time, usually by
the resin manufacturer
Inhibitors typically absorb free radicals,
protects from sunlight, heat, contaminants, etc.
To cure, must add sufficient initiator to
overcome the inhibitors
BRIGHAM YOUNG UNIVERSITY66
67. Promotors (accelerators)
•Added to polymer to make the initiator work more
efficiently or at a lower temperature
✓Each peroxide has a temperature at which it will break
apart into free radicals, it’s usually above room temperature
✓For room temperature curing, a chemical method for
breaking apart peroxides is needed
•Most common = cobalt compounds and analines
(DMA)
•Never add a promoter directly into an initiator
BRIGHAM YOUNG UNIVERSITY67
68. Additives
•Components with various functions not
related to curing
✓Fillers (to lower cost and/or give stiffness)
✓Thixotropes (to control viscosity)
✓Pigments
✓Fire retardants
✓Surfactants (to promote surface wetting)
✓UV inhibitors/Anti-oxidants
BRIGHAM YOUNG UNIVERSITY68
71. Epoxies
•Second most widely used family of
thermosets (after polyesters)
•Large portion of uses are non-reinforced
(adhesives, paints, etc.)
•Circuit boards = largest reinforced
application (low conductivity, low
volatiles)
•Advanced composites use epoxies
because of:
✓Thermal stability
✓Adhesion
✓Mechanical properties
BRIGHAM YOUNG UNIVERSITY71
72. H―C―C―R
│ │
H H
O
H―C―C―C―R
│ │
H H
O
│
H
│
H
a) Epoxy group
b) Glycidyl group
“R” = Any organic chemical group
Epoxies
BRIGHAM YOUNG UNIVERSITY72
73. C
C
Epoxy ring – where crosslinking occurs
O
C
C
O
( )n
Polymer portion
Number of repeat units
Epoxies
BRIGHAM YOUNG UNIVERSITY73
75. Epoxy Properties − chain length (n)
Number of repeat
units (n)
Heat Distortion Temperature
(HDT) (°F/°C)
Physical state
2 105/40 Semi-solid
4 160/70 Solid
9 265/130 Solid
12 300/150 Solid
BRIGHAM YOUNG UNIVERSITY75
76. Epoxies
The number of epoxy groups determines the
amount of crosslinking.
Epoxy groups are at the ends of a chain, but the
molecule can have more than just 2 ends (“higher
functionality”).
This makes higher crosslinking density, gives thermal
stability but requires high curing temperatures
BRIGHAM YOUNG UNIVERSITY76
80. Flexibilized Epoxy
O
O
CCOCCOCCC
OH
C O C C C
OH
O C C O C C C
OH
N
C
C
C
NH2
C C C
OH
O C C O C C C
O
Flexibility allows motion and that absorbs energy (bullet-proof vest effect)
BRIGHAM YOUNG UNIVERSITY80
81. Epoxy curing
BRIGHAM YOUNG UNIVERSITY81
•Epoxies use hardeners instead of initiators for
curing.
✓Hardeners = react with (open) the epoxy ring
✓Hardeners have active groups at both ends
82. BRIGHAM YOUNG UNIVERSITY
Epoxy Crosslinking
C C
Epoxy ring
O
C
O
(
)n
Epoxy ring
N
N
H
H
HH
N
N
H
H
HH
C
Hardener molecules have two
reactive ends, so they can each
react with two epoxy molecules.
82
83. H
HN
C
C...
C
O
C C...
N
C
C...
C C C...
O
C C
H H
Hardener
Epoxy
The other ends can also react (usually with other epoxy molecules).
Cured Polymer
H
~
~
Epoxy Crosslinking
BRIGHAM YOUNG UNIVERSITY83
84. Building your perfect Epoxy
•Many different hardeners are available to cure
epoxies.
