composite technology and new...

Composite technology and new materials

AUTOMOTIVE DAY BRASIL, October 6, 2011

MSc. Guilherme Wolf LebrãoProfessor of Polymer Composite MaterialsMauá Engineering, CEUN - IMT

What is a composite?

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Multiphase material

Combined properties

There are many definitions for composite materials. In general, they are multiphase materials resulting from the balanced

combination of two or more different materials to produce improved final properties.

Multiphase material

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Classification according to reinforcement

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Why use composites?

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• Low density• Materials with special characteristics• Controlled mechanical and chemical

features• Resistant to fatigue • Transparent to electro-magnetic waves• Freedom of design• Low maintenance

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Comparison – Tensile Strength Limits

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Comparison – Stiffness

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ρ – Specific gravity (Density)σ – Tensile strength stress limit

Properties

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E – Elastic modulus* – Estimated

Who uses composites?

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Railroads

Aviation

Aerospace

Formula 1

Buses

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Data related to the composition of materials used in lightweight automotive vehicles during the period 2001-2008,

indicating a variation of percentage compositions less than 5%.

Composition of materials for lightweight vehicles

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MetalPolymersElastomersGlassOther

MetalPolymersElastomersGlassOther

Trends

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The method used to actively monitor a composite involves measuring the changes in the fiber’s electrical resistance to assess the location and size of a crack or delamination of laminated composites. The electric resistance is measured with a tension amplifier. The system uses the resulting data as a tool to solve inverse problems such as calculating the location and size of cracks.

Active monitoring

A tool to solve an inverse problem (response surface)

e1 e2 e3 e4

Electrodes

Delamination

Location Size

Measured electric resistance change

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Auxetic material

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From a practical standpoint, an auxetic material is one that gets thicker when under tension. An elastic fiber acts as the wire core, around which a very strong and stiff wire is coiled. When this wire is tensioned, the wire diameter is effectively increased. The auxetic material wires can be woven in such a way that they are reinforced, becoming thicker and stiffer when under an external impact that tends to stretch them.

The main feature of modern auto-regenerative materials is the presence of polymerization or catalytic agents in a polymer matrix. When physical, chemical or thermal action is applied, these agents close any cracks, usually by means of matrix polymerization.

Auto-regenerative

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Cluster

Shell

Core Shell

Nanotube

Buckyball (Fullerene)

Nanoparticles

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Functionally Graded Materials (FGM)

Functionally graded materials

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This is the use of different engineering techniques to produce a composite material with intentional, graded variation of the material properties across its geometry, in order to increase the final product performance. The principal applications are found in thermal barriers, shields, and wear-resistant materials with ductile cores.

Aerogel

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Aerogel is produced by removing water from silica gel. It is replaced with a gas, such as carbon dioxide. The result is a substance that can insulate against high temperatures and absorb unprocessed oil. According to a scientist from the company that is developing this material for NASA, only 18 mm of gel can protect astronauts from temperatures around -130ºC. In the lab, metal sheets covered with 6 mm of aerogel were virtually undamaged by direct dynamite explosions. This material’s applications include low density inertial cores, thermal and acoustic insulation.

http://www.specialchem4polymers.com/tc/adhesion-promoters/index.aspx?id=3307

Coupling agents

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These are chemicals that join immiscible elements or elements that cannot be chemically linked. The coupling agents act as a linking interface between the charges and the composite matrix.

Challenges

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• Productivity

• Specifications

• Processes (RTM, Infusion, SMC, BMC, Filament Winding, etc.)

• Recycling

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