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Textile Structural Composites. Yiping Qiu College of Textiles Donghua University Spring, 2006. Reading Assignment. Textbook chapter 1 General Information. High-Performance Composites: An Overview, High-Performance Composites , 7-19, 2003 Sourcebook.

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Textile structural composites

Textile Structural Composites

Yiping Qiu

College of Textiles

Donghua University

Spring, 2006


Reading assignment

Reading Assignment

  • Textbook chapter 1 General Information.

  • High-Performance Composites: An Overview, High-PerformanceComposites, 7-19, 2003 Sourcebook.

  • FRP Materials, Manufacturing Methods and Markets, Composites Technology, Vol. 6(3) 6-20, 2000.


Expectations

Expectations

  • At the conclusion of this section, you should be able to:

    • Describe the advantages and disadvantages of fiber reinforced composite materials vs. other materials

    • Describe the major applications of fiber reinforced composites

    • Classification of composites


Introduction

Introduction

  • What is a composite material?

    • Two or more phases with different properties

  • Why composite materials?

    • Synergy

  • History

  • Current Status


Introduction1

Introduction

  • Applications

    • Automotive

    • Marine

    • Civil engineering

    • Space, aircraft and military

    • Sports


Applications in plane

Applications in plane


Fiber reinforced composite materials

Fiber reinforced composite materials

  • Classifications according to:

    • Matrices

      • Polymer

        • Thermoplastic

        • Thermoset

      • Metal

      • Ceramic

      • Others


Fiber reinforced composite materials1

Fiber reinforced composite materials

  • Classifications

    • Fibers

      • Length

        • short fiber reinforced

        • continuous fiber reinforced

      • Composition

        • Single fiber type

        • Hybrid

    • Mechanical properties

      • Conventional

      • Flexible


Fiber reinforced composite materials2

Fiber reinforced composite materials

  • Advantages

    • High strength to weight ratio

    • High stiffness to weight ratio

    • High fatigue resistance

    • No catastrophic failure

    • Low thermal expansion in fiber oriented directions

    • Resistance to chemicals and environmental factors


Textile structural composites

Comparison of specific gravities

8

6

Specific gravity

(g/cc)

4

2

0

Steel

Al alloy

Ti alloy

Kevlar/epoxy

Carbon/epoxy

materials


Fiber reinforced composite materials3

Fiber reinforced composite materials

  • Disadvantages

    • Good properties in one direction and poor properties in other directions.

    • High cost due to expensive material and complicated fabrication processes.

    • Some are brittle, such as carbon fiber reinforced composites.

    • Not enough data for safety criteria.


Design of composite materials

Design of Composite Materials

  • Property Maps

  • Merit index


Design of composite materials1

Design of Composite Materials

  • Merit index

  • Example for tensile stiffness of a beam

    • However, for a given tensile sample, tensile stiffness has nothing to do with length or L = 1 may be assumed


Design of composite materials2

Design of Composite Materials

  • How about for torsion beams and bending plates? Lets make the derivation of these our first homework.


Major components for fiber reinforced composites

Major components for fiber-reinforced composites

  • Reading assignment:

    • Textbook Chapter 2 Fibers and matrices

  • Fibers

    • Share major portion of the load

  • Matrix

    • To transfer stress between the fibers

    • To provide a barrier against an adverse environment

    • To protect the surface of the fibers from mechanical abrasion


Major components for fiber reinforced composites1

Major components for fiber reinforced composites

  • Coupling agents and coatings

    • to improve the adhesion between the fiber and the matrix

    • to protect fiber from being reacted with the matrix or other environmental conditions such as water moisture and reactive fluids.

  • Fillers and other additives:

    • to reduce the cost,

    • to increase stiffness,

    • to reduce shrinkage,

    • to control viscosity,

    • to produce smoother surface.


Materials for fiber reinforced composites

Materials for fiber reinforced composites

Mainly two components:

  • Fibers

  • Matrices


Materials for fiber reinforced composites1

Materials for fiber reinforced composites

  • Fibers

    • Influences:

      • Specific gravity,

      • Tensile and compressive strength and modulus,

      • Fatigue properties,

      • Electrical and thermal properties,

      • Cost.


