Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

APSC 278 (Engineering Materials) > composites > Flashcards

composites Flashcards

(59 cards)

Start Studying
1
Q

What are composites?

A

Materials with more than 1 phase present, each of which
are chemically dissimilar and separated by a distinct interface.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the phases of most composite materials?

A

The matrix and the dispersed or reinforcing phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the phases of concrete?

A
  1. Cement
  2. Aggregate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the phases of reinforced concrete?

A
  1. Cement + Aggregate
  2. Rebar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the phases for eutectoid steel?

A
  1. Ferrite
  2. Cementite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the phases for wood?

A
  1. Cellulose fibers
  2. Lignin and hemicellulose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the applications of composite materials?

A
  1. Aerospace
  2. Underwater
  3. Transportation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the beneficial material properties of composites?

A
  1. Low density
  2. High stiffness
  3. Small coefficient of thermal expansion
  4. Fatigue and impact resistant
  5. Corrosion resistance
  6. High modulus-to-weight ratio
  7. High strength-to-weight ratio
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can the matrix phase consist of?

A
  • metals (Al, Ti)
  • ceramics (Al2O3, ZrO2)
  • polymers (epoxy, polyester, phenolic)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What types of geometries can be in the reinforcing phase?

A
  • fibres
  • particulates
  • whiskers (single crystal with nearly zero defect)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the most widely used and studied composite structure?

A

Fibre & polymer matrix composites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are fiber-based composites?

A

Usually combinations of fibres made
from ceramic, polymer, or glass
embedded in a polymer matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the typical range of % volume of fiber in fiber-based composites?

A

Typically 40
-60 % fiber by volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the common patterns for fibre-based composites?

A

Characteristic ”weave” pattern (e.g.
carbon fibre), or less organized fibre
patterns with randomized cut fibres
(e.g. fiberglass
-based chairs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the advantages of fiber-based composites?

A

-good combination of
stiffness, density and fracture
toughness.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the disadvantages of fiber-based composites?

A

-often expensive
-May be difficult to process
-Often difficult to detect damage (cracks).
-Ideally suited to withstand tension,
not compression.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do all fiber materials have in common?

A

All fiber materials are high performance (high strength and stiffness)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are common matrix materials in composites?

A

Polyesters, vinyl esters, polyimides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the role of the matrix regarding the separation of fibres and crack propagation of fibres?

A

It separates the fibres and stops cracks from propagating directly
from fibre to fibre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why must the matrix bind to fibres very well?

A

To protect them from external damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does the matrix transmit to the fibres in composites?

A

Transmits external loads to the fibers, while carrying only a small
fraction of the load itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the density and ductility of matrix in composites.

A

Typically low density, relatively ductile materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the most common fibre materials?:

A
  • glass (fiberglass)
  • carbon
  • Spectra (Polyethylene)
  • Kevlar (aramid, a type of polymer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is the high strength of fibres achieved?

Study These Flashcards
A

Due to low probability of flaws in
individual fibres

25
What are the properties specific to carbon fibers?
high specific modulus and specific strength compared to all fibre materials.
26
What type of version are carbon fibres compared to carbon?
A semi-crystalline version of carbon.
27
What does anisotropic mean?
mechanical behavior is direction-dependent
28
What are the two cases to determine the upper and lower bounds of fibre-based composites?
Isostrain vs. isostress
29
What does isostrain represent?
-The ideal arrangement as the composite structure has been optimized for loading direction -Upper bound for overall performance
30
What does isostrain mean in terms of how the fibres are oriented?
The fibers oriented parallel to force.
31
How is the stiffness of the overall material determined in isostrain analysis?
By the stiffness and volume fractions of the fibre and matrix.
32
What does isostress mean in relation to the orientation of fibres?
All of the fibers are oriented perpendicular to the applied forces
33
How is the isostress analysis modelled to make it easier to analyze?
Instead of considering individual fibres, we represent this with layers of matrix and fibre-type material interspersed with one another
34
Which of the following values are equivalent to each other in isostrain conditions?
The strain of the composite = fibre strain = matrix strain
35
Which of the following values are equivalent to each other in isostress conditions?
Composite stress = matrix stress = fibre stress
36
How can the fiber performance be maximized?
It is desirable to have all fibers as long as possible, and oriented in the direction of greatest tension.
37
Why are fibres either "discontinous and aligned" or "randomly oriented"
To allow easier fabrication of the composite.
38
How can fibers be more isotropic?
Randomly oriented fibers also makes the material more isotropic.
39
Compare the ductility of fibre and matrix in a fibre composite
-The fibre is to be totally brittle -The matrix is to be reasonably ductile
40
What type of stress response will an aligned fiber composite exhibit?
A uniaxial stress-strain response
41
What happens in Stage I of the uniaxial stress-strain response of an aligned fiber composite?
Stage I - both fibres and matrix deform elastically
42
What happens in Stage II of the uniaxial stress-strain response of an aligned fiber composite?
Stage II - the matrix starts to yield as the fibres continue to deform elastically
43
What happens to the load from Stage 1 to Stage II in the stress-strain behaviour of an aligned fiber composite?
The proportion of load carried by the fibres increases
44
What happens to the fractured fibres during the stress-strain response of an aligned fibre composite?
* These fractured fibres, now shorter, are still embedded within the matrix and are capable of sustaining a smaller load as the matrix is plastically deformed.
45
At what condition is the tensile strength of a fibre determined predominantly by the fibre tensile strength?
When fibres are oriented in the direction of the tensile force (0°)
46
When is the weakest link the strength of the matrix for a composite sample?
When the sample is oriented with the fibres perpendicular to tensile axis (90°)
47
Where do all of the other orientations fall based on the strength of fibre composites?
All other orientations fall between these two extremes
48
What stops cracks from propagating in the composite?
The matrix.
49
What is the primary load carrier in composite?
Fibers
49
What are the mechanical properties of fiber-reinforced composites influenced by?
- Properties of constituents - Fiber orientation - Fiber length and volume fraction
50
When does the onset of composite failure begin?
When fibres start to fracture.
51
Compare the Young's Modulus of the aligned composite to the matrix and fiber during a uniaxial stress-strain response.
The Young’s modulus of the composite is higher than the matrix and lower than fiber.
52
Compare the ductility of the aligned composite to the matrix and fiber during a uniaxial stress-strain response.
The ductility of the composite is lower than the matrix and higher than fiber.
53
Compare the fracture strength of the aligned composite to the matrix and fiber during a uniaxial stress-strain response.
The fracture strength of the composite is higher than the matrix and lower than fiber
54
Compare the Young's Modulus of parallel carbon-fiber composites to perpendicular carbon-fiber composites at the same density.
Parallel carbon-fibre composites have a greater Young's Modulus than perpendicular carbon-fibre composites.
55
Which type of composite analysis represents the best-case scenario?
Isostrain analysis
56
Which type of composite analysis represents the worst-case scenario?
Isostress analysis
57
What type of composite analysis does a longitudinal modulus of elasticity refer to?
Isostrain analysis (fibres oriented parallel to force)
58
What type of composite analysis does a transverse modulus of elasticity refer to?
Isostress analysis (fibers oriented perpendicular to force)

APSC 278 (Engineering Materials) (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions