Intro to Composites and Adhesive Bonding

7/17/2019 Intro to Composites and Adhesive Bonding

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Composite Materials

Materials that are made ofmore than one materials, in a

macroscopic scale is called as acomposite. This should not beconfused with alloys which is a

microscopic scale mixture.Could be inhomogeneous andanisotropic.



Types of Composites

Particle Reinforced

Fiber Reinfoced Structural

Large

Particles

Dispersion

Strengthened

Continous

(aligned)

Discontinous

(Short)

AlignedRandomly

Oriented

Laminated Sanditch

Concrete Precipitation

Hardened

Alloys

Pre- pregs

Reinforcements ! "atri# $ Composites

Veneer Helicopter

Blades

Pultruded

Rods

Sports

Components



Constitution of

Reinforced CompositesFIBR Carbon, !raphite, Metal "#l, Boron, ..$,

%e&lar, Ceramics'.

M#TRI( )olymer, Carbon, Metal, Ceramics, Cement,

#sphalt..

)#RTIC*+#T

!ra&el, Rubber, )recipitates'..+#-R +aminated, Bonded, oneycomb

andwich'.



/#T# T



Polymer Resin TypesPolymers fall within one of two basic groups: thermosetting plastics andthermoplastics. A thermosetting, or thermoset, resin "cures" into an irreversible state

because its molecular structure is cross-linked. A thermoset resin iscomparable to an egg. Once its cooked, it essentially stays in the

same state. !amples of thermoset resins for composites areunsaturated polyester, vinyl ester, epoy, urethane and phenolic.

On the other hand, a thermoplastic resin has a linear molecularstructure that will repeatedly soften when heated to its melttemperature and harden when cooled. #n simple terms, athermoplastic is comparable to paraffin wa, which flows when

heated and hardens to a set shape when cooled. !amples ofthermoplastic resins for composites are polypropylene,polyethylene, polystyrene, A$% &acrylonitrile-butadiene-styrene',nylon, polycarbonate, thermoplastic polyester, polyphenylene oide,polysulfone and P!!( &poly-ether-ether-ketone'.



In0ection Molding

A thermoplastic or thermoset molding compound

made of glass fibers and resin is fed by a screw

or plunger into a mold cavity. )he mold halves are

held under pressure until the resin cures.



In0ection Molding

*or in+ection and compression molding, glass and resin are usually combined in a ready-to-mold reinforcementresin compound.

lass fiber-reinforced thermoplastic compounds are typically in the form of pellets consistingof hopped %trands, the resin and application-specific fillers and additives.

*or reinforced thermoset resins, there is bulk molding compounds &$/' and sheet moldingcompound &%/'. $/ is a miture of hopped %trands, resin and application-specific catalyst,

fillers and additives. )he pre-mied material has the consistency of molding clay and is in+ectedinto a mold cavity or placed on the bottom of two mold halves for compression molding.

%/ is produced in a highly-automated continuous flow process. ontinuous roving ischopped to a desired length and deposited onto a resin-filler paste that is conveyed on a web ofplastic film. A top layer of paste and film is added, and the resinreinforcement mi between thefilm is compacted and rolled into a sheet. )he resin "matures" to a state that gives the sheet theconsistency of leather. )he film is peeled away, and the sheet is cut and stacked into apredetermined pattern or "charge" that is placed on the bottom of the mold. )he top mold half islowered, and the %/ is compression-molded into the final part.

A prepreg is an intermediate composite form made by preimpregnating the reinforcement withresin prior to molding.

A preform is an intermediate reinforcement form that ensures uniform properties by maintainingglass fiber placement as resin flows inside the mold cavity. Approimating the shape of thefinished part, a prepreg typically consists of chopped fibers held together by a resinous binderor continuous filament mat impregnated with a thermoformable binder.