Materials for fiber reinforced composites2

Materials for fiber reinforced composites

  • Fibers

    • Fibers used in composites

      • Polymeric fibers such as

        • PE (Spectra 900, 1000)

        • PPTA: Poly(para-phenylene terephthalamide) (Kevlar 29, 49, 149, 981, Twaron)

        • Polyester (Vectran or Vectra)

        • PBZT: Poly(p-phenylene benzobisthiozol)


Materials for fiber reinforced composites3

Materials for fiber reinforced composites

  • Fibers

    • Inorganic fibers:

      • Glass fibers: S-glass and E-glass

      • Carbon or graphite fibers: from PAN and Pitch

      • Ceramic fibers: Boron, SiC, Al2O3

      • Metal fibers: steel, alloys of W, Ti, Ni, Mo etc. (high melting temperature metal fibers)


Materials for fiber reinforced composites4

Materials for fiber reinforced composites

  • Most frequently used fibers

    • Glass

    • Carbon/graphite

    • PPTA (Kevlar, etc.)

    • Polyethylene (Spectra)

    • Polyester (Vectra)


Materials for fiber reinforced composites5

Materials for fiber reinforced composites

  • Carbon fibers

    • Manufacturing processes

    • Structure and properties


Materials for fiber reinforced composites6

Materials for fiber reinforced composites

  • Carbon fibers

    • Manufacturing processes

      • Thermal decomposition of fibrous organic precursors:

        • PAN and Rayon

        • Extrusion of pitch fibers


Materials for fiber reinforced composites7

Materials for fiber reinforced composites

  • Carbon fiber manufacturing processes

    • Thermal decomposition of fibrous organic precursors

    • Rayon fibers

      • Rayon based carbon fibers

        • Stabilization at 400°C in O2, depolymerization & aromatization

        • Carbonization at 400-700°C in an inert atmosphere

        • Stretch and graphitization at 700-2800°C (improve orientation and increase crystallinity by 30-50%)


Materials for fiber reinforced composites8

Materials for fiber reinforced composites

  • Carbon fiber manufacturing processes

    • Thermal decomposition of fibrous organic precursors

      • PAN (polyarylonitrile) based carbon fibers

        • PAN fibers (CH2-CH(CN))

          • Stabilization at 200-300°C in O2, depolymerization & aromatization, converting thermoplastic PAN to a nonplastic cyclic or ladder compound (CN groups combined and CH2 groups oxidized)

          • Carbonization at 1000-1500°C in an inert atmosphere to get rid of noncarbon elements (O and N) but the molecular orientation is still poor.

          • Stretch and graphitization at >1800°C, formation of turbostratic structure


Materials for fiber reinforced composites9

Materials for fiber reinforced composites

  • Pitch based carbon fibers

    • pitch - high molecular weight byproduct of distillation of petroleum

    • heated >350°C, condensation reaction, formation of mesophase (LC)

    • melt spinning into pitch fibers

    • conversion into graphite fibers at ~2000°C


Materials for fiber reinforced composites10

Materials for fiber reinforced composites

  • Carbon fibers

    • Advantages

      • High strength

      • Higher modulus

      • Nonreactive

        • Resistance to corrosion

        • High heat resistance

        • high tensile strength at elevated temperature

      • Low density


Materials for fiber reinforced composites11

Materials for fiber reinforced composites

  • Carbon fibers

    • Disadvantages

      • High cost

      • Brittle


Materials for fiber reinforced composites12

Materials for fiber reinforced composites

  • Carbon fibers

    • Other interesting properties

      • Lubricating properties

      • Electrical conductivity

      • Thermal conductivity

      • Low to negative thermal expansion coefficient


Materials for fiber reinforced composites13

Materials for fiber reinforced composites

  • Carbon fibers

    • heat treatment below 1700°C

      • less crystalline

      • and lower modulus (<365 GPa)

  • Graphite fibers

    • heat treatment above 1700°C

      • More crystalline (~80%) and

      • higher modulus (>365GPa)


Materials for fiber reinforced composites14

Materials for fiber reinforced composites

  • Glass fibers

    • Compositions and properties

    • Advantages and disadvantages


Materials for fiber reinforced composites15

Materials for fiber reinforced composites

  • Glass fibers

    • Compositions and Structures

      • Mainly SiO2 +oxides of Ca, B, Na, Fe, Al

      • Highly cross-linked polymer

        • Noncrystaline

        • No orientation

      • Si and O form tetrahedra with Si centered and O at the corners forming a rigid network

