Manufacturing Processes of Composite Structures

Ing. Bohuslav Cabrnoch, Ph.D.

VZLÚ, a.s.

Manufacturing Processes

Manufacturing processes

Wet lay-up

Prepregs

Resin Film Infusion (RFI)

Resin Transfer Molding (RTM)

Vacuum Infusion Process (VIP)

Filament Winding

Braiding

Sheet Moulding Compound (SMC)

Pultrusion

Wet Lay-up

Wet Lay-up

Dry reinforcement impregnated by catalyzed resin Impregnation by roller, brush or spatula Open mould method With or without vacuum compaction Curing at RT Optional post-curing in oven at elevated temperature (usually up to 80°C) Mats, fabrics, gel coat

Wet Lay-up

Gel coat

Surface layer at thickness about 0,5 mm

Pigmented resin (usually UP or EP)

Application by brush, spray

reasons for application

To provide a high-quality finish on the visible surface

To increase lifetime (wearing resistance)

Protective coat against environment (moisture, UV, chemicals)

Prepreg

Prepreg process

Prepreg (pre-impregnated) Reinforcement is already impregnated by matrix resin Requires cold storage (-18°C) to prevent complete curing Limited lifetime Precise fiber volume fraction

Semipreg Reinforcement is already impregnated by film matrix resin

from one side only

Impregnation machine Solvent (solution of resin and solvent)

Hot-melt

Prepreg General manufacturing process Mould preparation

Cleaning, application of release agent

Prepreg cutting Cutting of prepreg layers

Lay-up Temperature, humidity, dustiness

Vacuum bagging Peel ply, release film, breather mat Vacuum bag

Expendable Reusable

Curing Temperature, time, pressure, vacuum

Removing of cured part from mould

Prepreg

Prepreg cutting

Requirements – Precision

– No prepreg contamination

– Marking

Techniques – Tangential knife

– Oscillating knife

– Water jet

Prepreg

Hand lay-up

Requirements – Precision (position, orientation)

– No prepreg contamination

– Elimination of entrapped air

Equipment – Clean Room

– Positioning means

• Gauges / Templates

• Laser projector

Prepreg

Automated lay-up Higher effectivity than hand lay-up

Hand lay-up 0,5 – 1 kg/h

Automated about 10 kg/h

ATL (Automated Tape Laying)

Laying of UD and fabric prepregs and film materials in 3 – 305 mm bandwidths

Big flat parts

Laying, trimming and debulking at once

AFP (Automated Fiber Placement)

Laying of single strands (tow-preg) or Slit tapes (3,2 ÷ 12,7 mm widths)

Small or complex surfaces

Prepreg Vacuum bag materials

Prepreg

Curing

Curing cycle – Temperature – Pressure – Vacuum – Time

Prepreg

Autoclave curing

Přetlak p1

Podtlak p2

1

4

6

5

3

2

Autoclave

Vacuum bag

Trolley

Breather mat

Curing part

Mould

Vacuum

Pressure

Prepreg

Autoclave curing

Heating /

cooling

Autoclave

Air

circulation

Mould

Resin Film Infusion

Resin Film Infusion (RFI)

Impregnation of dry reinforcement by resin film

SPRINT® (SP Systems / Gurit)

LF Technology (5M)

ZPREG® (ACG / Umeco / Cytec)

Resin Film Infusion

Resin Film Infusion (RFI) Comparison with prepregs

Possibility to set fiber volume fraction Simpler logistic – only one type of resin Lower storage requirements - only resin stored in freezer

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Vacuum Infusion Process (VIP)

Impregnation of dry reinforcement in single open mould under a bag Resin injected by vacuum only 50 ÷ 1000 parts / mould / year

Gelcoat Resin supply

Vacuum Vacuum bag

Distribution layer

Part lay-up

Mould

Bleeders

Vacuum distribution/

resin capture

Sealant tape

Infusion Processes

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Resin Transfer Moulding Light (RTM Light )

Impregnation of dry reinforcement in close mould

Back side mould is transparent laminate usually

Resin injected by vacuum only or under low pressure

50 ÷ 1 500 parts / mould / year

Gelcoat

Resin supply

Vacuum

Back side mould Supporting frame

Part lay-up

Mould

Sealant

Infusion Processes

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Resin Transfer Moulding (RTM) Impregnation of dry reinforcement in stiff close mould