Resin Transfer Molding

)he reinforcement isplaced in the bottomhalf of matching

molds. After the moldis closed andclamped, resin ispumped underpressure into the mold

cavity. )he resin wetsthe reinforcement andcures to form thecomposite part.



Reinforced Reaction In0ectionMolding

)his is similar to structuralreaction molding.

*or 00#/, thereinforcement is added to

both resin componentsbefore those componentsare reacted.

)he fiber-reinforced resincombination is in+ected

into the mold cavity wherethe resin rapidly reactsand cures to form thecomposite part.



)ultrusion

•Continous processing for making a lineal profile with a constant cross

section &such as rod stock, poles, beams, channels and tubing'.•After the reinforcement is impregnated with resin, the material is

pulled through a heated die that gives the part its cross sectional

shape. )he resin cures to create the composite profile.

•Fe parameters for process control%



Filament 1inding)his process makes high strength, hollow and generally

cylindrical products such as pipe, storage tanks, pressure

vessels and rocket motor cases.

)he fiber is impregnated in a resin bath and pulled by the

force of a rotating mandrel which gives the part its shape.

1eils are used for inner andor outer surfaces to create a

resin-rich surface for better corrosion resistance and

aesthetics.



Continous +amination

This is a process for making composite in sheet form such as

composite glazing, corrugated or flat construction panels, and

electrical insulating materials. Reinforcement is combined with

resin and sandwiched between two plastic carrier films. The

sheet takes shape under forming rollers, and the resin is curedto form the composite



and +ay2up

)his process is suited for making large, highstrength parts at low to medium volumes. Acombination of reinforcements in roll form is laidinto an open mold and impregnated with resin. 2hen

the resin cures, the surface of the mold is replicatedon the side of the composite facing the mold.



3/T of Composites

Critical Flaw i4e /e5nition is /i6cult.

#nomaly /etection and not Flaw/etection

Flaws include )orosity, Fiber Brea7age,/elamination, 1arping, Moisture#bsorption, etc.

)rimary Methods are *ltrasonics and

Thermography.econdary Methods are Radiography,#, #coustic Impact, and hearography



Typical Results



#dhesi&ely Bonded

tructures3eed to replace mechanical 0oints8fastners such as ri&ets,welds, screws, nails''

#d&antages 9 #dhesi&es distribute load moree&enly, ma7ing a 0oint more resistant to stress.#dhesi&es seal as well as bond, which eliminates

the corrosion that can occur in a mechanicallyfastened 0oint. #dhesi&es more easily 0oinirregularly shaped surfaces. #nd adhesi&es addno appreciable change in part weight orgeometry. no stress concentration risers, no protrudingob0ects, better esthetics,..$

/rawbac7s 9 the time it ta7es for strength to beachie&ed, the need for surface preparation andthe potential need for future disassembly.

3/T is %-



Manufacturing )rocesselection of #dhesi&e Resin Type

#dhesi&e )reparation

urface )reparation

#dhesi&e #pplication and :ig )rocessCuring )rocess "with heat, *;, moisture$

Finishing



Types of :oints



<ect of Temperature



<ect of urface

Treatment



Types of /efects in

Bonds/isbonds due to o&er stresscondition such as impact or bending.

1ea7 Cohesi&e properties caused bydegradation of resin or due to poorprocess control or due to impropercuring.

Interfacial 1ea7ness or %issingBonds due to poor surfacepreparation or interfacialcontamination during processing.



3/T Methods

/isbonds 9 *ltrasonics,hearography, #coustic Impact,olography, Thermography'..

Cohesi&e 1ea7ness9 ResonanceMethods

%issing Bonds9 =bli>ue hear 1a&e

Methods, 3on2linear *ltrasonics,/oppler based *ltrasonics,hearography, '.



Damage Detection

Null zone based scanningmethods shown to be moresensitive to damage in bondedand composite structures.

Long range and inaccessiblearea damage detection for lap

joints and riveted areas

Intro to Composites and Adhesive Bonding

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