      • Addition of Ca, Na, & K with low valency breaks up the network by forming ionic bonds with O   strength and modulus


Microscopic view of glass fiber

Microscopic view of glass fiber

Cross polar

First order red plate


Materials for fiber reinforced composites16

Materials for fiber reinforced composites

  • Glass fibers

    • Types and Properties

      • E-glass (for electric)

        • draws well

        • good strength & stiffness

        • good electrical and weathering properties


Materials for fiber reinforced composites17

Materials for fiber reinforced composites

  • Glass fibers

    • Types and Properties

      • C-glass (for corrosion)

        • good resistance to corrosion

        • low strength


Materials for fiber reinforced composites18

Materials for fiber reinforced composites

  • Glass fibers

    • Types and Properties

      • S-glass (for strength)

        • high strength & modulus

        • high temperature resistance

        • more expensive than E


Materials for fiber reinforced composites19

Materials for fiber reinforced composites

  • Properties of Glass fibers


Materials for fiber reinforced composites20

Materials for fiber reinforced composites

  • Glass fibers

    • Production

      • Melt spinning


Materials for fiber reinforced composites21

Materials for fiber reinforced composites

  • Glass fibers

    • sizing:

      • purposes

        • protest surface

        • bond fibers together

        • anti-static

        • improve interfacial bonding

      • Necessary constituents

        • a film-forming polymer to provide protecting

          • e.g. polyvinyl acetate

        • a lubricant

        • a coupling agent: e.g. organosilane


Materials for fiber reinforced composites22

Materials for fiber reinforced composites

  • Glass fibers

    • Advantages

      • high strength

      • same strength and modulus in transverse direction as in longitudinal direction

      • low cost


Materials for fiber reinforced composites23

Materials for fiber reinforced composites

  • Glass fibers

    • disadvantages

      • relatively low modulus

      • high specific density (2.62 g/cc)

      • moisture sensitive


Materials for fiber reinforced composites24

Materials for fiber reinforced composites

  • Kevlar fibers

    • Structure

      • Polyamide with benzene rings between amide groups

      • Liquid crystalline

      • Planar array and pleated system


Materials for fiber reinforced composites25

Materials for fiber reinforced composites

  • Kevlar fibers

    • Types

      • Kevlar 29, E = 50 GPa

      • Kevlar 49, E = 125 GPa

      • Kevlar 149, E = 185 GPa


Materials for fiber reinforced composites26

Materials for fiber reinforced composites

  • Kevlar fibers

    • Advantages

      • high strength & modulus

      • low specific density (1.47g/cc)

      • relatively high temperature resistance


Materials for fiber reinforced composites27

Materials for fiber reinforced composites

  • Kevlar fibers

    • Disadvantages

      • Easy to fibrillate

      • poor transverse properties

      • susceptible to abrasion


Materials for fiber reinforced composites28

Materials for fiber reinforced composites

  • Spectra fibers

    • Structure: (CH2CH2)n

      • Linear polymer - easy to pack

      • No reactive groups

    • Advantages

      • high strength and modulus

      • low specific gravity

      • excellent resistance to chemicals

      • nontoxic for biomedical applications


Materials for fiber reinforced composites29

Materials for fiber reinforced composites

  • Spectra fibers

    • Disadvantages

      • poor adhesion to matrix

      • high creep

      • low melting temperature


Materials for fiber reinforced composites30

Materials for fiber reinforced composites

  • Other fibers

    • SiC and Boron

      • Production

        • Chemical Vapor Deposition (CVD)

          • Monofilament

          • Carbon or Tungsten core heated by passing an electrical current

          • Gaseous carbon containing silane


Materials for fiber reinforced composites31

Materials for fiber reinforced composites

  • SiC

    • Production

      • Polycarbosilane (PCS)

        • Multi-filaments

        • polymerization process to produce precursor

        • PCS pyrolised at 1300ºC

      • Whiskers

        • Small defect free single crystal


Materials for fiber reinforced composites32

Materials for fiber reinforced composites

  • Particulate

    • small aspect ratio

    • high strength and modulus

    • mostly cheap


Materials for fiber reinforced composites33

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Compressive strength

    • Fiber fracture and flexibility

    • Statistical treatment of fiber strength


Materials for fiber reinforced composites34

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Compressive strength

      • (Mainly) Euler Buckling


Materials for fiber reinforced composites35

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Factors determining compressive strength

