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Home Publications Composite Fabrication by Filament Winding - An Insight

Composite Fabrication by Filament Winding - An Insight
Muttana Suresh Babu, Gudavalli Srikanth & Soumitra Biswas

1.0 Introduction

The technological advances in various sectors have created demand for newer materials, where they are required to perform in stringent conditions - high pressure & temperature, highly corrosive environments, with high strength requirement, which the conventional materials failed to service.

This has triggered the development needs for engineered materials to cater to customized needs. Industry has recognized the ability of composite materials to produce high-quality, durable, cost-effective products.

While the concept of composites has been in existence for several millennia, the incorporation of composite technology into the industrial world is less than a century old. The first known polymer composite product was a boat hull manufactured in the mid 1930’s as part of a manufacturing experiment using a fibreglass fabric and polyester resin laid in a foam mould.

From such a beginning, composite applications have revolutionized entire industries, including aerospace, marine, and electrical, chemical/ pharmaceutical, transportation etc.

Composites have proved to be a worthy alternative to other traditional materials even in the high-pressure situations of chemical processing. Besides superior corrosion resistance, composite materials exhibit good resistance to temperature extremes and wear, especially in industrial settings.

The tailorability of composites for specific applications has been one of its greater advantages and also one of its most perplexing challenges to adopt them as an alternative material for metallic ones. The composites industry has now begun to recognize that the composites promise to offer excellent business opportunities in an array of applications.

2.0 Why Composites?

A 'composite' is a heterogeneous combination of two or more materials (reinforcing agents & matrix), differing in form or composition on a macroscale.

The combination results in a material that maximizes specific performance properties. The constituents do not dissolve or merge completely and therefore normally exhibit an interface between one another. In this form, both reinforcing agents and matrix retain their physical and chemical identities, yet they produce a combination of properties that cannot be achieved with either of the constituents acting alone.

Composites are commonly classified based on the type of matrix used: polymer, metallic and ceramic. In fibre - reinforced composites, fibres are the principal load carrying members, while the surrounding matrix keeps them in the desired location and orientation.

Matrix also acts as a load transfer medium between the fibres, and protects them from environmental damages due to elevated temperatures, humidity and corrosion. The principal fibres in commercial use are various types of glass, carbon and Kevlar. All these fibres can be incorporated into a matrix either in continuous or discontinuous form. Composites have unique properties as follows:

  • Composite materials are 30-45% lighter than aluminium structures designed for the same functional requirements
  • Pipes/cylinders made of composites, with lower weight compared to the metallic ones, can withstand high internal pressures
  • Excellent corrosion resistance
  • Appropriate inhibitors/additives can impart very good fire retardance properties in composites
  • Improved torsional stiffness and impact resistance properties
  • Higher fatigue endurance limit (upto 60% of the ultimate tensile strength)
  • Design flexibility (composites are more versatile than metals and can be tailored to meet performance needs and complex design requirements)
  • Composites exhibit higher internal damping capacity
  • Composites have better dimensional stability over temperature fluctuations due to low coefficient of thermal expansion
  • Composites enjoy lower life cycle cost compared to metals
  • Composite parts can eliminate joints/fasteners, providing part simplification and integrated design compared to conventional metallic parts
  • Improved appearance with smooth surfaces
3.0 Manufacturing Techniques

The end properties of a composite part are not only contingent upon the properties of fibre & resin matrix, but also depend on the way by which they are processed. There are variety of processing techniques for fabricating composite parts/structures viz. resin transfer moulding, autoclave moulding, pultrusion and filament winding.

Out of these processes, filament winding is a low cost and the fastest technique for manufacturing of fibre reinforced cylindrical components and high-pressure pipes. Brief description of various fabricating processes is as follows :

3.1 Resin Transfer Moulding

This is a low-pressure, closed mould semi-mechanized process. The process enables fabrication of simple low to high performance articles in varied sizes and profiles. The RTM process has been successfully used in moulding of complex three - dimensional shapes in one piece.

RTM is mainly used for moulding parts such as cabinet walls, chairs or bench sheets, hoppers, water tanks, bathtubs, boat hulls etc. In RTM, several layers of dry continuous strand mat, woven roving or cloth are placed in the bottom half of a two-part closed mould and a low-viscosity catalyzed liquid resin is injected under pressure into the mould cavity, which is subsequently cured.

Instead of using flat reinforcing layers such as a continuous strand mat, the starting material in RTM process can be a ‘preform' that already has the shape of the desired product. The potential advantages of RTM can be summarized as rapid manufacture of large, complex, high performance structures with good surface finish on both sides, design flexibility and capability of integrating large number of components into one part.

3.2 Pultrusion

Pultrusion is a continuous, automated process that is cost effective for high volume production of parts with uniform cross-section. Due to uniformity in cross-section, resin dispersion, fibres distribution & alignment, excellent composite structural materials can be fabricated by pultrusion.

The process involves pulling of fibres through a bath of resin, blended with a catalyst and then into a performing fixture, where the section is partially pre-shaped & excess resin is removed. It is then passed through a heated die, which determines the sectional geometry and finish of the final product. Composite sections with highest fibre content can be achieved by pultrusion.

The common pultruded parts are solid rods, hollow tubes, flat sheets and various types of beams including angles, channels, hat-sectioned and wide-flanged beams.

The profiles produced by this process can compete with traditional metallic profiles made of steel & aluminium for strength & weight. Pultruded sections find excellent applications for fabricating industrial gratings, walk-ways, cable-trays, hand-rails, ladders and also for structurals in corrosion prone areas, chemical plants, off-shore and on-shore operations etc.

3.3 Filament Winding

In a filament winding process, a band of continuous resin impregnated rovings or monofilaments is wrapped around a rotating mandrel and then cured either at room temperature or in an oven to produce the final product. The technique offers high speed and precise method for placing many composite layers.

