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Book used to cover the manufacturing aspects
Composites Manufacturing: Materials, Product, and Process Engineering [CRC press], 2001 Sanjay Mazumdar (Author)
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
Raw Materials for Part Fabrication
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
Raw Materials for Part Fabrication
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.
Raw Materials for Part Fabrication
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)
Raw Materials for Part Fabrication
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 :
Raw Materials for Part Fabrication
Thermosets:
Raw Materials for Part Fabrication
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
Especial classes of fiber forms
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°
Especial classes of fiber forms
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
Raw Materials for Part Fabrication
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
Honeycomb and Other Core Materials
Honeycomb and Other Core Materials
Material selection
Important concepts of composites
Design for manufacturing
Design for Assembly (DFA)
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