      • Matrix material

      • Fiber diameter or aspect ratio (L/d)

      • fiber properties

        • carbon & glass >> Kevlar


Materials for fiber reinforced composites36

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Fiber fracture

      • Mostly brittle

        • e.g. Carbon, glass, SiC

      • Some ductile

        • e.g. Kevlar, Spectra

      • Fibrillation

        • e.g. Kevlar


Materials for fiber reinforced composites37

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Fiber flexibility

      • How easy to be bent

        • Moment required to bend a round fiber:

E = Young’s Modulus

d = fiber diameter

 = curvature


Materials for fiber reinforced composites38

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Fiber failure in bending

      • Stress on surface

        • Tensile stress:

E = Young’s Modulus

d = fiber diameter

 = curvature


Materials for fiber reinforced composites39

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Fiber failure in bending

      • Stress on surface

        • Maximum curvature

* = fiber tensile strength


Materials for fiber reinforced composites40

Materials for fiber reinforced composites

  • The strength of reinforcements

    • Fiber failure in bending

      • When bent, many fibers fail in compression

      • Kevlar forms kink bands


Materials for fiber reinforced composites41

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Brittle materials: failure caused by random flaw

      • don’t have a well defined tensile strength

      • presence of a flaw population

    • Statistical treatment of fiber strength

      • Peirce (1928): divide a fiber into incremental lengths


Materials for fiber reinforced composites42

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Peirce’s experiment

      • Hypothesis:

        • The longer the fiber length, the higher the probability that it will contain a serious flaw.

        • Longer fibers have lower mean tensile strength.

        • Longer fibers have smaller variation in tensile strength.


Materials for fiber reinforced composites43

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Peirce’s experiment

      • Experimental verification:


Materials for fiber reinforced composites44

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weakest Link Theory (WLT)

      • define n = No. of flaws per unit length causing failure under stress .

      • For the first element, the probability of failure

The probability for the fiber to survive


Materials for fiber reinforced composites45

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weakest Link Theory (WLT)

      • If the length of each segment is very small, then Pfi are all very small,

        • Therefore (1-Pfi)  exp(-Pfi)

      • The probability for the fiber to survive


Materials for fiber reinforced composites46

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weibull distribution of fiber strength

      • Weibull’s assumption:

m = Weibull shape parameter (modulus).

0 = Weibull scale parameter, characteristic strength.

L0 = Arbitrary reference length.


Materials for fiber reinforced composites47

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weibull distribution of fiber strength

      • Thus


Materials for fiber reinforced composites48

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weibull distribution of fiber strength

      • Discussion:

        • Shape parameter ranges 2-20 for ceramic and many other fibers.

        • The higher the shape parameter, the smaller the variation.

        • When <0, the probability of failure is small if m is large.

        • When 0, failure occurs.

        • Weibull distribution is used in bundle theory to predict fiber bundle and composite strength.


Materials for fiber reinforced composites49

Materials for fiber reinforced composites

  • Statistical treatment of fiber strength

    • Weibull distribution of fiber strength

      • Plot of fiber strength or failure strain data

        • let


Statistical treatment of fiber strength

Statistical treatment of fiber strength

  • Example

    • Estimate number of fibers fail at a gage length twice as much as the gage length in single fiber test

    • L/L0 = 2


Matrices

Matrices

  • Additional reading assignment:

    • Jones, F.R., Handbook of Polymer-Fiber Composites, sections:

      • 2.4-2.6, 2.9, 2.10, 2.12.


Matrices1

Matrices

  • Polymer

  • Metal

  • Ceramic


Matrices2

Matrices

  • Polymer

    • Thermosetting resins

      • Epoxy

      • Unsatulated polyester

      • Vinyl ester

      • high temperature:

        • Polyimides

        • Phenolic resins


Matrices3

Matrices

  • Polymer

    • Target net resin properties


Epoxy resins

Epoxy resins

  • Starting materials:

    • Low molecular weight organic compounds containing epoxide groups


Epoxy resins1

Epoxy Resins

  • Types of epoxy resins


Epoxy resins2

Epoxy resins

  • Types of epoxy resin

    • bifuctional: diglycidyl ether of bisphenol A

      • a distribution of monomers  n is fractional:

      • effect of n

        •  molecular weight  viscosity  curing temp.

