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Konstruktion i polymera kompositmaterial > Inför tentan > Flashcards

Inför tentan Flashcards

1
Q

What does CFRP consist of?

A

Carbon fiber reinforced plastics. Carbon fibers and plastics.

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2
Q

Name three advantages with PMC.

A

Specific stiffness

Specific strength

Light weighted

Corrosion resistance

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3
Q

Name three disadvantages with PMC.

A

Temperature range

Long manufacturing time

Expensive

Recyclability

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4
Q

Why is it easier to manufacture thermoset-based composites than thermoplastic-based composites?

A

No need to melt anything. Lower viscosity, easier to impregnate the fibers

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5
Q

Name the three most common types of fibers in PMC.

A

Carbon, Aramid, Glass

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6
Q

Name two advantages with carbon fiber.

A

Very strong

Very stiff

Thermal and electrical conductivity

Excellent fatigue properties

low thermal expansion

good X-ray permeability

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7
Q

Name two disadvantages with carbon fiber

A

Expensive

Low failure strain / brittle

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8
Q

What does the abbreviation “IM” means regarding carbon fibers

A

Intermediate modulus

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9
Q

Name two advantages with glass fiber.

A

High strength

Good thermal properties

Good corrosion resistance

Good thermal and electrical insulation

Low price

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10
Q

Name two disadvantages with glass fiber.

A

Low stiffness

Sensitive to moisture

Sensitive to notches

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11
Q

What is the difference between S-glass fibers and E-glass fibers?

A

S-glass more expensive

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12
Q

Describe E-glass

A

E-glass: Electrical Grade, most common type (99% of all continuous fibers)

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13
Q

Describe S-glass

A

S-glass: High strength grade, 30% higher strength and 20% higher stiffness than E-glass. More expensive

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14
Q

Name three common types of natural fibers.

A

Hemp, flax, cotton, ramie, jute, coconut, wood

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15
Q

What does NCF mean?

A

Non crimp fabric

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16
Q

Describe the structure of NCF.

A

Fabric that doesn’t crimp. Better compression properties? Unidirectional layers/ CSM are stitched together to prevent movement with polyester
Higher stiffness and strength compared to weaves

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17
Q

Name the three most common types of thermosets in PMC.

A

Epoxi, Polyester, Vinylester

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18
Q

Name two advantages with epoxy

A

Mechanical properties

Thermal resistance

Chemical resistance

Electrical insulation

Excellent adhesion

Low shrinkage at cure

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19
Q

Name two disadvantages with epoxy

A

Allergic reactions

Toxicity

Poor UV resistance

Expensive

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20
Q

What is important to remember when you work with epoxy?

A

Gloves and ventilation.

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21
Q

Name two advantages with UP.

A

Unsaturated polyester

Good mechanical properties

Low viscosity

Easy curing

Low price

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22
Q

Name two disadvantages with UP.

A

Low temperature resistance

Large shrinkage at cure

Problem with styrene evaporation. Good ventilation necessary!

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23
Q

Why are glass fibers covered by sizing?

A

To improve (chemical) adhesion to the matrix.

Protect the fibers.

Avoid static electricity.

Keeping the fibers in bundles.

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24
Q

Why is it normally good with a strong bonding between the fibers and the matrix?

A

Evenly disperse the force.

Preventing debonding / delamination

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25
Q

Why is it not so wise to use old glass fibers?

A

The sizing dries with time –> poor bonding

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26
Q

Why are residual stresses formed in PMC?

A

Different thermal expansion coefficients

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27
Q

Name two advantages with biocomposites.

A

Renewable resources

Easy to market

Low price

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28
Q

Name two disadvantages with biocomposites.

A

Moisture sensitive

Variances in the fibers due to different growth

Relatively low strength

Long-term properties

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29
Q

Name two common nano-reinforcements in composite materials.

A

Carbon nanotubes

Nanoclay

Cellulose fibrills

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30
Q

Why does unsaturated polyester normally contain styrene?

A

To lower the viscosity (30-35%)

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31
Q

How is curing of unsaturated polyester initiated?

A

Adding a free radical catalyst –> start the chain reaction of polymerization

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32
Q

What’s the purpose of adding inhibitors?

A

To prolong the working time. Control the curing.

Only prolongs the reaction ~ 2 hours → need more time? change catalyst! the inhibitor can affect the properties

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33
Q

Which resins do often contain an inhibitor?

