composite fabrication by filament winding

Composite Fabrication By Filament Winding

1. Introduction

Technological advances in various sectors have created the demand

for newer materials, which can perform in stringent conditions of high

pressure and temperature, highly corrosive environment, with high strength

requirement. Conventional materials failed to service these conditions. This

has triggered the need to develop engineered materials to cater customised

needs. Industries have recognised the ability of composite materials to

produce high quality, durable, cost –effective products.

Filament winding is a major manufacturing process in the fabrication of

high performance composites, allowing the process of filament winding to be

the most efficient and least expensive method to construct the basic

infrastructure system of 21st century.

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2. About Composites

A ‘composite ‘is a heterogeneous combination of two or more materials

differing in form or composition on macro scale. The combination results in

material that maximises specific performance properties. The constituents do

not dissolve or merge completely and therefore exhibit an interface between

one another. In this form both reinforcing agents and matrix retain their

physical and chemical identities, while producing a combination of properties

that cannot be achieved with either of the constituents acting alone.

Composites are classified based on type of matrix used –polymer, metallic

and ceramic.

The unique properties of composites are:

1. Composite materials are 30-40% lighter than aluminium structures

designed for the same functional requirements.

2. Pipes and cylinders made up of composites have lower weight

compared to the metallic ones and can be withstand high internal

pressure.

3. Composites have excellent corrosion resistance.

4. Appropriate inhibitors and additives can impart good fire retardation.

properties to composite.

5. Improved torsional stiffness and impact resistance properties.

6. Higher fatigue endurance limit.

7. Design flexibility- composites can be tailored to meet performance

needs and complex design requirement.

8. Composites exhibit higher internal damping capacity.

9. Composites have better dimensional stability.

10. Improved appearance.

Composite applications have revolutionised all industries including,

1. Aerospace 4. Chemicals

2. Pharmaceutical 5. Marine

3. Electrical 6. Transportation

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3. Composite Manufacuring Techniques

There are variety of processing techniques for fabricating composite

parts and structures. They are resin transfer moulding, pultrusion and filament

winding. Some of them are explained bellow in brief:

3.1. Resin Transfer Moulding (RTM):

This is a low pressure, closed mould, semi-mechanised process. In

RTM several layers of dry continues strand mat, woven roving or cloth are

placed in the bottom half of a two part closed mould, and a low viscosity

catalysed liquid resin is injected under pressure into the mould cavity, which is

subsequently cured. Instead of using flat reinforcing layers, such as strand

mat, the starting material in RTM can be a ‘preform‘that already has a shape

of desired product. The potential advantages of RTM can be summarised as:

Manufacture of large complex structures.

Good surface finish.

Design flexibility.

Capability of integrating large number of components into one

part.

APPLICATIONS:

RTM process is mainly used for moulding parts like,

1. Cabinet walls

2. Chairs or bench sheets

3. Hoppers

4. Water tanks

5. Bath tubs

6. Boat hulls

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3.2. Pultrusion:

Pultrusion is a continuous, automated process. Due to uniformity in

cross section, resin dispersion, fibre distribution and alignment, excellent

composite structural materials can fabricate by pultrusion. The process

involves pulling of fibres through a bath of resin, blended with catalyst and

then into a performing fixture, where the section is partially pre- shaped and

excess resin is removed. Then it is passed through a heated die, which

determines the sectional geometry and finish of the final products.

Common pultruded parts are solid rods, hollow tubes, flat sheets and

various types of beams including angles, channels and wide flanged beams.

Advantages of pultrusion process are:

Cost effective for high volume production.

Uniform cross section products can be manufactured.

APPLICATIONS:

1. Industrial grating

2. Walk ways

3. Cable trays

4. Handrails

5. Ladder

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4. Filament Winding Method

4. 1. THE EVOLUTION:

In 1964, authors Rosate D.V. and Grove C.S. in their book ‘filament

winding: It’s Development, Manufacture, Applications and Design’ defined it

as a technique that produces high strength and lightweight products; consist

basically of two ingredients; namely, a filament or tape type reinforcement and

matrix or resin.

The equipment that was designed in1950’s was very basic, performing

the simplest tasks using only two axes of motion (spindle rotation and

horizontal carriage). Machine design consisted of a beam, a few legs and cam

rollers for support. The simplistic design was sufficient to create the first

filament wound parts -rocket motor cases.

