Composite MaterialsComposite Materials

Ahmed W. MoustafaAhmed W. Moustafa

Lecture (1)Lecture (1)

Composite MaterialComposite Material

Two inherently different Two inherently different materials that when materials that when combined together produce a combined together produce a material with properties that material with properties that exceed the constituent exceed the constituent materials.materials.

Composite Material Composite Material DefinedDefined

A materials system composed of two or A materials system composed of two or more physically distinct phases whose more physically distinct phases whose combination produces aggregate combination produces aggregate properties that are different from those properties that are different from those of its constituents of its constituents

Composite Material Composite Material DefinedDefined

Examples:Examples:– Cemented carbides (WC with Co binder)Cemented carbides (WC with Co binder)– Plastic molding compounds containing fillers Plastic molding compounds containing fillers – Rubber mixed with carbon blackRubber mixed with carbon black– Wood (a natural composite as distinguished Wood (a natural composite as distinguished

from a synthesized composite) from a synthesized composite)

Why Composites are Why Composites are ImportantImportant Composites can be very strong and stiff, yet Composites can be very strong and stiff, yet

very light in weight, so ratios of very light in weight, so ratios of strength‑to‑weight and stiffness‑to‑weight are strength‑to‑weight and stiffness‑to‑weight are several times greater than steel or aluminum several times greater than steel or aluminum

Fatigue properties are generally better than for Fatigue properties are generally better than for common engineering metals common engineering metals

Toughness is often greater too Toughness is often greater too Composites can be designed that do not Composites can be designed that do not

corrode like steel corrode like steel Possible to achieve combinations of properties Possible to achieve combinations of properties

not attainable with metals, ceramics, or not attainable with metals, ceramics, or polymers alone polymers alone

Disadvantages and Disadvantages and LimitationsLimitations Properties of many important composites are Properties of many important composites are

anisotropic ‑ the properties differ depending on anisotropic ‑ the properties differ depending on the direction in which they are measured – this the direction in which they are measured – this may be an advantage or a disadvantagemay be an advantage or a disadvantage

Many of the polymer‑based composites are Many of the polymer‑based composites are subject to attack by chemicals or solvents, just subject to attack by chemicals or solvents, just as the polymers themselves are susceptible to as the polymers themselves are susceptible to attackattack

Composite materials are generally expensiveComposite materials are generally expensive Manufacturing methods for shaping composite Manufacturing methods for shaping composite

materials are often slow and costly materials are often slow and costly

Classification of Classification of Composite MaterialsComposite Materials1.1. Traditional compositesTraditional composites – composite – composite

materials that occur in nature or have been materials that occur in nature or have been produced by civilizations for many years produced by civilizations for many years – Examples: wood, concrete, asphaltExamples: wood, concrete, asphalt

2.2. Synthetic compositesSynthetic composites - modern material - modern material systems normally associated with the systems normally associated with the manufacturing industries, in which the manufacturing industries, in which the components are first produced separately components are first produced separately and then combined in a controlled way to and then combined in a controlled way to achieve the desired structure, properties, achieve the desired structure, properties, and part geometry and part geometry

Components in a Components in a Composite MaterialComposite Material Nearly all composite materials consist Nearly all composite materials consist

of two phases: of two phases: 1.1. Primary phase - forms the Primary phase - forms the matrixmatrix within within

which the secondary phase is imbedded which the secondary phase is imbedded

2.2. Secondary phase - imbedded phase Secondary phase - imbedded phase sometimes referred to as a sometimes referred to as a reinforcingreinforcing agentagent, because it usually serves to , because it usually serves to strengthen the composite strengthen the composite The reinforcing phase may be in the form of The reinforcing phase may be in the form of

fibers, particles, or various other geometriesfibers, particles, or various other geometries

