Fiber Reinforced Composites > Remainder > Flashcards

Remainder Flashcards

(69 cards)

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1
Q

Special aspect of tensile testing for composites

A

Use of end tabs

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2
Q

Materials used for end tabs in tensile testing of composites

A

E-glass-epoxy

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3
Q

Purpose of end tabs for tensile testing of composites

A

To reduce stress concentration in gripped area and promote tensile failure mode

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4
Q

Tensile testing off-axis means

A

Fibers not aligned with pull direction

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5
Q

Tensile-testing extensional stiffness matrix complication

A

A16, A26 != 0

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6
Q

Shape of deformation expected in off-axis tensile testing

A

S-shaped deformation

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7
Q

Comparison of stress-strain curves for CF vs. GF

A

CF has higher modulus, higher strength, lower elongation

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8
Q

Stress-strain curve for tensile-cross-ply laminate

A

Contains a knee, representing failure of 90 ply

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9
Q

Significance of first knee in multi-directional laminate stress-strain curve

A

Failure of first ply

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10
Q

FPF acronym

A

First ply failure

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11
Q

Failure prediction acronym: SLT

A

Longitudinal tensile strength

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12
Q

Failure prediction acronym: SLTS

A

In-plane shear strength

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13
Q

Destructive inspection techniques

A

Microscopy

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14
Q

Microscopy D/ND?

A

Destructive

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15
Q

Non-destructive inspection techniques

A

Coordinate measurement, ultrasound, thermography

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16
Q

Coordinate measurement D/ND?

A

ND

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17
Q

Ultrasound D/ND?

A

ND

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18
Q

Thermography D/ND?

A

ND

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19
Q

Defects examined in manufacturing inspection

A

Porosity, delamination, poor cure, resin-rich/resin-poor areas

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20
Q

Defects examined in in-service inspection

A

Cracks, delamination, trapped water, hole damage, burns

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21
Q

Thermal profile of thermoplastic manufacturing

A

Highest temp after heating; convection losses in transport; conduction losses in forming and consolidation

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22
Q

Manufacturing of thermoplastic composites

A

Heating, transport, forming, consolidation, demolding

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23
Q

Thermoplastic vs. thermoset viscosity

A

Lower viscosity needed for thermoplastics

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24
Q

Important difference of thermoplastics vs. thermosets

A

Thermoplastics can be softened and remolded.

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25
Thermoplastic advantages vs. thermosets
No refrigeration needed, long shelf life, short processing, high toughness, remeltable, recyclable, fusion bonding
26
Thermoplastic disadvantages vs. thermosets
High melting viscosity results in voids; residual stress from thermal expansion; crystallinity from slow cooling rates
27
Three types of welding
Resistance welding, induction welding, ultrasonic welding
28
Welding can only be used with what type of composite
Thermoplastic composites
29
Ultrasonic welding description
Parts are held together under pressure with an energy director between them; a sonotrode is used to apply ultrasonic (20-50 kHz) vibrations creating heat for welding
30
Induction welding description
Parts are held together with a susceptor between them; an alternating magnetic field generates heat used to weld them together.
31
Speed ranking of joining methods:
Ultrasonic > induction > resistance > adhesive
32
Resistance welding description
Parts are held together via insulating blocks with a heating element between them. Electric current is passed through heating element, forming a weld
33
Machining is not preferred compared to
Manufacturing and curing to net shape
34
Traditional machining methods include
Turning, drilling, milling, sawing
35
Non-traditional machining methods include
Water jet cutting, laser machining, electric discharge machining
36
Drilling vs. milling
Drilling motion is along axis of rotation; milling is perpendicular to axis of rotation
37
Special drill bit needed for composites
Polycrystalline diamond drill bits or submicron diamond particle coated drill bits
38
Why special drill bit needed for drilling composites
Carbon fiber composites are very abrasive
39
Why sawing composites is difficult compared to other materials
CF is abrasive and does not transfer heat very well; saws can result in delamination
40
Special saws needed for composites
Diamond tip/WC grit saw blade with special tooth design (non-tooth-style)
41
Waterjet machining composites
High pressure (90k psi) water with abrasive material to cut CFRP
42
Waterjet advantages
Fast, low heat, no cutting blade, dust prevented
43
Waterjet disadvantages
Edge finish, tapered edge, high capital investment, high operating cost
44
Waterjet tapered edge caused by
Bend from fixturing
45
Lasercutting advantages
High accuracy, no cutting force
46
Lasercutting disadvantages
HAZ, low cutting speeds for thick parts, high capital investment, hazardous volatiles
47
Two types of joining methods
Mechanical fastening & adhesive bonding
48
Steps of mechanical fastening
Machine structure, select appropriate fastener, assemble & inspect
49
Primary advantage of mechanical fastening
Disassembly
50
Primary disadvantage of mechanical fastening
Stress concentration
51
Geometric parameters of concern in mechanical fastening
e/d, w/d, h/d, spacing
52
e/d mechanical fastening
edge distance to bolt hole diameter
53
w/d mechanical fastening
width to bolt hole diameter
54
h/d mechanical fastening
laminate thickness to bolt hole diameter
55
Failure modes in bolted laminates
shear-out, net tension failure, cleavage, bearing failure
56
Preferred failure mode in bolted laminates
bearing failure
57
How to generally optimize mechanical fastening parameters
Increase ratios and spacing
58
Steps of adhesive bonding
Prepare surface, apply adhesive, co-cure
59
Surface prep for composite laminates
Use abrasive/nylon cloth in vacuum bag and remove prior to bonding; dry prior to bond
60
Bond joints in order of strength increasing
Single lap, double lap, single/double strap, stepped lap, scarf joint
61
Advantage of adhesive bonding
Load distributed across large area, better for large integrated structures
62
Disadvantage of adhesive bonding
Permanent, sensitive to surface prep, limits service conditions
63
Surface preparation of metal ranked by bond strength
Anodize > grit blast > degrease
64
Epoxy adhesive important points
High moisture and temperature are bad for adhesion strength
65
Fiber orientation distribution (SFC) is affected by
Original distribution, fiber concentration, matrix properties, mold design, process temp. and pressure.
66
How flow affects fiber orientation distribution
Shear flow aligns in flow direction; extensional flow aligns perpendicular to flow.
67
Common fiber orientation direction
Skin in longitudinal, core in transverse
68
Sandwich components
Facesheet, core, adhesive
69
Sandwich manufacturing methods
Bonding (pre-cured) vs. co-cure (uncured adhesive + prepreg)
Fiber Reinforced Composites
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