Exam 2

Different types of glass reinforcements

• Roving (continuous-strand) • Unidirectional roving fabric • Woven roving • Chopped-strand • Chopped-strand mat • Continuous-strand mat • Roving/Continuous-strand mat • Knitted or textile fabric • Woven glass fabric • Milled fibers • Solid spheres • Hallow spheres • Porous spheres • Glass flakes

SPECTRA (Braided) 12-STRAND - Properties:

• Spectec-12 is a braided 12-strand synthetic fiber rope of 100% Spectra Fiber. • Specific gravity of 0.98. • Very high strength (one of the highest strength-to-weight ratios in a synthetic fiber rope). • Low stretch and easy handling. • Urethane coating provides abrasion resistance.

Describe the Stabilization process in the precursor-to-carbon-fiber conversion.

• Stabilization is carried out at temperatures below 400 °C in various atmospheres. • The fibers are stressed during this stage to improve the orientation of the molecular structure and increase carbon fiber strength and modulus. • All fiber-handling equipment is designed to minimize any damage throughout the conversion process.

What fiber properties do glass fibers have?

• Strength, • Flexibility, • Lightness of weight, and • Processibility.

Effect of heating (up to 500 oC) on properties of p-aramid fibers:

• The aromatic chemical structure of p-aramid has a high degree of thermal stability. • They do not have a literal melting point or a glass-transition temperature (Tg estimated, 375 °C) • They decompose in air at 425 °C • Inherently flame resistant. • Used at -200 to 200 °C, but short-term at temperatures above 150 °C because of oxidation. • Para-aramid fibers have: o Slightly negative longitudinal coefficient of thermal expansion of -2 × 10-6/K o A positive transverse expansion of 60 × 10-6/K • Has low thermal conductivity that is different in longitudinal versus transverse direction. • Combustion heat is about 35 MJ/kg.

What is chemical composition of Kevlar fibers?

• The chemical composition of Kevlar aramid fiber is poly para-phenyleneterephthalamide

Effect of Temperature on Spectra:

• The polyethylene fiber exhibits superior mechanical properties at ambient temperatures, its properties decrease rapidly with increasing temperature because of the relatively low melting point of the polymer. • Their melting temperature is between 144° and 152°C, depending on the testing method. • Above melting temperature, their firmness and length will decrease. • Should not use Spectra at temperatures above 80 to 100 °C for long periods of time. • It becomes brittle at temperatures below -150 °C. • They can be used in environments ranging from -150°C to about 120°C.

What is PPD-T stands for?

• This fiber is known as PPD-T because it is made from the condensation reaction of para-phenylene diamine and terephthaloyl chloride. • The aromatic ring structure contributes high thermal stability, while the para configuration leads to stiff, rigid molecules that contribute high strength and high modulus.

Synthesis of Ultra High Molecular Weight Polyethylene

• UHMWPE is synthesized from monomers of Ethylene. • These are molecules of polyethylene which are several orders of magnitude longer than familiar, high density polyethylene due to a synthesis process based on metallocene catalysts.

Mesophase Pitch Carbon fiber process and properties

• Upon prolonged heating above 400 °C, Mesophase pitch coalesces, solidify, and form regions of extended order. • Fiber is then carbonized at temperatures up to 1000°C. • The main advantage of this process is that no tension is required during the stabilization or the graphitization, unlike the case of rayon or PAN precursors. • Heating to above 2000 °C leads to the formation of graphite structure.

Processing Methods Dyneema

• Weaving fabric • Knitting clothing • Making ropes • Composite reinforcement

What is Mesophase Pitch?

(a) Mesophase Pitch is an intermediate high molecular weight aromatic phase, mainly anisotropic in nature formed during formation of carbon from a pitch precursor. It is a liquid crystal phase in the form of microspheres,

6. Name and describe the two basic processes that are used to manufacture continuous glass filaments.

1- Marble melt process: glass marbles are produced by melting raw materials and forming marbles. These marbles are then re-melted and formed into glass fiber products. 2- Direct melt process: raw materials are melted and formed directly into glass fiber product

Thermoplastic Composites Manufacturing Methods:

1. Compression Molding 2. Injection Molding 3. Extrusion 4. Blow Molding 5. Thermoforming

Thermosetting Composites Manufacturing Methods:

1. Hand Lay-up 2. Pre-preg forming 3. Compression molding 4. Vacuum bagging 5. Filament winding 6. Pultrusion 7. Spray method 8. Sheet molding 9. Bulk molding 10. Resin transfer molding (RTM)

Name some main advantages of Kevlar fiber. (at least 7)

1. High strength over weight ratio 2. Lower density than glass and carbon 3. Non-catastrophic failure 4. High elongation to break 5. Excellent fatigue and wear resistance 6. Good electrical properties 7. High toughness 8. Good chemical resistance 9. Negative coefficient of thermal expansion in longitudinal direction

What is Yarn?

