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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
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
slide10

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 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 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 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 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 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 %)
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 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)
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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