        •  distance between crosslinks  Tg &  ductility

        •  -OH  moisture absorption


Epoxy resins3

Epoxy resins

  • Types of epoxy resin (cont.)

    • Trifunctional (glycidyl amines)

    • Tetrafunctional

      • higher functionality

      • potentially higher crosslink densities

      • higher Tg

      • Less -OH groups  moisture absorption


Epoxy resins4

Epoxy resins

  • Curing

    • Copolymerization:

      • A hardener required: e.g. DDS, DICY

      • Hardeners have two active “H” atoms to add to the epoxy groups of neighboring epoxy molecules, usually from -NH2

      • Formation of -OH groups: moisture sensitive

      • Addition polymerization: No small molecules formed  no volatile formation

      • Stoichiometric concentration used, phr: part per hundred (parts) of resin


Epoxy resin

Epoxy resin

  • Major ingredients: epoxy resin and curing agent


Epoxy resin1

Epoxy resin

  • Chemical reactions


Epoxy resin2

Epoxy resin

  • Chemical reactions


Epoxy resins5

Epoxy resins

  • Curing

    • Homopolymerization:

      • Addition polymerization: a catalyst or initiator required: eg. Tertiary amines and BF3 compounds

      • Less -OH groups formed

      • Typical properties of addition polymers

    • Combination of catalyst with hardeners


Epoxy resins6

Epoxy Resins

  • Reaction of homopolymerization


Epoxy resins7

Epoxy resins

  • Epoxy resins

    • Mechanical and thermomechanical properties

      • Effect of curing agent on mechanical properties

      • Heat distortion temperature (HDT)

        • measured as temperature at which deflection of 0.25 mm of 100 mm long bar under 0.455 MPa fiber stress occurs.

        • related but  Tg

      • Moisture absorption: 1% decrease Tg by 20ºK


Polyimides

Polyimides

  • Largest class of high temperature polymers in composites

    • Types

      • PMR (polymerization of monomeric reactants)

        • polyimides are insoluble and infusible.

        • in situ condensation polymerization of monomers in a solvent

        • 2 stage process:

          • first stage to form imidized prepolymer of oligomer and volatile by-products removed using autoclave or vacuum oven.

          • Second stage: prepolymer is crosslinked via reaction of the norbornene end cap under high pressure and temperature (316ºC and 200 psi)


Polyimides1

Polyimides

  • Types

    • bis-imides (derived from monomers with 2 preformed imide groups).

      • Typical BMI (bismaleimides)

      • Used for lower temperature range ~ 200ºC


Polyimides2

Polyimides

  • Properties (show tables)


Polyimides3

Polyimides

  • Advantages:

    • Heat resistant

  • Drawbacks:

    • toxicity of constituent chemicals (e.g. MDA)

    • microcracking of fibers on thermal cycling

    • high processing temperature

  • Typical Applications

    • Engine parts in aerospace industry


Phenolic resins

Phenolic resins

  • Prepared through condensation polymerization between phenol and formaldehyde.

  • Large quantity of Water generated (up to 25%) leading to high void content


Phenolic resins1

Phenolic resins

  • Advantages:

    • High temperature stability

    • Chemical resistance

    • Flame retardant

    • Good electrical properties

  • Typical applications

    • Offshore structures

    • Civil engineering

    • Marine

    • Auto parts: water pumps, brake components

    • pan handles and electric meter cases


Time temperature transformation diagrams for thermosets resins

Time-temperature-transformation diagrams for thermosets resins

  • Additional reading assignment:

    • reserved: Gillham, J.K., Formation and Properties of Thermosetting and High Tg Polymeric Materials, Polymer Engineering and Science, 26, 1986, p1429-1431


Time temperature transformation diagrams for thermosets resins1

Time-temperature-transformation diagrams for thermosets resins


Time temperature transformation diagrams for thermosets resins2

Time-temperature-transformation diagrams for thermosets resins

  • Important concepts

    • Gelation

      • formation of an infinite network

      • sol and gel coexist

    • Vitrification

      • Tg rises to isothermal temperature of cure

      • Tcure > Tg, rubbery material

      • Tcure < Tg, glassy material

      • After vitrification, conversion of monomer almost ceases.