An assemblage of twisted filaments, fibers, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving into textile materials used to reinforce plastics.

10. What is Tow?

An untwisted bundle of continuous filaments, usually referring to man-made fibers, particularly carbon and graphite, but also fiberglass and aramid.

Applications of High-Modulus Fabrics and Woven Rovings

Applications for high-modulus fabrics include: • Commercial aircraft and helicopter secondary composite parts, • Facings of honeycomb core constructions, • Boat hulls, • Electrical and electronic parts, • Ballistic systems, and coated fabrics.

The _________market has been, and is projected to continue to be, the largest consumers of reinforced plastics and composites.

Automotive

Applications of Dyneema

BALLISTIC VESTS - Lightweight vests - Dyneema UD (Uni-directional) - Low blunt trauma - Full Dyneema inserts LIGHTWEIGHT COMPOSITE ARMOUR - Lightweight armor - Easy to install - Lightweight helmet - Lightweight ropes

Name seven applications for the glass reinforced polymers as corrosion-resistant materials?

Corrosion-resistant materials cover a variety of markets. Major industries are: • Chemical processing, • Oil and gas, • Pulp and paper, • Waste water, • Air pollution control, • Electroplating • Underground gasoline storage tank • Work platforms • Walkways • Structural beams

What are the major characteristic (Properties) of three types of Kevlar Fibers?

Kevlar 29 is used in composites for its • Higher toughness, • Damage tolerance, or • Ballistic stopping performance Kevlar 49 is the dominant form used today in structural composites because of its higher modulus. Kevlar 149 or ultra-high-modulus fiber are also available.

What are a the four examples of non-commercialized glasses?

M-glass or Beryllium oxide glass, lead glass, D-glass, and lithium oxide based glass.

How are reinforcing mats made?

They are made with randomly dispersed chopped fibers or continuous fiber strands, laid down in a swirl pattern

Name five of the seven typical fiber weaves.

leno, plain, 8 hardness satin, 3x1 twill, crawfoot satin, basket, and high modulus fabric weaves.

What is the primary weave used in the coating industry?

Plain Fabric Weave.

What are the different types of milled fibers?

Powder and floccular

What is the advantage of Leno fabric?

Prevent the shifting of fibers in open-weave fabrics.

What glass fiber type would you expect to use in poltrusion processes and why?

Roving fiber would be used because it is collected into a parallel bundle with little or no twist.

Important glass formers.

Silica sand, limestone, feldspar, soda ash, salt cake, gypsum, sodium nitrate, borate materials, lead oxides and silicates.

Dyneema or Spectra Fiber Properties

1. It is a highly crystalline very tough material, with the highest impact strength of any thermoplastic presently made. 2. It is both high-strength and high-modulus fiber. 3. It is highly resistant to corrosive chemicals, with exception of oxidizing acids. 4. It has extremely low moisture absorption, 5. It has very low coefficient of friction 6. It does not contain any aroma, amides, hydroxyls or any other chemicals susceptible to attacks from aggressive (organic) agents. 7. It is odorless 8. It is nontoxic 9. It is self lubricating 10. It is highly resistant to abrasion (10 times more resistant to abrasion than Carbon Steel) 11. It is highly resistant to chemicals 12. It is highly resistant to microorganisms 13. It is highly resistant to water 14. It is highly resistant to UV light 15. It is highly resistant to flex fatigue 16. Excellent vibration damping 17. Low dielectric constant make it transparent to radar 18. Its coefficient of friction is significantly lower than nylon, and is comparable to Teflon and has better abrasion resistance than Teflon. 19. The fibers do not expand in water, salt water, or from moisture

What are some of the main disadvantages of Kevlar? (at least 4 points)

1. Poor compression strength 2. Expensive 3. Sensitive to UV light 4. Difficulty in cutting and machining 5. Fiber fragmentation and splintering and localized drawing

16. What is the range of fiber length in Chopped Strand?

3 mm to 50 mm

55. Define pitch

A high molecular weight material that is a residue from the destructive distillation of coal and petroleum products.

14. Describe a Roving:

A number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.

Define Denier:

A textile unit of size, is the weight in grams of 9000 meters of yarn or roving

Why are composites used in "stealth" technology in the military?

Because of their radar transparency.