A

polyester resins

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34
Q

What’s the purpose of adding accelerators?

A

Speeding up the curing process.

green/bluish due to cobalt

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35
Q

Why should accelerators and catalyst never be mixed directly together?

A

they can burn/explode

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36
Q

If you want to add both accelerator and catalyst what should you do?

A

1)add the accelerator 2) stir & dissolve 3) add the catalyst

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37
Q

What is the “pot-life”?

A

The time until curing starts

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38
Q

How does the temperature affect the pot-life?

A

Increase temperature → more rapid curing process → shorter pot-life

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39
Q

How does vitrification affect the curing?

A

It abruptly halts the curing (if you want further curing → heat it up to the rubbery phase)

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40
Q

Name five parameters that affect the pot-life and curing of vinyl esters

A

Catalyst used

Accelerator used

Inhibitor used

Temperature

Age of resin

Mass to be cured

Applied heat

Size and type of mould

Fillers/reinforcements

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41
Q

What is gelation?

A

Gelation is characteristic for thermosets, and it is of foremost significance

From a processing standpoint, gelation is critical since the polymer does
not flow and is no longer processable beyond this point.

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42
Q

What is Vitrification?

A

glassy states –> abrupt halt to curing

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43
Q

Describe the curing of epoxy.

A
  1. starts with connecting monomers in a liquid state.
  2. Reaches gelation (does not affect the movement of monomers)
  3. Reaches vitrification (glassy state)

To cure an epoxy resin a hardener is needed.

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44
Q

What temperature is required when curing epoxy?

A

Some epoxy systems can be cured even at temperatures as low as 0°C. However, to obtain good mechanical properties it is normally recommended to cure the resin at +20°C and then (if needed) post cure the material at higher temperature.

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45
Q

When curing epoxy, a hardener is required. What does this affect?

A

Different harderners have different ideal curing temperatures → affects the curing rate.

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46
Q

How is the temperature of curing epoxy determined?

A

The higher the temperature is of curing epoxy, the faster it cures. The temperature of curing epoxy is determined by the ambient temperature plus the exothermic heat generated by its cure. (ambient temperature + exothermic heat)

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47
Q

What happens when heating epoxy that has not gelled?

A

will lower its viscosity, allowing the epoxy to run or sag more easily on vertical surfaces.

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48
Q

What can happen when heating epoxy applied to a porous substrate?

A

heating epoxy applied to a porous substrate (softwood or low-density core material) may cause the substrate to “out-gas” and form bubbles in the epoxy coating. To avoid out-gassing, wait until the epoxy coating has gelled before warming it.

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49
Q

How does incomplete curing effect epoxy?

A

 Lower stiffness
 Higher moisture absorption
 Reduced chemical resistance

Risk of allergic reaction

Skin, red and swallowed

Stiffness not as high as expected, higher moisture, bad chemical resistance

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50
Q

Name three important substances to look out for when working with thermoset-based composite materials.

A

Styrene, epoxy, dust, solvents (catalysts, accelerators)

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51
Q

What is important to remember when working with uncured epoxy?

A

Use suitable gloves!

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52
Q

What is important to remember when working with uncured polyester?

A

Good ventilation!

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53
Q

How can the amount of styrene in the air be reduced when working with UP?

A

Add some wax? Places on the top of the material ⇒ reduce the styrene in the air

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54
Q

How can the curing of thermosets be studied?

A 
 Spectroscopy
 Magnetic resonans (NMR)
 Thermal analysis (DSC)
 Dielectric measurements
 Hardness tests
 Tensile tes
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55
Q

How can the amount of styrene in the air be reduced when working with UP?

A

Add some wax? Places on the top of the material ⇒ reduce the styrene in the air

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56
Q

How shall waste and spill of uncured resins be taken care of?

A

Place it in bags
Mark the bags with thermosets
Clean floor etc.

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57
Q

Describe the manufacturing of a plug

A

In order to make a mould, we make a plug = master model
Wood, plywood, cover it with clay, mill it in order to get the right dimensions, finish and polish surfaces. Paint the plug and add wax to the plug in order to not get stuck

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58
Q

Describe the manufacturing of a mould when you have a plug.