Time temperature transformation diagrams for thermosets resins3

Time-temperature-transformation diagrams for thermosets resins

  • Important concepts

    • Devitrification

      • Tg decreases through isothermal temperature of cure due to degradation

      • degradation leads to decrosslink and formation of plasticizing materials

    • Char or vitrification

      • due to increase of crosslink and volatilization of low molecular weight plasticizing materials


Time temperature transformation diagrams for thermosets resins4

Time-temperature-transformation diagrams for thermosets resins

  • Important concepts

    • Three critical temperatures:

      • Tg - Tg of cured system

      • gelTg - Tg of gel

      • Tgo - Tg of reactants


Time temperature transformation diagrams for thermosets resins5

Time-temperature-transformation diagrams for thermosets resins

  • Discussion

    • Ungelled glassy state is good for commercial molding compounds

      • Tgo > Tprocessing, processed as solid

      • Tgo < Tprocessing, processed as liquid

    • Store temperature < gelTg to avoid gelation

    • Resin fully cured when Tg = Tg

    • Tg > Tcure about 40ºC

    • Full cure is achieved most readily by cure at T > Tg and slowly at T < Tg.


Unsaturated polyester

Unsaturated polyester

  • Reading assignment

  • Mallick, P.K., Fiber Reinforced Composites . Materials, Manufacturing and Design, pp56-64.

  • Resin:

    • Products of condensation polymerization of diacids and diols

      • e.g. Maleic anhydride and ethylene glycol

    • Strictly alternating polymers of the type A-B-A-B-A-B

    • At least one of the monomers is ethylenically unsaturated


Unsaturated polyester1

Unsaturated polyester


Unsaturated polyester2

Unsaturated polyester


Unsaturated polyester3

Unsaturated polyester

  • Cross-linking agent

    • Reactive solvent of the resin: e.g. styrene

    • Addition polymerization with the resin molecules: initiator needed, e.g. peroxide

    • Application of heat to decompose the initiator to start addition polymerization

    • an accelerator may be added to increase the decomposition rate of the initiator.


Unsaturated polyester4

Unsaturated polyester


Unsaturated polyester5

Unsaturated polyester

  • Factors to control properties

    • Cross-linking density:

      • addition of saturated diacids as part of the monomer for the resin: e.g phthalic anhydrid, isophthalic acid and terephthalic acid

      • as ratio of saturated acids to unsaturated acids increases, strength and elongation increase while HDT decreases


Unsaturated polyester6

Unsaturated polyester

  • Factors controlling properties

    • Type of acids

      • Terephthalic acids provide higher HDT than the other two acids due to better packing of molecules

      • nonaromatic acid: adipic acid HOOC(CH2)4COOH, lowers stiffness

    • Resin microstructure:

      • local extremely high density of cross-links.

    • Type of diols

      • larger diol monomer: diethylene glycol

      • bulky side groups


Unsaturated polyester7

Unsaturated polyester

  • Factors to control properties

    • Type of crosslinking agent

      • amount of styrene: more styrene increases the distance of the space of neighboring polyester molecules  lower modulus

      • Excessive styrene: self-polymerization  formation of polystyrene  polystyrene-like properties


Unsaturated polyester8

Unsaturated polyester

  • Advantages

    • Low viscosity

    • Fast cure

    • Low cost

  • Disadvantages

    • lower properties than epoxy

    • large mold shrinkage  sink marks

      • an incompatible thermoplastic mixed into the resin to form a dispersed phase in the resin  “low profile” system


Vinyl ester

Vinyl ester

  • Resin:

    • Products of addition polymerization of epoxy resin and an unsaturated carboxylic acid (vinyl)

    • unsaturated C=C bonds are at the end of a vinyl ester molecule  fewer cross-links  more flexible

  • Cross-linking agent

    • The polymer is dissolved in styrene

    • Addition polymerization to form cross-links

    • Formation of a gigantic molecule

    • Similar curing reaction as unsaturated polyester resin


Vinyl ester1

Vinyl ester


Vinyl ester2

Vinyl ester


Vinyl ester3

Vinyl ester

  • Advantages

    • epoxy-like:

      • excellent chemical resistance

      • high tensile strength

    • polyester-like:

      • Low viscosity

      • Fast curing

      • less expensive

    • good adhesion to glass fibers due to existence of -OH

  • Disadvantages:

    • Large volumetric shrinkage (5 – 10 %)


Vinyl ester4

Vinyl ester


Advantages of thermosetting resins

Advantages ofthermosetting resins

  • High strength and modulus.