18. What advantages do both forms of milled fiber offer?

Both powder and floccular milled glasses offer: - Dimensional stability, - Shrinkage control, - High modulus - Acid resistance in applications - Control heat distortion of the resin - Improve surface finish of molded parts

How is woven fiber constructed?

By interlacing yarns, fibers, or filaments to form such fabric patterns as plain, harness satin, and leno weaves.

How is nonwoven fabric produced?

By loosely compressing together fibers, yarns, rovings, and so forth. Accomplished by mechanical, chemical, thermal, or solvent means, or combinations thereof

What type of precursor produces higher tensile strength carbon fiber than the fibers based on other precursors? What is the reason for their high strength property?

Carbon fiber based on a PAN precursor generally has a higher tensile strength than a fiber based on any other precursor. This is due to a lack of surface defects, which act as stress concentrators and therefore reduce tensile strength.

Describe Continuous fiber strands:

Consist of fibers that extend throughout the entire length of the strand.

NOMEX:

DuPont's family of NOMEX® fiber products provides heat and flame resistance and good textile properties.

What are the common glass fiber types, and what are their specific properties?

E- Electrical: low electrical conductivity. S- Strength: high strength. C- Chemical: high chemical durability. M- Modulus: high stiffness. A- Alkali: high alkali or soda lime glass. D- Dielectric: low dielectric constant.

What are the steps in production of Carbon fibers from Isotropic Pitch?

Isotropic pitch is melt spun at high strain rates to align the molecules parallel to the fiber axis. The thermoplastic fiber is then rapidly cooled and carefully oxidized at a low temperature (<100°C). Upon carbonization, relaxation of the molecules takes place, producing fibers with no significant preferred orientation.

Name five applications of the glass reinforced polymers in the electrical/electronic market.

• Printed circuit boards, • Composite ladders, • Poles, • Industrial circuit breaker housings, • Conduits for power cables to provide protection against electrical shock

What is the smallest unit for fiberous material?

Filament

15. What are typical end-use processes and applications of continuous rovings?

Filament winding, pultrusion, knitting and weaving, and thermoplastic processing to manufacture products such as pipe, ladders, telecommunication cables and automotive parts.

What are the three types of glass spheres?

Hollow, Porous, Solid

What are the different forms of carbon?

I. Carbon Black: Amorphous carbon structures have been obtained by means by incomplete combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. II. Graphite: is one of the standard forms of carbon. The atoms are arranged in sheets, in a hexagonal pattern like chicken wire. The sheets lie on top of each other. III. Diamond IV. Carbon 60 Buckyballs V. Carbon Nanotube VI. Graphene

What advantages does the powdered form of milled fibers possess?

In the powder form, milled fibers have better flowability with high bulk density, which results increased productivity and lower manufacturing costs.

What are the major applications of p-aramid fibers?

Numerous aramid fiber forms support commercial applications in: • Composite components • Ballistic products • Tires • Ropes and cables • Asbestos replacement • Protective clothing

Briefly explain toughness properties of Para-aramid fiber

Para-aramid fiber shows • High toughness (the area under the stress-strain curve) and general damage tolerance characteristics. • Impact resistance and ballistic stopping power. • Provides composites fail in a ductile, or noncatastrophic manner, as opposed to glass and carbon.

What type of Pitch precursors used to produce carbon fiber are:

Petroleum asphalt Coal tar Polyvinyl chloride

What type of precursors are used for the manufacture of certain high-modulus carbon fibers?

Pitches

What is one advantage and one disadvantage of Pitch precursors

Pitches are relatively low in cost and high in carbon yield. Their most significant drawback is nonuniformity from batch to batch.

What are the advantage and disadvantage of Rayon precursors?

Their advantages is that they are well characterized and readily available Their most significant disadvantage is a relatively high weight loss, or low conversion yield to carbon fiber.

47. What are the major carbon fiber precursors (feedstocks)?

• Rayon • Polyacrylonitrile • Petroleum pitch

What are glass flakes used for in resinous coatings?

To increase resistance to permeability from moisture, vapor, and solvents

48. What are the different steps in the processes of precursor-to-carbon-fiber conversion?

a. Stabilization (oxidation) b. Carbonization c. Graphitization (optional) d. Surface treatments e. Application of sizings or finishes f. Spooling

Carding

• A process of untangling and straightening fibers by passing them between closely spaced surfaces, moving at different speeds, one of which is covered in sharp points.

Military Applications:

• A product of Honeywell's advanced ballistic technology, is an advanced non-woven composite • The plates are only four pounds each, strong enough to stop rounds from an AK-47. • Used in military vehicles, now also used by U.S. soldiers as lightweight inserts worn in an Interceptor vest to ward off bullets and shrapnel.

