Lecture 8: Raw materials for part fabrication 4: Resin 2

Crosslinking

Chemical process joining separate polymer chains

What does crosslinking cause in a resin / matrix?

-Solidification

-Increase in strength / stiffness

-Increase in Tg and Tmelting

Thermoset matrix / resin materials characteristics

-Uncured: low molecular weight

-Crosslinking (improves strength / stiffness, remember thermosets harden when heated)

Thermoset matrix / resin materials disadvantages

-mixing of chemicals required

-poor toughness

-limited shelf life

-longer cure times

-unable to reshape material after cure

Thermoplastic matrix / resin materials characteristics

-Represents 80% of plastic and composite market place

-No change in molecular weight

-No cross-links

-Fabrication time less

Thermoplastics matrix / resin materials disadvantages

-Difficult fiber wet-out

What resins dominate composites, and how much of the market is not made up of them?

-Polyester and Epoxy resins

-Specialty resins make up 20% of composite market

List some specialty thermoset resins

-Vinyl Esters

-Phenolics

-Carbon Matrix

-Polyimides

-Cyanate Esters

-Polyurethanes

-Dicyclopentadiene (DCPD)

Vinyl Esters

-Thermoset

-Cheaper than epoxies

-Toughness / corrosion properties better then polyesters but not as good as epoxies

-Used for pipes and tanks for chemical industry

Phenolics

-Thermoset

-Excellent flame / chlorinated solvent performance

-High crosslink density, strong but brittle / high shrinkage (fillers mediate this)

-Used for airplane interiors / rocket exit nozzles

Carbon Matrix

-Thermoset

-Made when carbon-rich resin (commonly phenolics) is converted into carbon

-High thermal stability (unlike phenolics, little heat abrasion)

-Used for rocket nose cones / gas turbine engines

Polymides

-Thermoset or Thermoplastics

-Cheaper than carbon-carbon composites

-Better high-temperature and high electrical resistance capability

-Used as aircraft engine blades and firewalls on fighter planes

Cyanete Esters

-Thermoset

-Great dielectric loss

-Low moisture absorption

-Used in radomes and advanced stealth components

Polyurethanes

-Thermoset

-High toughness

-Wide choice of formulations

-Used for automotive body parts

Dicyclopentadience (DCPD)

-Thermoset

-Corrosion resistant

-Helps self-heal composite materials

What are some thermoplastic resins?

-Polyimides

-Polyetheretherketone (PEEK)

-Polysulfones

-Liquid Crystal Polymers

-Fluropolymers

Poletheretherketone (PEEK)

-Possibly most widely used thermoplastic

-Semi-crystalline material

-High rigidity, strength, thermal stability

-Easy to process

-Used in aerospace industry

What groups are composites seperated into?

-Resin types: thermosets vs thermoplastics

-Engineering vs Advanced composite materials

Major applications of engineering thermosets

Automobiles and boats

Major applications of Engineering thermoplastics

-Strengthen plastic parts

-Valves and football helmets

Major applications of Advanced thermosets

-Helicopters and airplanes

Major applications of advanced thermoplastics

-submarines and tanks

Ceramic matrix composites properties

-Used in high temperature (up to 3000 degrees F) areas where structural strength is less important and high stiffness desired

-Brittle, therefore reinforcements used to increase toughness

Ceramic matrix applications

-Used in heat shields, wing leading edges and nose tips

Common matrix composites

Alumina, borosilicate, magnesium oxide, boron nitride

Metal matrix properties

-Higher strength / stiffness over non-reinforced metals

-Higher temperature stability then polymer matrix

-Has qualities of metal like electrical / thermal conductivity

-Can be processed by conventional metal methods if the reinforcements are discontinuous

Metal matrix applications

Pistons in cars, structural rods / antennas in aerospace, golf clubs

Common metal matrixes

Aluminum, titanium, magnesium, copper, nickel, and various alloys

Polymer matrix advantages compared to ceramic / metal

-Easier molding and fiber wet out

-Cheaper

-Lighter

Polymer matrix disadvantages compared to ceramic / metal

-Lower thermal stability

-Lower stiffness

-Lower hardness