  • Less creep and stress relaxation

  • Good resistance to heat and chemicals

  • Better wet-out between fibers and matrix due to low viscosity before cross-linking


Disadvantages of thermosetting resins

Disadvantages of thermosetting resins

  • Limited storage life

  • Long time to cure

  • Low strain to failure

  • Low impact resistance

  • Large shrinkage on curing


Thermoplastic matrices

Thermoplastic matrices

  • Reading assignment:

    • Mallick, P.K., Fiber Reinforced Composites . Materials, Manufacturing and Design, section 2.4 pp 64-69.

  • Types:

    • Conventional: no chemical reaction during processing

      • Semi-crystalline

      • Liquid crystal

      • Amorphous

    • Pseudothermoplastics: molecular weight increase and expelling volatiles


Thermoplastic matrices1

Thermoplastic matrices

  • examples:

    • Conventional

      • Nylon

      • Polyethylene

      • Polypropylene

      • Polycarbonate

      • Polyester

      • PMMA


Thermoplastic matrices2

Thermoplastic matrices

  • examples:

    • Advanced (e.g.)


Thermoplastic matrices3

Thermoplastic matrices

  • examples:

    • Advanced (e.g.)

      • Polyimide


Thermoplastic matrices4

Thermoplastic matrices


Thermoplastic matrices5

Thermoplastic matrices

  • Main descriptors:

    • Linear

    • Repeatedly meltable

  • Properties and advantages of thermoplastic matrices

    • High failure strain

    • High impact resistance

    • Unlimited storage life at room temperature

    • Short fabrication time

    • Postformability (thermoforming)

    • Ease of repair by welding, solvent bonding

    • Ease of handling (no tackiness)


Thermoplastic matrices6

Thermoplastic matrices


Disadvantages of thermoplastic matrices

Disadvantages of thermoplastic matrices

  • High melt or solution viscosity (high MW)

  • Difficult to mix them with fibers

  • Relatively low creep resistance

  • Low heat resistance for conventional thermoplastics


Metal matrices

Metal Matrices

  • Examples

    • Al, Ti, Mg, Cu and Super alloys

  • Reinforcements:

    • Fibers: boron, carbon, metal wires

    • Whiskers

    • Particulate


Metal matrices1

Metal Matrices

  • Fiber matrix interaction

    • Fiber and matrix mutually nonreactive and insoluble

    • Fiber and matrix mutually nonreactive but soluble

    • Fiber and matrix react to form compounds at interface


Metal matrices2

Metal Matrices

  • Advantage of metal matrix composites (MMC)

    • Versus unreinforced metals

      • higher strength to density ratio

      • better properties at elevated temperature

      • lower coefficient of thermal expansion

      • better wear characteristics

      • better creep performance


Metal matrices3

Metal Matrices

  • Advantage of MMC

    • Versus polymeric matrix

      • better properties at elevated temperature

      • higher transverse stiffness and strength

      • moisture insensitivity

      • higher electrical and thermal conductivity

      • better radiation resistance

      • less outgassing contamination


Metal matrices4

Metal Matrices

  • Disadvantage of MMC

    • higher cost

      • high processing temperature

      • relatively immature technology

      • complex and expensive fabrication methods with continuous fiber reinforcements

    • high specific gravity compared with polymer

    • corrosion at fiber matrix interface (high affiliation to oxygen)

    • limited service experience


Ceramic matrices

Ceramic Matrices

  • Glass ceramics

    • glass forming oxides, e.g. Borosilicates and aluminosilicates

    • semi-crystalline with lower softening temperature

  • Conventional ceramics

    • SiC, Si3N4, Al2O3, ZrO2

    • fully crystalline

  • Cement and concrete

  • Carbon/carbon


Ceramic matrices1

Ceramic Matrices

  • Increased toughness through deflected crack propagation on fiber/matrix interface.

  • Example: Carbon/carbon composites


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