By mid-70’s machine design once again made a dramatic shift. This

time the advancement of servo technology entered the real of machine

design. High speed computers allow smoother motion and greater fibre

placement accuracy. Increasingly, function that historically was controlled

through the use of belts, gears, pulleys and chains was eventually being

controlled through the use of computers.

1980’s and 90’s saw the increased use of computer technology.

Machine speed control was greatly improved, and computer control system

could track position and velocity with increased accuracy. At the same time a

number of different companies began to experiment with notion and

development of pattern generation software (CADWIND). By creating pattern

software, more complex configurations such as taper shaft T-shaped parts

and non symmetric parts could be successfully wound.

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4. 2. PROCESS TECHNOLOGY:

To begin with, a large number of fibre rovings are pulled from series of

creels into bath containing liquid resin, catalysts and other ingredients such as

pigments and UV retardants. Fibre tension is controlled by guides or scissor

bars located between each creel and resin bath. Just before entering the resin

bath the rovings are usually gathered into a band by passing them through a

textile thread board or stainless steel comb.

At the end of resin tank, resin –impregnated rovings are pulled through

a wiping device that removes excess resin from the rovings and controls the

resin coating thickness around each roving. The most commonly used wiping

device is a set of squeezed rollers in which the position of the top roller is

adjusted to control the resin content as well as the tension in fibre rovings.

Another technique for wiping the resin impregnated rovings is to pull each

roving separately through an orifice. The latter method results in better control

of resin content. Once the rovings have been thoroughly impregnated and

wiped, they are gathered together in a flat band and positioned on the

mandrel. Band formation can be achieved by passing through a stainless

steel comb and latter through the collection eye. The transverse speed of the

carriage and the winding speed of the mandrel are controlled to create the

desired winding angle patterns.

After winding, the filament wound mandrel is subjected to curing and

post- curing operations during which the mandrel is continuously rotated to

maintain the uniformity of resin content around the circumference. After

curing, the product is removed from the mandrel, either by hydraulic or

mechanical extractor.

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Figure 1: Filament Winding Machine & Processes

Figure 2:

Schematic Representation of the wet filament Winding Process

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4. 3. MATERIALS OF FABRICATION:

Filament winding requires continuous fibre reinforcement and resin

system to bind things together. There are many types of materials that can be

used in this process. The choice of material for a particular product depends

upon the economics, environmental resistance, corrosion resistance, weight

limitations and strength performance requirements.

4.3.1. Reinforcement type:

Continuous fibre reinforcement provides structural performance

required of the final product. A fibre is a primary contributor to the stiffness

and strength of the composite. The dominant commercially available fibres

are

E –Glass

S –Glass

Aramid

Carbon /

graphite

Their common characteristics are,

1. Good tensile strength and stiffness

2. Widely used in commercial and industrial products.

4.3.2. Resins:

The resin matrix provides the load transfer mechanism

between fibres that are wound on to the structure. In addition to

binding the composite structure together, the resin matrix provides

corrosion resistance, protects fibre from external damage and

contributes to the overall toughness from surface impact, cuts,

abrasion and rough handling. A few major resin matrix families of

interest to the filament winders are,

General purpose polyester

Improved polyester

Epoxy

Vinyl ester

Bisphenol

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The common characteristics are,

1. Low cost system

2. Widely used in industry 3.Applicable for room

temperature

4.3.3. Additives:

By using various additives liquid resin systems can be made

suitable to provide specific performance. Specific purpose

additives include,

1. Ultraviolet radiation screens for improved

weatherability.

2. Antimony oxides for flame retardation.

3. Pigments for colouration

4. 4. WINDING METHODS:

There are two different winding methods:

4.4.1 Wet winding, in which the fibres are passed through a resin

bath and wound onto a rotating mandrel to get the final product.

4.4.2 Pre-preg winding, in which pre-impregnated fibre tows are

placed on the rotating mandrel to get the final product. In this

process is in pre-pregged form, so a resin bath is not needed.

Material is heated as it is wound on the mandrel, a process known

as curing ‘on the fly’. the pre- preg is heated, layed down,

compacted and cooled in a single continuous operation.

