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Book used to cover the manufacturing aspects

Composites Manufacturing: Materials, Product, and Process Engineering [CRC press], 2001 Sanjay Mazumdar (Author)

http://www.amazon.com/s/ref=ntt_athr_dp_sr_1?_encoding=UTF8&field-author=Sanjay Mazumdar&search-alias=books&sort=relevancerank

http://www.amazon.com/s/ref=ntt_athr_dp_sr_1?_encoding=UTF8&field-author=Sanjay Mazumdar&search-alias=books&sort=relevancerank

Evolution of Engineering materials

Fleck, N. A., V. S. Deshpande, and M. F. Ashby. "Micro-architectured materials: past, present and future." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science 466.2121 (2010): 2495-2516.

Conventional Engineering Materials and examples A

lloys

Metal properties: high stiffness, strength, thermal stability, thermal/electrical conductivity. Sustain high service temperatures, mostly machinable

Plastics: the production of plastics on a volume basis has exceeded steel production. They are not for high temperature applications, usually <100C, rarely up to 200 C, easy to form in shape

Ceramics: great thermal stability, high hardness, very rigid compared to all materials, almost no ductility, brittle, high chemical resistance, used high-temperature and high-wear applications, hard to cut and form in shape

Composites: lightweight, when replaces steel that save 60 to 80% weight and when replace alumunim they replace 20-50%. They have the weaknesses of polymers

What Are Composites?

In general, A composite material is made by combining two or more materials to give a unique combination of properties.

Example of composites: metals alloys, plastic co-polymers, minerals, wood, and fiber-reinforced composites.

Fiber-reinforced composite materials the constituent materials are different at the molecular level and are mechanically separable (so they are very heterogeneous). The final properties of composite materials are better than constituent material properties

Composites are associated with a wide range of length scales, down to the nano range

Basics idea behind Fiber-reinforced composite materials

nonstructural applications structural applications

Fabrication: Injection, compression molding

Fabrication: filament winding, pultrusion, roll wrapping , and layup

Are scale and microstrure related to composite fabrication?

Basics two classed of Fiber-reinforced composite materials

Functions of Fibers and Matrix

Fibers: • Carry the load. In a structural composite, 70 to 90% of the load is carried by fibers. • Provide stiffness, strength, and structural properties

Matrix: • material binds the fibers together and transfers the load to the fibers. • It provides rigidity and shape to the structure. • The matrix isolates the fibers so that individual fibers can act separately. • The matrix provides a good surface finish quality • The matrix provides protection to reinforcing fibers against chemicals and wear • Assists in providing ductility, impact strength, etc. A ductile matrix will increase the toughness of the structure. For higher toughness requirements, thermoplastic-based composites are selected. • The failure mode is strongly affected by the type of matrix material used in the composite as well as its compatibility with the fiber.

Advantages Composites

• high specific stiffness (stiffness-to-density ratio). Composites offer the stiffness of steel at one fifth the weight and equal the stiffness of aluminum at one half the weight.

• High specific strength (strength-to-density ratio). The specific strength is typically in the range of 3 to 5 times that of steel and aluminum alloys.

• High fatigue strength (endurance limit). Unidirectional carbon/epoxy composites have good fatigue strength up to almost 90% of their static strength, (50% for steel or aluminum alloys)

• high corrosion resistance.

• Good impact properties

• Easy to shape into curved surfaces

Drawbacks of Composites (but there are efforts to lessen them)

• Material Cost (5 to 20 times more than steel/aluminum per weight)

• Low volume production. Solutions to increase the rates include automated (pultrusion, resin transfer molding (RTM), structural reaction injection molding (SRIM), compression molding of sheet molding compound (SMC), and filament winding have been automated for higher production rates.

Drawbacks of Composites (but there are efforts to lessen them)

• Material Cost (5 to 20 times more than steel/aluminum per weight)

• Low volume production. Solutions to increase the rates include automated (pultrusion, resin transfer molding (RTM), structural reaction injection molding (SRIM), compression molding of sheet molding compound (SMC), and filament winding have been automated for higher production rates.

• Lack of design databases and handbooks (contrary to metals where metal design handbooks are widely available)

• Functionality is limited to a restrictive range of temperatures (depending on the polymer)

• Prone to degradation due to moisture.