Functions of the Functions of the Matrix Material Matrix Material (Primary Phase)(Primary Phase) Provides the bulk form of the part or Provides the bulk form of the part or

product made of the composite material product made of the composite material Holds the imbedded phase in place, Holds the imbedded phase in place,

usually enclosing and often concealing it usually enclosing and often concealing it When a load is applied, the matrix shares When a load is applied, the matrix shares

the load with the secondary phase, in the load with the secondary phase, in some cases deforming so that the stress is some cases deforming so that the stress is essentially born by the reinforcing agent essentially born by the reinforcing agent

Composites OfferComposites Offer

High StrengthHigh Strength Light WeightLight Weight Design FlexibilityDesign Flexibility Consolidation of PartsConsolidation of Parts Net Shape ManufacturingNet Shape Manufacturing

Fiber Reinforced Polymer Fiber Reinforced Polymer Matrix Matrix

MatrixMatrix •Transfer Load to Reinforcement•Temperature Resistance•Chemical Resistance

Reinforcement

•Tensile Properties•Stiffness•Impact Resistance

Design ObjectiveDesign Objective

Performance: Strength, Temperature, Performance: Strength, Temperature, StiffnessStiffnessManufacturing TechniquesManufacturing TechniquesLife Cycle ConsiderationsLife Cycle ConsiderationsCostCost

Matrix ConsiderationsMatrix Considerations

End Use TemperatureEnd Use TemperatureToughnessToughnessCosmetic IssuesCosmetic IssuesFlame RetardantFlame RetardantProcessing MethodProcessing MethodAdhesion Adhesion RequirementsRequirements

Matrix TypesMatrix Types

PolyesterPolyester  

Polyesters have good mechanical Polyesters have good mechanical properties, electrical properties and properties, electrical properties and chemical resistance. Polyesters are chemical resistance. Polyesters are amenable to multiple fabrication amenable to multiple fabrication techniques and are low cost.techniques and are low cost.  

Vinyl EstersVinyl Esters

Vinyl Esters are similar to polyester in Vinyl Esters are similar to polyester in performance. Vinyl esters have increased performance. Vinyl esters have increased resistance to corrosive environments as resistance to corrosive environments as well as a high degree of moisture well as a high degree of moisture resistance.resistance.

Matrix TypesMatrix Types

EpoxyEpoxy

Epoxies have improved strength and stiffness Epoxies have improved strength and stiffness properties over polyesters. Epoxies offer properties over polyesters. Epoxies offer excellent corrosion resistance and resistance excellent corrosion resistance and resistance to solvents and alkalis. Cure cycles are to solvents and alkalis. Cure cycles are usually longer than polyesters, however no usually longer than polyesters, however no by-products are produced.by-products are produced.  

Flexibility and improved performance is also Flexibility and improved performance is also achieved by the utilization of additives and achieved by the utilization of additives and fillers.fillers.

ReinforcementReinforcement Fiber TypeFiber TypeFiberglassFiberglassCarbonCarbonAramidAramid  

Textile Textile StructureStructureUnidirectionalUnidirectionalWovenWovenBraidBraid

FiberglassFiberglass

E-glass:E-glass: Alumina-calcium-borosilicate glassAlumina-calcium-borosilicate glass

(electrical applications)(electrical applications)

S-2 glass: Magnesuim aluminosilicate glass(reinforcements)

Glass offers good mechanical, electrical, and thermal properties at a relatively low cost.