✓Very active ends on the hardener molecule allow
crosslinking at lower temperatures
•Hydrogens attached to highly electronegative atoms are
very active
•Nearby aromatic groups decrease activity, but increase
mechanical and thermal properties
•Nearby large groups of atoms hinder access and
therefore decrease activity (but increase stiffness)
BRIGHAM YOUNG UNIVERSITY84
85. BRIGHAM YOUNG UNIVERSITY
Choice: hardener
Hardeners Advantages Disadvantages
Aliphatic amines Convenience, low cost, room
temp cure, low viscosity
Skin irritant, critical mix
ratios, blushes
Aromatic amines Moderate heat resistance,
chemical resistance
Solids at room temp, long
and elevated cures
Polyamides Room temp cure, flexibility,
toughness, low toxicity
High cost, high viscosity,
low HDT
Amidoamines Toughness Poor HDT
Dicyandiamide Good HDT, good electrical Long, elevated cures
Anhydrides Heat and chem resistance Long, elevated cures
Polysulfide Moisture insensitive, quick set Odor, poor HDT
Catalytic Long pot life, high HDT Long, elevated cures,
poor moisture
Melamine/form. Hardness, flexibility Elevated temp cure
Urea/form. Adhesion, stability, color Elevated temp cure
Phenol/form. HDT, chem resistance, hardness Solid, weatherability
86. BRIGHAM YOUNG UNIVERSITY
Epoxy and Polyester Comparison
Comparisons Polyester Epoxy
Active site C=C
Crosslinking reaction Addition/free radical Ring opening
Crosslinking agent Initiator (peroxide) Hardener
Amount of x-link agent 1-2% of resin 1:1 with resin
Solvent/viscosity Styrene (active)/low Infrequent/high
Volatiles High Low
Inhibitors, accelerators Frequent Infrequent
Reactant toxicity Low Moderate
Cure conditions Room temp or heated Heated (some room)
Shrinkage High Low
Post cure Rare Common
O
C C
87. Property Polyester Epoxy
Adhesion Good Excellent
Shear strength Good Excellent
Fatigue resistance Moderate Excellent
Strength/stiffness Good Excellent
Creep resistance Moderate Moderate to good
Toughness Poor Poor to good
Thermal stability Moderate Good
Electrical resistance Moderate Excellent
Water absorption resist Poor to moderate Moderate
Solvent resistance Poor to moderate Good
UV resistance Poor to moderate Poor to moderate
Flammability resistance Poor to moderate Poor to moderate
Smoke Moderately dense Moderately dense
Cost Low Moderate
Epoxy and Polyester Comparison
BRIGHAM YOUNG UNIVERSITY87
89. Vinyl Esters
•Epoxy resins that have been modified so that they can
be cured like a polyester
✓The modification is usually a reaction with an acrylic (acrylic
modified epoxy)
✓The modification must substitute a carbon-carbon double
bond for the epoxy ring
BRIGHAM YOUNG UNIVERSITY89
92. •Almost all properties of vinyl esters (and cost) are
intermediate between polyesters and epoxies
✓Water and chemical resistance
✓Electrical stability
✓Thermal stability
✓Toughness
✓Low volatiles during manufacture
✓Low shrinkage
Vinyl Esters
BRIGHAM YOUNG UNIVERSITY92
94. •Both polymerizing and crosslinking
reactions occur simultaneously
✓The reactions can be stopped before completion to
still allow molding, but easier handling of the polymer
✓The resultant intermediate material is called the B-
stage and the processing is called B-staging.
Phenolics
BRIGHAM YOUNG UNIVERSITY94
96. BRIGHAM YOUNG UNIVERSITY
Problem Solution
Toxic monomer
(formaldehyde)
B-staging to novolac (solid)
or resole (liquid)
Condensation of water Slow cures and venting of
mold
High shrinkage Fillers (minerals, sawdust,
wood flour, ground nut
shells, etc.)
Brittleness Fillers (selected) and
thickness of parts
Inconsistent color Black pigment
Phenolics
96
98. Phenolics
• Highly Aromatic
- Very low flammability and low smoke
- Very stiff and hard
- Very low heat transfer
- High thermal stability
- Good electrical properties
- Moderately low price (10-15% above polyesters)
BRIGHAM YOUNG UNIVERSITY98
99. Phenolics
•Applications
✓Interiors of public transportation
✓Glue for laminates (such as plywood)
✓Electrical switches and other equipment
✓Molded parts in moderately hot environments (e.g.
near the motor of an automobile)
✓Rocket exit nozzles and carbon-carbon composites
(ablation)
BRIGHAM YOUNG UNIVERSITY99
100. 10 20 30 40
Vinyl Ester
Epoxy
FR Polyester
Phenolic
(ASTM E-162 for thermoset
composites)
Vinyl Ester
Epoxy
FR Polyester
Phenolic
(ASTM E-662 for thermoset
composites)
100
Specific Optical DensityFlame Spread Index
200 300 400 500 600
Phenolics
BRIGHAM YOUNG UNIVERSITY100
101. 106-
105-
104-
103-
102-
10-
1-
0 1000 2000 3000 4000
-18 538 1093 1650 2204
Temperature
oF
oC
Exposure
Time
(sec)
EpoxyComposites
Polyimides
Advanced
Metalics
Carbon-Carbon
Experimental
Ablative Materials
(such as phenolics)
Mechanical Endurance at high T
BRIGHAM YOUNG UNIVERSITY101
102. Rocket Exit ThroatExit Nozzle
(Ablative
Material)
10 oF
500 oF
4000 oF
Rocket
Motor
Rocket
Propellant
Nose
Cone
Phenolics in Ablation
BRIGHAM YOUNG UNIVERSITY102
103. • Aromaticity comes from cyclical groups
other than benzene
✓These rings give even higher thermal stability.
✓Very difficult to process.
✓Usually also contain many benzene rings, too.