Among these winding methods, wet winding is more

commonly used for manufacturing fibre reinforced thermosetting

matrix composite cylinders. Compared with pre-preg winding, wet

winding has several advantages like

Low cost

Short winding time

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The resin formulation can be easily varied to meet

specific requirements.

4. 5. WINDING PATTERNS:

In filament winding, one can vary winding tension, winding

angle and resin content in each layer of reinforcement until

desired thickness and strength of the composite are achieved.

The properties of finished composite can be varied with the type

of winding pattern selected.

4.5.1 Hoop winding:

It is known as girth or circumferential winding. Strictly

spiking, hoop winding is high angle helical ending that approaches

an angle of 90degrees. Each full rotation of mandrel advances the

band delivery by one full band width as shown in fig. 3.

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Figure 3

Hoop Winding

4.5.2. Helical Winding:

In helical winding, the mandrel rotates at a constant speed

while the fibre feed carriage transverses back and forth at a speed

regulated to generate the desired helical angles as shown in fig.4.

Usually all composite tubes and pressure vessels re produced by

means of helical winding.

Figure 4

Helical Winding

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4.5.3. Polar winding:

In polar winding, fibres passes tangentially to the polar

opening at one end of the chamber, reverse direction and

passes tangentially to the opposite side of the polar opening at

the other end. In other words, fibres are wrapped from pole to

pole, as mandrel arm rotates about the longitudinal axis as

shown in fig.5. It is used to wind almost axial fibres on domed

end type of pressure vessels. On vessels with parallel sides, a

subsequent circumferential winding is done.

On the above three, helical winding has great versatility.

Almost any combination of diameter and length may be wound

by trading off wind angle and circuits to close the e patterns.

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Figure 5

Polar Winding

5. Recent Advances

Now a day, most filament windings are numerically

controlled with high degree of freedom to place the fibres at

required positions for meeting the complex design configurations

of the products. Fibre orientation is the decisive factor in the

strength of the composites.

Belgium has developed user –friendly pattern generation

software CADWIND for obtaining custom fibre orientation and

high quality of filament wounds components. CADWIND

calculates from the given strength requirements, the fibre lay-up

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on the mandrel and automatically generates the part programme

for any winding machine. The laminate structure is reproduces on

the winding machine exactly as calculated by CADWIND. A

CADWIND design software tool creates 3D mandrel models and

also interfaces for input of mandrel models from cad system.

Optimisation of winding angle variation is possible with this

software. Computer numerical controlled multi-axis filament

winding machines using CADWIND software can wind any

irregular shapes with no axis of symmetry.

6. Indian Scenario

In view of the crucial need for developing indigenous

capability in composite technology, the Advanced Composite

Programme was launched by the Department of Science and

Technology (Government of India). Based on the direct exposure

of Technology Information, Forecasting and Assessment Council

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(TIFAC) to composite applications, the responsibility of

implementing the programme was assigned to this council. The

programme was an attempt to enhance the utilisation and

application of composite as an important performance material in

various sectors and to improve upon the laboratory- industry

linkages towards development and commercialisation.

Assessing the importance of filament winding technology

for novel applications, the following projects have been launched

under the Advanced Composites Programme in collaboration with

industry partners.

6.1. Composite pressure vessels:

The project was launched in March 2002 under the

advanced composite programme of TIFAC in partnership with

Kineco Pvt. Ltd., Panaji and with technological support from IIT

Mumbai. The project aimed at developing filament wound

pressure vessels.

The project aimed at developing filament wound pressure

vessels for the following applications,

1. Under carriage tanks to be fitted to the railway passenger

coaches for water supply to the toilets.

2. For water treatment application.

6.2. Filament wound GRE pipes:

In view of the wide application potential of GRE pipes, a

project on development of glass reinforced epoxy (GRE) pipes by

filament winding technique is being considered by TIFAC. GRE

pipes will be developed as per ASTM standards, using

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indigenously developed 4 axes CNC filament winding system for

catering to high pressure applications.

GRE pipes offer resistance to highly corrosive fluids at

various pressure and temperatures, and adverse soil and weather

conditions.

The project aimed at developing filament wound GRE pipes

for the following applications,

1. In oil refineries.

2. Offshore flat forms.

3. Chemical and pharmaceutical plant.

4. Sewerage, heating, cooling of fluid lines.

6.3. Filament wound composite pipe fittings:

At present FRP pipe fittings in India are being

manufactured by hand lay –up or by tape winding which cannot

withstand high pressures and temperatures. Due to non uniformity

in fabrication and resultant mechanical properties, the service life

of such pipe fittings is also minimal.