A
  1. Apply a gelcoat
  2. Apply laminate layer of glass fibre (CSM) + temperature resistant esin
  3. Apply structural laminate layer (in steps to avoid shrinkage) CSM or spray- up of glass fiber and polyester
  4. Add stiffeners: built up by fibre-reinforced plastics
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59
Q

Describe a good way of de-moulding a composite motorboat hull

A

Start the de-moulding process by trimming the edges.
Then release the edges by the use of wooden or plastic wedges.
Apply compressed air carefully along the released edges.
Remove the component!
Store the component appropriately until it has fully cured

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60
Q

What different manufacturing methods are Fosieplast using?

A

Hand lay-up (poor mechanical properties) and Vacuum Injection Moulding (large components)

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61
Q

Name 5 advantages with vacuum injection moulding compared to hand lay-up

A 
better mechanical properties (less voids)
better working environment
faster process
less material needed (spill)
cheaper
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62
Q

Why are different types of flow media used in vacuum injection moulding

A

to be able to impregnate a long piece

to speed the process up for large components

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63
Q

Describe the structure for three different types of flow media

A

 Surface medium
allows very fast distribution of large quantities of resin,
and provides good control over the flow front
 Core channels
most effective on flat surfaces,
and a very effective, waste-free way to infuse parts

 Interlaminar medium

highly porous
layer in the laminate, such as a continuous roving material or a nonwoven
breeder-like material

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64
Q

What is a “skin coat”?

A

Normally, a skin coat consists of a few layers of CSM with a high quality, low-shrink resin.
flat shiny surface (not fibers), made from hand lay-up → prevent fiber print-through

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65
Q

What is a barrier coat?

A

similar… but made out of a resin layer.

more effective than skin coat

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66
Q

What different types of manufacturing methods are “Composite Design” using?

A

prepreg (low voids, high fibres)

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67
Q

Pros with prepreg?

A

high fibre content

low void content → good mech. properties

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68
Q

Cons with prepreg?

A

touch when not cured: allergic reactions

expensive

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69
Q

Describe the different steps in prepreg lay-up

A
  1. need a mould
  2. apply a release agent (to be able to remove it later on)
  3. take out the material from the freezer (prevents it from curing)
  4. cut number of samples of prepreg
  5. place the samples in the mould (apply only a few layers)
  6. debulking: apply vacuum bag to remove embedded air
  7. add more layers …etc…
  8. bleeder put it in an autoclave (to cure it)→ press out the air (can tolerate <1% =good quality)
  9. remove from autoclave → trim it
  10. Post work
70
Q

What does it mean when a prepreg material is “Non-bleed”

A

would like as much fibre as possible and as little epoxy as possible

the bleeder takes up the extra amount of epoxy

when we don’t have any extra epoxy in the material, we don’t need the bleeder → non-bleed

71
Q

What is meant by out-of-autoclave technique?

A

autoclave is very expensive
manufacture it without the autoclave
Use other methods such as RTM or vacuum + oven
not as good properties but much cheaper!

72
Q

How high amount of fibres can be obtained in a prepreg laminate?

A

65-75%

73
Q

What is the theoretical maximum amount of fibre in a laminate?

A

90-91% due to the placement

74
Q

Describe the different steps in RTM.

A
  1. Dry fibers in mould
  2. Press the fibers in the mould to shape
  3. Inject the resin
  4. Let cure

Nice surfaces

75
Q

What is the difference between HP RTM and LP RTM?

A

HIgh/low pressure

High: good tolerances, more expensive

76
Q

What type of property is described by the permeability?

A

easy for the resin to flow and impregnate

how easy it is to flow through a porous media

77
Q

What does “race-tracking” mean?

A

flows easier in the edges → in the middle we get dry spots

78
Q

What does does SMC sheet moulding compound consist of?

A

chalk
glass fibers
unsaturated polyester

79
Q

What does does AMC advanced moulding compound consist of?

A

similar as for SMC

remove the chalk
epoxy
carbon fibers
fast cycle time
lower density
80
Q

Describe how wet moulding works

A

1) make mould place dry fibers
2) spray the fibers with resin
3) close the mould→ wet out the fibers

81
Q

Name 3 typical applications for filament winding

A

pressure vessels
pipes
masts

82
Q

Describe the difference between pultrusion and extrusion

A

Pull fibers through the die
slow process (not cost efficient)
better insulation by pultrusioned composites

83
Q

What is GMT?

A

Glass mat thermoplastics

84
Q

How does Composite laminate with UD fibers in the loading direction fail in compression?

