COMPOSITE TECHNOLOGY LABORATORYRene Herrmann 2011

Composite material

Materials constist of at least 2 components, MATRIX and REINFORCEMENT.

MATRIX is resin REINFORCEMENT is fiber Resin types are polyester, vinylester,

epoxy Fiber types are glas, carbon and aramid

fibers (aramid is kevlar)

Characteristics

Composites are unisotropic materials (theri characteristics depend on the direction (fibers)

Composites are chemically (rather) stable, strong and stiff as compared to their mass

Composites are more expensive than traditional materials (metal) and their strength collapses at around 200C.

Composites challanges

Manufacturing of composite products is complex and often slow.

Interconnections between composites are difficult, optioins are seconary bonding and clueing

Composites degrade in UV light and need surface coatings that protect the resin MATRIX

Composite manufacturing requires a mould, form or plug to laminate on

Composite moulds

The product must be laminated, a mould is needed Moulds must release the laminate after it has been

made (release agent on many such are needed) Moulds must have a better surface finish than the

product you are making. Moulds are often milled and then polished. Hand polishing is done until until 400 sandpapper

and 800 to 1200 (2000) with water sandpapper and after that with polishing machine to ’optical’ surface finishes

Hand polishing takes 20 to 30 hours/m^2, this is what makes mould costs high.

Composite manufacturing

Composites are LAMINATES, sometimes with a surface finish or without, in later case they are often painted later.

Composites are made because of the strength to mass ratio or because they are chemically corrosion resistant

Strength is defined by where is the young modulus and is the strain in the composite.

Basic composite strength

Strength is . Force is and is cross section to force. The composite breaks if the strain of EITHER RESIN

or FIBER is reached. The youngs modulus resisting the strain in the

material is actucally a function of youngs modulus of both resin and fiber and their VOLUME FRACTION

Composite youngs modulus is . The volume fraction is .

The above equation is approcximative because it does not contain the volume fraction of VOIDS (holes) in the laminate.

Lamination process

Composite lamination process has mainly 2 technical desires.

The fibers are clean and neatly placed in the direction where the forces act

The resin matrix is applied to the fibers such the ALL FIBERS are WETTED with the minimum amount of resin and with ZERO VOID CONTENT.

The fiber volume fraction is to be as high as possible and any means technically applicable are to be used to get the VOLUME FRACTION preferably .

Composite market in Finland

The market is small and export oriented. There are 3 big market section in Finland( Boats,

Aircraft, chemical industry) NCE Oy (chemically corrosion resistant materials

for heavy industry) Nautor Swan and Baltic yachts, marine super yacht

construction, low mass and sea water tolerant Kesko marine, marine mass producer, motor speed

boats, sea water resistant and some low mass issues

Air craft part manufacturing (Airbus A 380 spoilers, Patria Oy, low mass)

Future composite market in Finland

The marine lamination capacity in Finland is large and high tech and suffers of economic down turn.

Vihicle sector (trucks and train parts) is starting to establish itself (small scale)

Chemical sector is expanding Sports equipment on small scale is coming

(wake bord, kite bord, skis) Wind turbine market is coming but very

competitive Aircraft market is small and remains marginal

Self study (3h, no report but all questioin do come in exam )

What is glue and what is resin? What is the difference between polyester,

vinylester and expoxy (table with (strength, strain, chemical and thermal stability, price, viscosity)?

How is resin setting (geltime, barcol hardness, post cureing)?

What is hand lamination, vacuum infusion, vacuum bagging and auto clave lamination?

Which fiber volume fractions can be reached with above methods?