Name five applications of the glass reinforced polymers in Aircraft/Aerospace/Military Market.

• Both commercial and military aircraft make extensive use of reinforced plastic materials • Helicopter rotor blades • Aircraft wing and • Tail components • Engine ducts • Because of their radar transparency, advanced composites play a key role in Radar-evading "stealth" technologies • Protective armor against ballistics attack

How do carbon fibers react with molten aluminum and titanium, nickel, and metal oxides?

• Carbon fibers react with molten aluminum and titanium and must be protected by a barrier coating. • While carbon does not react with nickel, a small amount of solution/dissolution can occur (even in the solid state), which degrades the fibers.

Describe Carbonization process in the precursor-to-carbon-fiber conversion.

• Carbonization is accomplished at temperatures from 800 to 1200 °C • The stabilized fibers are pyrolyzed in inert environments to reduce their impurity levels and increase their crystallinity. • Fibers may be shrunk or stretched in this step. • Any increase in orientation generally increases tensile modulus.

How does molecular structure of Kevlar differ from conventional polymers?

• Conventional flexible polymers can bend and entangle in solution, forming random coils. • Para-aramid fibers are liquid crystalline polymers. • These polymers are very rigid and rodlike, in solution they can aggregate to form ordered domains in parallel arrays. • Conventional organic are characterized by chain folds, misalignment, and crystalline or amorphous regions. • Para-aramid, characterized by long, straight chains without folds, parallel to the fiber axis, crystalline

Name six applications for the glass-reinforced polymers in the automotive industry.

• Exterior body panels. • Drive shafts • Wheels • Leaf springs • Headlamp housings, • Spare tire covers, • Bumper beams, • Hood/fender assemblies, • Engine components for heavy-duty trucks, • Body panels and engine components for recreational vehicles,

NOMEX Applications

• Filters, • Industrial coated fabrics, • Electrical insulation in both paper and pressboards • Nomex®-Kevlar® blends are used to make flame-resistant clothing that protects firefighters, race drivers, and jet pilots.

What is the problem on using carbon fiber at elevated temperature? How can this problem be reduced?

• For low-modulus PAN-based fibers threshold for oxidation for extended operating times is 350 °C • For high-modulus PAN- or pitch-based fibers, the threshold for oxidation for extended operating times is 450 °C • Oxidation is catalytic at these low temperatures; improved oxidation resistance can be expected with higher-purity fibers and resins.

Describe Graphitization process in the precursor-to-carbon-fiber conversion.

• Graphitization is an optional pyrolysis step that is in excess of 2000 °C in inert environments. • This step also reduces the level of impurities and stimulates crystal growth. • The higher the process temperatures used in carbonization and graphitization processes, the higher the modulus of the resultant fibers.

Dyneema or Spectra Processing:

• HDPE molecules generally have between 700 and 1,800 monomer units per molecule, while UHMWPE molecules tend to have 100,000 to 250,000 monomers each. • The polymers are aligned randomly when they are produced. • To make fibers like DYNEEMA or SPECTRA, they are dissolved and drawn into fibers as the solvent evaporates, causing the polymer chains to orient in the direction of the fiber.

What familiar bulk glass properties do glass fibers have?

• Hardness, • Transparency, • Resistance to chemical attack, • Stability, and • Inertness,

Applications of Fabrics and Woven Rovings

• Heavy, woven roving fabrics are used in marine applications where hand lay-up is appropriate and for ballistic fabrics and aircraft cargo liners. • Unidirectional fabrics are used when maximum properties are desired in one direction.

SPECTRA 12-STRAND Applications:

• Merchant Marine • Industrial • Utility • Rescue • Commercial Fishing.

What are the environmental factors that do not affect Carbon fibers properties at room temperature?

• Moisture, • Atmosphere, • Solvents, • Bases, • Weak acids

What are the major construction applications for the glass-reinforced polymers?

• Paneling • Skylights • Bathtubs • Shower stalls • Doors, and windows

Briefly explain environmental behavior of p-aramid fibers.

• Para-aramid fiber has an equilibrium moisture content that is determined by the relative humidity. • Para-aramid fiber can be chemically degraded by strong acids and bases. • It is resistant to most other solvents and chemicals • Ultraviolet radiation also can degrade p-aramid. The degree of degradation depends on material thickness because p-aramid is self-screening. • In polymeric composites, strength loss of p-aramid has not been observed.

What are the applications for the glass-reinforced polymers in the marine industry?

• Pleasure boats • Sailboards • Hulls and decks of commercial fishing boats • Military minehunters