A

Fiber micro-buckling (the fibers will buckle) → formation of kink band
Happens quite early. Compression strength is ALWAYS lower than tensile strength

85
Q

Which is the first damage mechanisms in tensile loading of a cross- ply laminate?

A

matrix/transverse cracking
controlled by ductility, sizing
(0.4% strain)

86
Q

Why are overloads more detrimental for composite materials than for metals?

A

Can lead to matrix cracking → will grow → cause delamination

87
Q

Name 5 parameters that influences the size of an impact damage

A

geometry of the impactor

amount of fibers

sizing

reinforcement in Z direction

ductility of matrix

thickness of laminate

speed of impact

88
Q

What different types of damages can appear when a composite component is hit by an object?

A
  1. matrix cracking
    • delamination
    • fiber failure/fracture
89
Q

How can the impact tolerance of a composite component be improved?

A

good adhesion between fiber/matrix
possibility to move and doesn’t need to take up all the energy
reinforcement in Z direction
placement of fibers

90
Q

What is the biggest problem with composites?

A

impact!!

91
Q

Why is it interesting to test the shear properties of composite materials?

A

lammellaes will like to slide → delamination
have to restrict this with high shear strength
need high shear strength between the lamellas

92
Q

Why is it not good to combine aluminium and carbon fiber- reinforced plastics?

A

galvanic corrosion → aluminum will disappear

apply thin layer of glass fiber to prevent contact between carbon fiber and aluminum

93
Q

What different types of defects can appear during secondary processing?

A

delaminations will form on the back side when drilling a hole

microcracks in resin

matrix crack

reorient the fibers

debonding between the fiber/matrix

94
Q

Name 2 pros with water jet cutting of composite laminates

A

no HAZ

fast

nice cuts

no big health concerns

can add sand to be able to get through thicker plates

95
Q

Name 2 cons with water jet cutting of composite laminates

A

some materials are sensitive to water → fibers can rotten

costly technique

96
Q

Why is strain, and not the stress plotted on the y-axis in fatigue diagrams for composite laminates?

A

stress varies for different directions, and for fiber/matrix

97
Q

Why is it not good if fibers shift and move during manufacturing?

A

huge reduce of stiffness and strength for just a small angle difference

98
Q

Which is the minimum acceptable radius in composite components?

A

5 mm, but rather 10

otherwise resin rich area

99
Q

Why are residual stresses formed in fiber-reinforced plastics?

A

matrix and fiber will not have the same shrinkage

fiber less than matrix

both chemical and thermal shrinkage
chemical → curing

Absorption of moisture

can lead to warpage/cracking

100
Q

Why is it important with low out-of plane stresses in composite materials?

A

poor properties of matrix compared to fibers.

if this direction is loaded → delaminations & failures

101
Q

Why is the design/strain limit often as low as 0.3% for composite components in the aircraft industry?

A

0.5- 0.6 % matrix cracking ( is not allowed, stay below)
static loading
fatigue loading, matrix cracking can occur earlier than 0.5%
stay below fatigue limit

102
Q

How is a symmetric lay-up created?

A

90-45-45-90 (symmetric according to the mid-plane)
shrinks the same at the top/bottom
avoid warpage (same residual stresses at top and bottom)

103
Q

Why is a symmetric lay-up favorable?

A 
shrinks the same at the top/bottom
avoid warpage (same residual stresses at top and bottom)
104
Q

How much does glass fiber approximately cost per kilo?

A

25 kr/kg

105
Q

How much does carbon fiber approximately cost per kilo?

A

> 150 kr/kg

106
Q

How much does carbon fiber prepreg approximately cost per square meter?

A

250-275 kr/m2 (200 g/m2 weave)

107
Q

Suggest a suitable material for a component which shall be stiff and cheap.

A

Steel, aluminum, plywood

108
Q

What does E2 describe in laminate theory?

A

Transverse stiffness (Young’s modulus)

109
Q

How can the stiffness in the fiber direction for a UD laminate be calculated?

A

E = E1V1 + E2V2

110
Q

Explain how the weight fraction fiber can be changed to volume fraction.

A

Use the density

111
Q

How shall the fibers in a laminate be placed to obtain the maximum bending
stiffness?

A

Along the bend [0 degrees]

112
Q

What does the [A] matrix in laminate theory describe?