E-glass S-2 glassDensity 2.56 g/cc 2.46 g/ccTensile Strength 390 ksi 620 ksiTensile Modulus 10.5 msi 13 msiElongation 4.8% 5.3%

AramidAramid Kevlar™ & Twaron™Kevlar™ & Twaron™  

Para aramid fiber characterized by high tensile strength Para aramid fiber characterized by high tensile strength and modulusand modulus  

Excellent Impact ResistanceExcellent Impact Resistance

Good Temperature ResistanceGood Temperature Resistance

Density 1.44 g/ccTensile Strength 400 ksiTensile Modulus 18 MsiElongation 2.5%

Carbon Carbon FiberFiber

PAN: Fiber made from Polyacrylonitrile PAN: Fiber made from Polyacrylonitrile precursor fiberprecursor fiber

  

High strength and stiffnessHigh strength and stiffness

Large variety of fiber types availableLarge variety of fiber types available

Standard Modulus Intermediate Modulus Density 1.79 g/cc 1.79 g/ccTensile Strength 600 ksi 800 ksiTensile Modulus 33 Msi 42 MsiElongation 1.8 % 1.8 %

Weight Weight ConsiderationsConsiderations

Aramid fibers are the lightestAramid fibers are the lightest

1.3-1.4 g/cc1.3-1.4 g/cc

CarbonCarbon

1.79 g/c1.79 g/c

  

Fiberglass is the heaviestFiberglass is the heaviest

2.4 g/cc2.4 g/cc

Strength ConsiderationsStrength Considerations

Carbon is the strongestCarbon is the strongest

600-800 ksi600-800 ksi

FiberglassFiberglass

400-600 ksi400-600 ksi

AramidsAramids

400 ksi400 ksi

Impact Impact ResistanceResistance

Kevlar is the toughestKevlar is the toughest

FiberglassFiberglass

CarbonCarbon

Stiffness Stiffness ConsiderationsConsiderations

Carbon is the stiffestCarbon is the stiffest

30-40 msi30-40 msi

AramidsAramids

14 msi14 msi

FiberglassFiberglass

10-13 msi10-13 msi

CostCost ConsiderationsConsiderations

Fiberglass is cost effectiveFiberglass is cost effective

$5.00-8.00/lb.$5.00-8.00/lb.

  

AramidsAramids

$20.00/lb$20.00/lb

  

CarbonCarbon

$30.00-$50.00/lb$30.00-$50.00/lb

Fabric Fabric StructuresStructures Woven:Woven: Series of Interlaced yarns at 90° to Series of Interlaced yarns at 90° to each othereach other

  

Knit:Knit: Series of Interlooped YarnsSeries of Interlooped Yarns

  

Braided:Braided: Series of Intertwined, Spiral YarnsSeries of Intertwined, Spiral Yarns

  

Nonwoven:Nonwoven: Oriented fibers either Oriented fibers either mechanically, mechanically, chemically, or chemically, or thermally bondedthermally bonded

Woven FabricsWoven Fabrics

Basic woven fabrics consists of two systems Basic woven fabrics consists of two systems of yarns interlaced at right angles to create of yarns interlaced at right angles to create a single layer with isotropic or biaxial a single layer with isotropic or biaxial properties.properties.

Physical Physical PropertiesProperties

Construction (ends & picks)Construction (ends & picks)WeightWeightThicknessThicknessWeave TypeWeave Type

Components of a Woven Components of a Woven FabricFabric

Basic Weave TypesBasic Weave Types

Plain Weave

Basic Weave Basic Weave TypesTypes

Satin 5HS

Basic Weave TypesBasic Weave Types2 x 2 Twill

Basic Weave TypesBasic Weave Types

Non-Crimp

BraidingBraiding

A braid consists of two sets of yarns, which are helically intertwined. The resulting structure is oriented to the longitudinal axis of the braid. This structure is imparted with a high level of conformability, relative low cost and ease of manufacture.

Braid StructureBraid Structure

Types of BraidsTypes of Braids

Triaxial YarnsTriaxial Yarns

• A system of longitudinal yarns can be introduced which are held in place by the braiding yarns

• These yarns will add dimensional stability, improve tensile properties, stiffness and compressive strength.

• Yarns can also be added to the core of the braid to form a solid braid.

ConclusionsConclusions

Composite materials offer endless design options.

Matrix, Fiber and Preform selections are critical in the design process.

Structures can be produced with specific properties to meet end use requirements.