In view of application potential of filament wound pipe

fittings, a project on ‘development of filament wound composite

pipe fittings’ is being considered by TIFAC. Under the project,

there is proposal to fabricate composite pipe fittings using

indigenously developed six axis CNC filament winding system.

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Figure 6 .Six-Axis Computer-Controlled Filament Winder

The project aimed at developing filament wound composite

pipe fittings for the following applications,

1. Oil exploration and transportation.

2. Refineries.

3. Chemical and pharmaceutical plants.

4. Irrigation.

5. Nuclear and thermal power plant.

6. Fire fittings.

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7. Advantages & Limitations

Advantageous points of filament winding method as

compared to other manufacturing techniques of composites

are:

This technique offer high speed.

This is precise method for placing many composite

layers.

This is low cost method.

This is the fastest technique for manufacturing fibre

reinforced cylindrical components and high pressure

pipes.

This process is not limited to axis- symmetric structures.

This method is efficient for more complex parts such as

Tee joints, Elbows.

Attractive external appearance of the product.

Cost comparison between composites fabrication methods.

Limitations:

This method is limited for cylindrical, spherical & dome

shaped structures.

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Setup cost is high.

8. Applications of Filament Winding Method

1) Aerospace-applications include,

Tailcone assemblies

Drive shafts

Masts

Turrets

Rocket Motor Cases

Launch Tubes

Fuel Tanks

2) Corrosion Resistant

Ducting Systems

Underground Storage Tanks

Above Ground Storage Tanks

Piping Systems

Stack Liners

3) Sport’s and recreation

Golf Shafts

Bicycle Tubular Structures

Wind Surfing Masts

Ski Poles

4) Pressure Vessels

Water Heaters

Rocket Motor Casings

CNG (Compresses Natural Gas) Tanks

Solar Heaters

5) Roller Shafts

Paper rollers

Liners

Ducting Systems

Tubular Systems

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AEROSPACE AND CUSTOM DESIGN APPLICATIONS

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Image no. 8 Image no. 9

ROLLER SHAFT DRIVE SHAFT

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Image no.10 Pressure vessel

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9. Conclusion

By using filament wound processes application never

corrode and remain maintained free for decades, competing in

cost and performance with the metallic structures.

Filament wound composite pipe are good replacement for

all steel and metal pipelines in oil, gas and water supply systems.

There is substantial need to renovate and restore all municipal

pipe lines for water and sewerage transportation with composites.

India with an excellent knowledge base in various resins,

catalyst and curing systems with an adequate availability of raw

materials can certainly shape out a role in the emerging

technology of composite fabrication. Commercialising this

technology will bring about a steady growth in Indian economy.

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10. References

Following are the sources from where the information for

the seminar has been collected:

1) Engineering Materials

(By Budinski)

2) Material Science & Metallurgy

(By Yesudian & Samual)

3) Publisher; Search: The industrial sourcebook.

Edition: January 2004

Page no. From 222 to 232.

WEBSITES:

1. www.compositesworld.com

2.

www.compositetek.com/papers/preformSAMPEPAPER.pdf

3. INCORPORATING ENVIRONMENTAL ISSUES IN A FILAMENT WINDING COMPOSITE MANUFACTURING SYSTEM BY Dawn K. Russell, Phillip A. Farrington, Sherri L. Messier James 4. Metal Prepare Filament Winding Brian Gordon Touchstone Research Laboratory, Ltd., Triadelphia, WV 5. OPTIMAL DESIGN OF FILAMENT WOUND STRUCTURES UNDER INTERNAL PRESSURE BASED ON THE SEMI-GEODESIC PATH ALGORITHM BY Cheol-Ung Kim, Ji-Ho Kang, Chang-Sun Hong and Chun-Gon 6. Economic assessment of Product-Process Innovation in Filament Winding Technology by Daniele Romano and Paola Pedone

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http://www.compositetek.com/papers/preformSAMPEPAPER.pdf


7. COMPOSITE MANUFACTURING 8. Composite Fabrication by Filament Winding - An Insight Muttana Suresh Babu, Gudavalli Srikanth & Soumitra Biswas

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