1.1 Flashcards by Sandra Słoboda

What are the main reinforcement types?

Particles, Whiskers & nanofibers, Fibers

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What is the chemical composition of Asbestos?

Mg3(Si2O5)(OH)4

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What rocks is asbestos obtained from?

Serpentinite rocks

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Why was asbestos widely used?

Improved tensile strength, insulation, fire/heat resistance

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Why is asbestos banned?

Inhalation leads to lung cancer

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What is cellulose made from?

Condensation of glucose (C6H12O6 → -[C6H10O5]- + H2O)

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What is the degree of polymerization of cellulose?

≈ 10^4

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Which fibers are made of cellulose?

Cotton (80–85%), flax, hemp, jute

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What is the structure of vegetables?

Cellulose fibers embedded in hemicellulose + lignin

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What is collagen’s role?

Basic structural fiber in animals

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Where is collagen found?

Connective tissue: tendons, ligaments, skin

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What % of body protein is collagen in mammals?

25–35%

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What is collagen’s structure?

Triple helix of polypeptides stabilized by H-bonds

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What organisms produce silk?

Insects and spiders (spinning glands)

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What are silk fiber dimensions?

300 nm long, 1.5 nm diameter

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What is silk made of?

Amorphous protein (55–60%) + nanocrystalline protein

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What are silk’s properties?

High strength + ductility, tunable properties

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What type of polymer is aramid?

Aromatic polyamide (related to nylon)

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How are aramid fibers processed?

Spun from liquid crystalline polymer (H2SO4, 100°C, 20% conc.)

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What are aramid’s properties?

Strong, stiff, elongation 3.5–4%, good impact resistance

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What are aramid’s weaknesses?

Low compressive strength, UV sensitivity, anisotropic

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What is UHMWPE?

Ultra-high molecular weight polyethylene

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What is PE fiber density?

≈ 0.998 g/cm³

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How are PE fibers processed?

Gel-spinning, drawn at 120°C, draw ratio ≈ 200

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What are PE fiber properties?

Strong, stiff, elongation 3.5%, low density

What are PE fiber weaknesses?

Creep at ≈100°C, poor adhesion to matrices (needs plasma treatment)

What structure are carbon fibers based on?

Graphite (hexagonal basal planes)

What stiffness anisotropy do carbon fibers have?

≈1000 GPa in-plane, ≈35 GPa out-of-plane

What are carbon fiber processing routes?

Pyrolysis + graphitization of PAN or Pitch precursors

What are carbon fiber properties?

Strong, stiff, conductive, defect-sensitive, anisotropic

What is carbon fiber sizing for?

Protect surface + improve adhesion (epoxy, oxidative treatments)

What are glass fibers based on?

Amorphous SiO2 + metallic oxides

What are main glass fiber types?

E-glass, C-glass, S-glass

How are glass fibers processed?

Melt oxides → drawn fibers → sizing

What are glass fiber properties?

Isotropic, high strength, limited stiffness, degrade in moisture/alkaline, weak >500°C

Where are glass fibers used?

Low-cost reinforcement (construction, marine, automotive)

What are SiC fibers used for?

High-temperature applications

What are the two types of SiC fibers?

CVD-derived (β-SiC sheath + α-SiC core), Polymer-derived (SiC+SiO2+C)

What are CVD SiC fiber properties?

High modulus, stable at high T, expensive, non-weavable

What are polymer-derived SiC properties?

Flexible, cheap, low modulus, degrade >700°C

How are Al2O3 fibers made?

Sol-gel process, polycrystalline, ≈10 µm diameter

What are Al2O3 fiber properties?

Oxidation/fire resistant, insulating, low conductivity

What is Al2O3 fiber weakness?

Creep >700°C due to grain-boundary sliding

How are metallic fibers processed?

Wire drawing or Taylor process

What is metallic fiber structure?

Elongated grains, high defect density

What are metallic fiber properties?

High strength, low ductility, conductive, degrade with temp

What does fiber flexibility depend on?

∝ 1/(E*d^4)

What does the Weibull model describe?

Fiber failure based on defect distribution

How is fiber strength tested?

Tensile testing of N=30–50 fibers, Weibull modulus m, characteristic strength σ0

How long can asbestos fibers reach?

Several cm

What property of asbestos improved cement?

Tensile strength, insulation, resistance to fire/heat

What is the cellulose polymerization degree?

≈ 10^4

What % cellulose does cotton contain?

80–85%

What additional components make up plant structure?

Hemicellulose + lignin

What % of body protein does collagen represent?

25–35%

What stabilizes collagen's triple helix?

Hydrogen bonds

What is silk length and diameter?

300 nm long, 1.5 nm diameter

What proteins form silk?

Amorphous protein (55–60%) + nanocrystalline protein

What solvent is used in aramid fiber spinning?

H2SO4

At what concentration are aramid polymer solutions prepared?

≈20%

What temperature is used in aramid processing?

≈100ºC

What elongation to fracture can Kevlar 29 reach?

3.5–4.0%

What is the density of PE fibers?

≈ 0.998 g/cm³

What is the typical draw ratio in PE processing?

≈200

At what temperature are PE fibers drawn?

≈120ºC

What temperature causes PE creep?

≈100ºC

What bond strength do C–C bonds in graphite have?

≈525 kJ/m²

What is Van der Waals bond strength in graphite?

<10 kJ/m²

What is the carbon content after carbonization?

85–95%

At what temperatures is carbonization carried out?

1000–2000ºC in N2

At what temperatures is graphitization carried out?

2400–3000ºC in inert atmosphere

What are main precursors for carbon fibers?

PAN, Pitch

What defects limit carbon fiber strength?

Inclusions, voids

What is E-glass composition?

55% SiO₂, 19% CaO, 8% Al₂O₃, 7% Li₂O

What is C-glass composition?

65% SiO₂, 14% CaO, 9% Na₂O, 5% Li₂O, 4% Al₂O₃

What is S-glass composition?

65% SiO₂, 25% Al₂O₃, 10% MgO

What speed can glass fiber drawing reach?

≈50 m/s

What happens to E-glass in alkaline environments?

Corroded in cement

At what temperature do glass fiber properties decay?

400–500ºC

What is the diameter of polycrystalline SiC fibers?

≈100–150 µm

What chemical is used in CVD SiC processing?

CH₃SiCl₃

At what temperature does CVD SiC processing occur?

≈1000ºC

What is the composition of polymer-derived SiC fibers?

59% Si, 31% C, 10% O

What is the diameter of polymer-derived SiC fibers?

≈10–20 µm

At what temperature are polymer-derived fibers pyrolyzed?

≈1300ºC in vacuum

What diameter do Al2O3 fibers have?

≈10 µm

At what temperature are Al2O3 precursors calcined?

≈1400ºC

What diameter can metallic fibers reach by wire drawing?

Up to 100 µm

How are metallic fibers below 100 µm produced?

Taylor process

What factors must the glass sheath in Taylor process meet?

No reaction with metal, low viscosity, CTE ≈ metal, viscous before metal solidifies

What does fiber flexibility depend mainly on?

Fiber diameter

What is the Weibull modulus (m)?

Describes defect size distribution

What does characteristic strength (σ0) represent?

Average defect size

How many fibers are tested in tensile testing?

≈30–50

1.1 Flashcards

(94 cards)