A

Extensional stiffness matrix - This matrix influences extensional strains in the laminate

113
Q

What does the [B] matrix in laminate theory describe?

A

Bending-extension coupling matrix - This matrix couples extensional response to the bending response in the laminate

114
Q

What does the [D] matrix in laminate theory describe?

A

Bending stiffness matrix - This matrix influences the bending response in the laminate

115
Q

Describe the stacking of a symmetric laminate.

A 
90
0
-45
------------
-45
0
90
116
Q

Why is it normally good with symmetric laminates?

A

Decreases warping, residual stresses

117
Q

Why do the strains in a laminate vary linearly through the thickness while the
stresses do not?

A

The stresses in a laminate varies from layer to layer

118
Q

What is the stiffness transverse to the fiber direction (E2)?

A

E2 = Ef * Em / (Vf Em + Vm Ef)

119
Q

WHat are the 3 ways of applying a force to make a crack propagate?

A

Mode I fracture
Mode II fracture
Mode III fracture

120
Q

Explain Mode I fracture

A

Opening mode (a tensile stress normal to the plane of the crack)

121
Q

Explain Mode II fracture

A

– Sliding mode (a shear stress acting parallel to the plane of the crack and perpendicular to the crack front)

122
Q

Explain Mode III fracture

A

– Tearing mode (a shear stress acting parallel to the plane of the crack and parallel to the crack front)

123
Q

What is Gc?

A

the fracture energy

124
Q

What does the quantity Gc describe?

A

The energy release rate failure criterion states that a crack will grow when the available energy release rate G is greater than or equal to a critical value Gc

125
Q

How is G1c normally measured for composite laminates?

A

Double cantilever beam test

pull laminates apart

126
Q

How is G2c normally measured for composite laminates?

A

End notch flexural test

127
Q

How is End notch flexural test performed?

A

put a laminate on two holders, push down the middle part, the laminates will shear on each other

128
Q

What does the effectiveness of toughening mechanisms in composite materials depend on?

A

Size, morphology and volume fraction of the reinforcement

Interfacial bond strength

Properties of the fibers and matrix (e.g. thermal expansion)

129
Q

Name 3 toughening mechanisms

A
  1. Fibre bridging
  2. Microcracking
  3. Crack deflection
  4. Debonding (The process of fiber debonding creates new surfaces in the composite material
    and therefore requires energy)
130
Q

Describe how energy is consumed by fiber pull-out.

A

W = force* distance

the force needed to overcome is due to friction.

if length of fiber > critical length –> the fiber will break instead

131
Q

How long are the fibers normally in “long fiber thermoplastics” before injection
moulding?

A

(12.5-25 mm) As long as the pellets used

132
Q

How long are the fibers normally in “long fiber thermoplastics” after injection
moulding?

A

4-6 mm

133
Q

How long is the “critical” fiber length for GFRP normally?

A

normall around 2mm?

134
Q

How does the fiber length affect the mechanical properties of short fiber
composites?

A

Longer fibers = better properties

critical length to be able to transfer the load and use the fiber

135
Q

How does the fiber/matrix bonding affect the mechanical properties of short fiber
composites?

A

Better bonding results in better mechanical properties

136
Q

What can be calculated by the Halpin-Tsai equations?

A

Halpin- Tsai : calculate stiffness of short fiber, aligned

137
Q

Name two advantages with natural fibers compared to

glass fibers.

A

Cheaper (?)

Environmentally friendly

138
Q

Name two disadvantages with natural fibers compared to

glass fibers.

A

Can rot
Bad long term properties
Not as strong

139
Q

How can composites with continuous fibers be manufactured by injection molding?

A

Add the fibers in a controlled manner to the mould before injecting with plastic

140
Q

How is G3c normally measured for composite laminates?

A

Mixed mode bending test

141
Q

Name two common failure criteria for composite materials.

A

Maximum stress

Maximum strain

Tsai-Hill

Tsai-Wu

142
Q

What 2 groups can Failure criteria to predict lamina failure be divided into?

A

 Failure criteria not associated with failure modes

 Failure criteria associated with failure modes

143
Q

What does “Failure criteria associated with failure modes

“ consider? give examples on such failure modes

A

These criteria consider the different failure modes of the constituents.

Fiber fracture
 Transverse matrix cracking
 Shear matrix cracking

144
Q

What can “Failure criteria associated with failure modes” further be divided into?

A

 Non-interactive

 Interactive

145
Q

Describe the non-interactive Failure criteria associated with failure modes

A

The non-interactive criteria do not take into account interactions between
stresses/strains acting on a lamina. This often leads to errors in the strength
prediction when multiaxial states of stress occur in a structure.

146
Q

Give 2 examples of the non-interactive Failure criteria associated with failure modes

A

Maximum stress

Maximum strain

147
Q

Name some toughness tests

A

Charpy test used for plastics

Drop-weight impact often used for composites

148
Q

How can you get information on

 Energy for damage initiation
 Energy for penetration of the material/laminate
 Initiation and propagation of delaminations for different energy levels

A

Drop-weight impact test

149
Q

What is a TGA?

A

Thermogravimetric analysis

measure changes in material weight over T

150
Q

How can you get information on:

Quality control
Measurement of amount of additives
Measurement of amount of fibers

A

TGA

151
Q

What is a DSC?

A

Differential Scanning Calorimetry

difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature

152
Q

How can you get information on:

Measurement of glass transition temperature (Tg)
Measurement of crystallization
Measurement of degree of cure

A

DSC

153
Q

How can you:

 Measure the stiffness as a function of temperature
 Measure the stiffness as a function of loading frequency
 Measure the glass transition temperature (Tg)

A

DMTA

Dynamic Mechanical Thermal Analysis

154
Q

How does Dynamic Mechanical Thermal Analysis work?

A

Sinusoidial stress applied and strain measured

155
Q

What is NDT and what is it used for?

A

Non-destructive Testing
evaluate the properties of a material, component or system without causing damage. Generally not on the microscopic level.

156
Q

Name some examples of NDT

A

Visual inspection
magnifying glass

“Coin tapping”
look for delamination

Acoustic emission

Ultrasound
finds disbonding / delaminations / bigger voids

X-ray

Thermography

Shearography

Penetrant liquid

157
Q

What is important when it comes to Mechanical joining?

A

achieve load distribution over a large area

Beware of galvanic corrosion

158
Q

Describe Adhesive joining

A 
Wipe with solvent
Rinse with water or alkaline solution
Dry in oven
Lightly abrade to roughen matrix surface without exposing the reinforcement
Remove the abraded particles
Wipe with solvent
Rinse with water
Dry in oven
Bond as soon as possible
159
Q

Describe an alternative way of Adhesive joining

A

peel ply

160
Q

What is Important to make sure of when repairing?

A

that the repair is loaded in shear

161
Q

Bevelling ratio for marine and aircraft industry?

A

marine industry, 1:10

aircraft industry 1:50

162
Q

What’s the first step of repairing?

A

All damaged material must be removed

163
Q

What can you use when repairing?

A
  1. different laminates layers, finish up with a grinding layer
  2. use sandwich
    - take away as much core material as needed
    - can use glass microballoons in epoxy
164
Q

A sandwich laminate consists of three parts:

A

Adhesive, surface sheets, core:

Surface Sheet
Adhesive
Core material
Adhesive
Surface Sheet
165
Q

Name some Advantages with sandwiches

A

High specific stiffness and strength
Good thermal and acoustic insulation
High energy absorption
Buoyancy (flytkraft)

166
Q

Name some disdvantages with sandwiches

A

Manufacturing often difficult
Complicated quality control
Difficult with load introduction
Difficult to mechanically join

167
Q

What happens when you increase the amount of core material?

A

the Flexural rigidity and Bending strength increases

168
Q

Name some requirements on the surface material?

A

High stiffness

High tensile and compressive strength

good impact tolerance

good surface finish

good environmental resistance

good abrasion resistance

169
Q

Name some requirements on the core material?

A

Low density

High shear stiffness

High shear strength

High stiffness perpendicular to the surface sheets

Good thermal insulation

170
Q

Describe Load introduction

A

To disperse the force evenly:

  1. drill a hole
  2. take away more core material
  3. fill it with something
  4. insert the plug
171
Q

Name some advantages of Aramid fibers

A 
\+ High stiffness and strength
\+ Good impact properties
\+ Good insulation properties
\+ Good fatigue properties
\+ Good corrosion resistance
172
Q

Name some disadvantages of Aramid fibers

A
  • Poor compression strength
  • Poor UV-resistance
  • Sensitive to moisture
  • Expensive

Konstruktion i polymera kompositmaterial (1 decks)

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