Resin injected under pressure 0,2 – 1,0 MPa

Stiff and heavy moulds

500 ÷ 5 000 parts / mould / year

Gelcoat

Resin supply Vacuum Plug Heating

Part lay-up

Cavity

Infusion Processes

Vacuum Infusion Processes Alternative of VIP

CIRTM co-injection RTM Crystic VI vacuum infusion (Scott Bader) DRDF double RIFT diaphragm forming (University of Warwick) LRI liquid resin infusion MVI modified vacuum infusion (Airbus) Quickstep use of liquids for enhanced heat transfer in infusion RIFT resin infusion under flexible tooling (ACMC Plymouth) RIRM resin injection recirculation moulding SCRIMP Seeman Composites Resin Infusion Molding Process VAIM vacuum-assisted injection moulding VAP vacuum assisted processing (patented by EADS) VARI vacuum assisted resin injection system (Lotus Cars) VARIM vacuum assisted resin injection moulding V(A)RTM vacuum (-assisted) resin transfer moulding VIM vacuum infusion moulding. VIMP vacuum infusion moulding process VM/RTM Light a hybrid RIFT/RTM (Plastech)

Filament Winding

Filament Winding

Laying of impregnated yarn on rotating mandrel / liner

Circular and non-circular cross-sections

Shafts, pressure vessels

Filament Winding

Filament Winding

Helical pattern winding

Polar method

Braiding Braiding

Dry preform manufacturing

Impregnated by infusion processes

Circular and non-circular cross-sections

SMC (Sheet Moulding Compound) Prepreg sheets cured into matched metal dies under heat and pressure

Prepregs SMC - R – chopped fibers - CR – continuous + chopped fibers - XMC – continuous reinforcement

UP or VE resin

Sheet Moulding Compound

Pultrusion

Pultrusion

Pultrusion is an automated process used to create

shapes by pulling rovings through a shaped and

heated die

Manufacturing Processes

Comparison of manufacturing processes according to achievable fiber volume fraction

Process Fibre Volume Fraction [%]

Wet Lay-up 10 – 38

Prepreg 50 – 70

RFI 45 - 60

RTM 25 – 65

VIP 25 –50

Braiding 25 – 65

Filament Winding 45 - 65

Pultrusion 43 - 83

Thermoplastics

Manufacturing of thermoplastic composites

Press forming

Matched metal dies

Elastomeric tool

Autoclave

Vacuum forming

Thermoplastics

Press forming

Thermoplastics

Press forming – typical parts

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Moulds

Requirements Temperature resistance

Dimensional stability

Lifetime

Thermal expansion

Materials Metallic

– Al alloys – Steel – Invar – Electroforming

Non-metallic

– Wood MDF (Medium Density Fibreboard)

Matchboard

Tooling

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Moulds

Materials Non-metallic

– Block materials EPS, XPS

PUR

EP

– Composite Glass, Carbon fibers

UP, EP

Wet lay-up, prepreg, spray-up

Gelcoat

Tooling

Tooling

Moulds

Single open moulds

Pressure bag moulding

Autonomy heated moulds

Tooling

p

1

2

3

Curing oven

Curing part

Pressure bag moulding

Pressure bag moulding

Curing pressure is induced by flexible bag

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Master models (Plugs)

Requirements Temperature resistance

Dimensional stability

Thermal expansion

Materials Block materials

– EPS, XPS – PUR – Axson, Ebalta, OBO, Rampf, Necuron

Model pastes

MDF (Medium Density Fibreboard)

Matchboard

Tooling

Machining

Machining

Conventional Water Jet

Machining

Conventional machining

Tooling materials – HSS (coatings) – Carbide (coatings) – Polycrystalline Diamond (PCD)

• Inserts

Manual – Pneumatic and electric tools

• Guides / Templates • Trimming fixtures

– Dustiness – dust exhaust • Carbon - explosive

atmosphere

Machine – CNC mills – Robot platforms

Machining

Conventional machining - contour

Straight edges Diamond saw blades

Complex shape edges End mills

Reciprocal saw

Machining

Conventional machining - holes

Tooling materials

Carbide

Polycrystalline Diamond (PCD) - inserts

Drilling

Milling

Countersinking

Machining

Conventional machining - holes

Standard drill bits – delamination

Special geometry of tool face

8 Facet drill

Kevlar drill

Reamer drill

Dagger drill

Precise holes

Reamers

Machining Honeycomb machining

Expanded

High speed spindles

Ultrasound

Non-expanded blocks

Band / circular saw

Milling

Machining Honeycomb machining– high speed spindle

Complex shapes

Chamfering / Cut-outs Limitation by tool shape

Sandwich panels

Machining

Honeycomb machining– high speed spindle

Tools

Roughing cut

Finishing cut

Materials

HSS

Carbides

Coated Carbides

Diamond

Machining

Honeycomb machining – ultrasound

Oscillating knife

Frequency 20 kHz

Cut-offs, chamfering

Sharp edges

Machining

Water jet

CNC machines

Robot platforms

A mixture of water and an abrasive substance

No heat-affected zone

Dust free, no fumes

Low cutting forces