• Example: Bismaleimide (BMI)
CC C
C
N
C
O
O
CC
C
N
C
O
O
Crosslink sites
Polyimides
BRIGHAM YOUNG UNIVERSITY103
www.sldinfo.com
106. Composites Categories
Advanced Thermoset Advanced Thermoplastics
Engineering Thermoset Engineering Thermoplastic
High temperature capabilities
High Cost
High strength
High modulus
Good fiber wet-out
Brittle
High cost
Solvent resistance
High toughness
Poor wet-out
High strength
Low cost
Excellent wet-out
Moderate strength
Brittle
Low cost
Standard TP mfg
Short fibers
Moderate strength
Good toughness
BRIGHAM YOUNG UNIVERSITY106
112. SOC( )nO
CH3
CH3
O
O
SSS( )n
a) Polysulfone (PSU)
b) Polyphenylene sulfide (PES)
Sulphur-containing advanced thermoplastics
BRIGHAM YOUNG UNIVERSITY112
www.mprplastics.com
115. Thermoplastic − Advantages
•Toughness
•Solvent resistance
•Re-molding
•Processing by conventional thermoplastic
method (engineering thermoplastics with very
short fibers)
•Processing times (cool versus cure)
•Shelf life
BRIGHAM YOUNG UNIVERSITY115
119. •Some properties of the composite are dominated
by the reinforcement
✓Reinforcements are anisotropic materials
✓Reinforcements typically carry over 90% of the load
✓Longer fibers can carry more load
Reinforcements
BRIGHAM YOUNG UNIVERSITY119
127. Property Type of fiberglass
E-Glass S-Glass C-Glass
Coefficient of thermal expansion (10-6 ˚C) 5.2 5.7 7.3
Specific heat (kJ/kg ˚C) .810 .737 .787
Softening point (˚C) 846 970 750
Dielectric strength (kV/cm) 103 130 –
Index of refraction 1.562 1.525 1.532
Weight gain after 24h in water (%) 0.7 0.5 1.1
Weight gain after 24h in 10% HCl (%) 4.2 3.8 4.1
Weight gain after 24h in 10% H2SO4 (%) 3.9 4.1 2.2
Fiberglass – Grades
BRIGHAM YOUNG UNIVERSITY127
128. •Stiffest of the common fibers
•Generally the best specific strength and specific stiffness
Carbon
Car and Driver
BRIGHAM YOUNG UNIVERSITY128
134. •Material changes from PAN fibers to carbon
fibers:
✓Diameter cut in half
✓Tensile strength / modulus increase by 20x
✓Elongation-to-failure drop from 4.8 to 1.6%
✓Resistivity drop from 454 to .0008 ohm-in
✓Cost increase from $3.88 to $8.30 per pound
•Carbon vs. graphite
Carbon – Production
BRIGHAM YOUNG UNIVERSITY134
136. Carbon Fibers
•Applications
✓Based on strength, stiffness, and low weight
✓Based on thermal properties
✓Based on chemical inertness
✓Based on rigidity and good damping
✓Based on electrical properties
✓Based on biological inertness and x-ray permeability
✓Based on fatigue resistance and self-lubrication
BRIGHAM YOUNG UNIVERSITY136
141. • Ballistic Protection
✓Stop the bullet
✓Spread the energy
Threat Level Number of
Layers
Ammunition
Stopped
2A 22 9mm
2 32 44 magnum,
357 magnum
3A 40 Wad cutter,
240 grain
bullet
Aramid (and UHMWPE)
BRIGHAM YOUNG UNIVERSITY141
142. Fiber-Matrix Interactions
•Wetting / bonding of matrix on fibers
•Sizings / Finishes
✓Protect the brittle fibers from mechanical damage
✓Enhance the bonding of the fibers to the matrix
•Polyester and fiberglass
BRIGHAM YOUNG UNIVERSITY142
143. Fiberglass
Sizing or coupling agent
...O Si O Si O...
OH
OH
OH
OH
....C C O C C C
O
C C...
CH3 Si O C C C
CH3
C C C C...
CH3 Nonpolar regions (weak attraction)
d-
d-
d+
d+
d+ − A highly polar molecule
− Largely non-polar with a polar endPolyester
− Mixed polar/non-polar
Polar
regions
attract
Non-polar
Fiber-Matrix Interactions
BRIGHAM YOUNG UNIVERSITY143
144. Common failure modes for polymeric matrix
composites
Fiber-Matrix Interactions
BRIGHAM YOUNG UNIVERSITY144
145. • Measurement of Fiber-Matrix Bond Strength
✓Bias tensile / Short Beam Shear / Inter-Laminar Shear
Force
Composite sample that is
too thick and short to bend
Supports
Fiber-Matrix Interactions
Northwestern U.
BRIGHAM YOUNG UNIVERSITY145
151. Sandwich / Cores
•Stiffness is proportional to thickness
✓Add thickness without adding weight
Jungbluth, “Verbund- und Sandwichtragwerke” Springer-Verlag 1986
BRIGHAM YOUNG UNIVERSITY151