• Some composites depending on their polymer can be degraded due to corrosion

Composites Processing

(RTM): resin transfer molding, (SRIM): structural reaction injection molding (SMC): compression molding of sheet molding compound

Composites product fabrication

Forming, machining, assembly, and finishing

Composites Markets

Transportation industry is the largest user of composite materials (1.3 billion pounds of composites in 2000)

the price of carbon fiber decreased from $150.00/lb in 1970 to about $8.00/lb in 2000

composites : aerospace, automotive, construction, marine, corrosion resistant equipment, consumer products

600,000 lb of composite material used in top of-the-line bicycles, which sell in the range of $3000 to $5000 per unit.

Marine composites: mainly glass-reinforced plastics (GRP) with foam and honeycomb as core materials

70% of all recreational boats are made of composite materials

United States was $8.85 billion and total composite shipments in the boating industry worldwide is estimated as 620 million lbs in 2000.

Raw Materials for Part Fabrication

Matrix Materials

Thermoset Resins:

Epoxy: • Costly but Most widely used • varying grades of epoxies with varying levels of Performance • cure rate and temperate processing requirement can modified • Epoxies can operate at relative high temperature (200 to 250°)F, and some can go up to

400°F. • Epoxies can be bought in three forms (liquid, solid, semi-solid) each form is suitable for

particular fabrication method • generally brittle

Thermoplastic Resins

Thermoset Resins: • after curing (cross-linking) they cannot be melted of reformed. • With increased cross-linking density, they become more rigid and thermally stable. • Too much cross-linking, they become more brittle • easier to process as they can cure at room temperature • greater thermal and dimensional stability, better rigidity, chemical, and solvent

resistance


Phenolics : • Satisfied the requirements for low smoke and toxicity. Therefore, used for aircraft

interiors, stowbins, and galley walls • water is generated during cure reaction • are used in exhaust components, missile parts, manifold spacers, commutators, and disc

brakes

Polyesters : • Low cost • Low operating service temperatures • excellent corrosion resistance • Can thermoplastic or thermoset

Vinylesters • Good chemical and corrosion resistance • FRP pipes and tanks in the chemical industry • Better ductility and toughness that epoxies and polyester • Cheaper than epoxies

Cyanate Esters • excellent strength, toughness, better electrical properties, and lower moisture

absorption compared to other resins. • spacecrafts, aircrafts, missiles, antennae


Bismaleimide (BMI) and Polyimide: • Glass transition temperature (Tg) of BMIs is in the range of 550 to 600°F much higher

than for other resins. • Low toughness • Difficult to process

Polyurethane : • Used in automotive applications (e.g. bumper beams, hoods, body panels) • Used to make foams for seats • Can be thermoplastic or thermoset • excellent wear, tear, and chemical resistance, good toughness, and high resilience.

Thermoplastics : • ductile and tougher than thermosets • used for a wide variety of nonstructural applications • repeated reshaping and reforming by the application of heat • Poor creep resistance (especially at high temperatures) as compared to thermosets • More susceptible to chemicals and solvents than thermosets • Can be welded together (so repair and joining of parts is more simple than for

thermosets • Require higher forming temperatures and pressures than thermosets • higher viscosity than thermosets (affect manufacturing processes where flow is

required) • Is a research area.


Nylon: • Also called polyamides. • There are several types of nylon (e.g. nylon 6, nylon 66, nylon 11) • absorb moisture • Good surface appearance and good lubricity • used for making intake manifolds, housings, gears, bearings, bushings • available as prepregs • With glass reinforcements, they can provide good impact-resistance ( better than

aluminim and magnesium)


Polypropylene (PP): • low-cost and low-density (less than water) • good strength, stiffness, chemical resistance, and fatigue resistance

Polyetheretherketone (PEEK): • Relatively new and very costly (50$/lb) with processing temperature 380 to 400°C • Can service at high temperatures (250C) • Carbon-reinforced PEEK composites (APC-2) are used in fuselage, satellite parts, and aerospace structures • greater damage tolerance, better solvent resistance • PEEK has the advantage of almost 10 times lower water absorption than epoxies.

Aerospace grade composites have 4 to 5% water absorption at room temperature • 50 to 100 times higher than that of epoxies

Polyphenylene Sulfide (PPS): • Can service at high temperatures (225C) • It is processed in the temperature range of 300 to 345°C • Prepreg systems with PPS are commercially availed (e.g. Ryton and Techtron) • PPS-based composites are used for applications where great strength and chemical

resistance are required at elevated temperature.

Thermoplastics :


Thermosets:


Reinforcements (glass, carbon ,aramid, boron fibers)

• Typical carbon fiber diameters range from 5-8, glass fiber 5 -25 mm, aramid fiber is 12.5 mm and boron fiber 100mm

• Fibers are thin, bendable and easy to conform to various shapes. • In general, fibers are made into strands for weaving or winding operations. • For delivery purposes, fibers are wound around a bobbin and collectively called

a “roving.” • An untwisted bundle of carbon fibers is called “tow.”

Woven Fabrics Nonwoven (Noncrimp)Fabrics

Prepregs

Fibers are commercially available in multiple forms

Fabrics

Woven Fabrics

Fabrics

• The amount of fiber in different directions is controllable. For example, a unidirectional woven fabric has 95% (weight wise) of its fibers aligned with 0° direction.

Nonwoven (Noncrimp) Fabrics

bi-ply fabric

examples

Prepregs

• A prepreg is a flat shaped resin pre-impregnated fiber, fabric, or mat, which is stored for later use

• Unidirectional prepregs: Fibers are laid at 0° • Unidirectional tape is used to build multi-directional laminates • Woven fabric prepregs are used to make highly contoured parts and sandwiched

structures with honeycomb cores for aerospace applications • Preimpregnated rovings are primarily used in filament winding applications

• Epoxy-based prepregs come thickness range of 0.127 mm (0.005 in.) to 0.254 mm (0.01 in.)

• Available as thermoset-based or thermoplastic-based

• Unidirectional prepregs are available in widths ranging from 0.5 to 60 in. • Weave based prepregs are availed in widths ranging 39 to 60 in • Prepregs in roving form are also available for filament winding purposes. • Prepregs are generally used for hand lay-up, roll wrapping, compression molding, and

automatic lay-up processes. • prepregs are cured in the presence of pressure and temperature to obtain the final

product. • Process time for thermoset prepreg ( up to 8 hours), of thermoplastic (minutes)

Prepregs

Especial classes of fiber forms

Preforms (e.g. braiding and filament winding)

Suction

Preforms


Molding Compound • Molding compounds are made of short or long fibers impregnated with resins • In general, hey are used for compression molding and injection molding processes

Sheet Molding Compound (SMC) • Roughly speaking (similar to a prepreg). So it is a sheet preimpregnated with resin

but it has long and short fibers • primarily consists of polyester or vinylester resin, chopped glass fibers, inorganic

fillers (30% by weight short glass fibers). At 50 to 60% the system is called HMC • low-cost technology and used for high-volume production of composite

components requiring moderate strength (most popular composite in automotive) • Come with various thicknesses (up to 6 mm), process time (1 to 4 minutes),

processes with temperature and pressure reduce cost, increase

dimensional stability, and reduce shrinkage

Cross linking

Prevent premature curing

SMC fabrication (the sheet not the product)

polyethylene film

• Carrier films help in packaging and handling and are removed before molding (making a part)

• Continuous and short fibers can be added

• A polyester-based SMC has to pass through a maturation period (1 to 7 days at 30C) before using in molding. This period allows the resin viscosity to increase to the levels needed for molding (very low viscosity doesn’t allow pressure distribution)

Common Types of SMCs

SMC-R, for randomly oriented short fibers. The weight percent of the fiber is written after R. For example, SMC-R25 has 25 wt% short fibers

SMC-CR (continuous unidirectional and random fibers). The percentage amounts of C and R are denoted after the letters C and R as SMCC30R20)

XMC (mixture of random short fibers with continuous fibers in an X pattern with an angle 5 to 7°


Thick Molding Compound (TMC)

• Thick molding compound (TMC) is a thicker form of SMC and can go up to 50mm • Random fibers are distributed in 3D

Bulk Molding Compound (BMC) or dough molding compound (DMC).

• Has a log or rope form • obtained by mixing the resin paste with fibers and then extruding • generally contains 15 to 20% fiber in a polyester or vinylester resin • Fibers length from 6 to 12 mm. • Lowe mechanical properties that SMC (lower fiber volume fraction, shorter fiber

length) than SMC composites.

Injection Moldable Compounds For composites, the process similar to pultrusion Used with thermoplastic and thermosets For rod-like structures


Honeycomb and Other Core Materials

• Cores are used for sandwich structures as cores between two thin high-strength facings. Used in aircraft, transportation, marine, etc.

• joined with facings using an adhesive strong • Cores increase the structure second moment of inertia (just like I-beam) • The sandwich construction provides the highest stiffness-to-weight ratio and

strength-to-weight ratio • Commonly core flat sheet comes in a 4x8ftsize having a thickness of 0.125 to 12 in • Made mostly by expansion or corrugation



Material selection

Important concepts of composites

Design for manufacturing

Design for Assembly (DFA)