The mandrel can be cylindrical, round or any shape that does not have re-entrant curvature. Among the applications of filament winding are cylindrical and spherical pressure vessels, pipe lines, oxygen & other gas cylinders, rocket motor casings, helicopter blades, large underground storage tanks (for gasoline, oil, salts, acids, alkalies, water etc.).

The process is not limited to axis-symmetric structures: prismatic shapes and more complex parts such as tee-joints, elbows may be wound on machines equipped with the appropriate number of degrees of freedom.

Modern winding machines are numerically controlled with higher degrees of freedom for laying exact number of layers of reinforcement. Mechanical strength of the filament wound parts not only depends on composition of component material but also on process parameters like winding angle, fibre tension, resin chemistry and curing cycle.

3.3.1 Filament Winding Technology – The Evolution

In 1964, the authors, Rosato D.V and Grove C.S. in their book titled, Filament winding: Its Development, Manufacture, Applications and Design defined it as a technique which "…produces high-strength and lightweight products; consists basically of two ingredients; namely, a filament or tape type reinforcement and a matrix or resin".

The unique characteristics of these materials made great revolutions for many years .The concept of filament winding process had been introduced in early 40's and the first attempt was made to develop filament-winding equipment.

The equipment that was designed in 1950'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. Initial advancements came in the form of mechanical systems that allowed an operator to program a machine by the use of gears, belts, pulleys and chains. These machines had limited capabilities and capacities, but were accurate.

Eventually through technical innovations, engineers were able to design servo-controlled photo-optic machines with hydraulic systems. The desired fibre path was converted into machine path motion through a black-white interface on a drum; which was followed by a photo-optic device that controlled the machine function.

During this time the filament winding machine became increasingly sophisticated in design; the addition of a third axis of motion (radial or crossfeed carriage), profile rails and ball shafts in combination with improved gearboxes resulted in smoother, more accurate filament winding.

By mid-70’s, machine design once again made a dramatic shift. This time the advancement of servo technology entered the realm of the machine design.

High-speed computers allowed for rapid data processing, resulting in smoother motion and greater fibre placement accuracy. Increasingly, function that historically was controlled through the use of belts, gears, pulley and chains was eventually being controlled through the use of computers.

The 1980s and 90s saw the increased use of computer technology. Computers and motion control cards became essential pieces of hardware that were included in almost every machine.

Machine speed control was greatly improved; computer control systems could track position and velocity with increased accuracy. Additional axes of motions were also incorporated into machine design; allowing for four, five and even six axes of controlled motion!

At the same time a number of different companies began to experiment with the notion and development of pattern generation software (FiberGrafiXTM and CADWINDTM). By creating pattern generation software, more complex configurations, such as tapered shafts, T-shaped parts and non-axisymmetric parts could be successfully wound.

3.3.2 Industrial Importance of Filament Winding Process

Since this fabrication technique allows production of strong, lightweight parts, it has proved particularly useful for components of aerospace, hydrospace and military applications and structures of commercial and industrial usefulness.

Both the reinforcement and the matrix can be tailor- made to satisfy almost any property demand. This aids in widening the applicability of filament winding to the production of almost any commercial items wherein the strength to weight ratio is important. Apart from the strength-to-weight advantages and low cost of manufacturing, filament wound composite parts have better corrosion and electrical resistance properties.

3.3.3 Filament Winding: Process Technology

To begin with, a large number of fibre rovings is pulled from series of creels into bath containing liquid resin, catalyst and other ingredients such as pigments and UV retardants. Fibre tension is controlled by the 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.

Fig 3.1 Schematic representation of the wet filament winding process

At the end of the resin tank, the resin-impregnated rovings are pulled through a wiping device that removes the excess resin from the rovings and controls the resin coating thickness around each roving.

The most commonly used wiping device is a set of squeeze 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 later through the collecting 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 uniformity of resin content around the circumference. After curing, product is removed from the mandrel, either by hydraulic or mechanical extractor.

3.3.4 Materials of Fabrication

Filament winding requires continuous fibre reinforcement and a resin system to bind things together. There are many types of materials that can be used in this process. The choice of materials for a particular product depends more upon the economics, the environmental resistance, corrosion resistance, the weight limitations and the strength performance requirements all play an important part in this decision :

(i) Reinforcement Type : Continuous fibre reinforcement provides the structural performance required of the final part. The fibre is the primary contributor to the stiffness and strength of the composite. The dominant commercially available fibres are: E-glass, S-glass, aramid and carbon/graphite systems. To summarize these systems :

  • E-Glass ¾ good tensile strength (3450 MPa), low tensile modulus (70 GPa), lowest cost fibre, available in many forms, widely used in commercial and industrial products, most-used in filament winding;
  • S-Glass ¾ improved strength (4600 MPa), higher tensile modulus (85 GPa), higher cost fibre, used in aerospace and high performance pressure vessel applications;
  • Aramid ¾ good strength (2750 MPa), higher tensile modulus (130 GPa), higher cost fibre, very low density (one-half of glass fibre), excellent impact and damage tolerance properties, poor compression and shear strength.
  • Carbon/Graphite ¾ wide strength range (2050 to 5500 MPa) highest modulus (210-830 GPa), highest fibre cost, intermediate density (two-thirds of glass fibre), poor impact or damage tolerance, best tensile strength and stiffness properties.
(ii) Resins :

The resin matrix that holds everything together, provides the load transfer mechanism between the fibres that are wound onto the structure.

In addition to binding the composite structure together, the resin matrix serves to provide the corrosion resistance, protects the fibres from external damage, and contribute to the overall composite toughness from surface impacts, cuts, abrasion, and rough handling.

Resin systems come in a variety of chemical families, each designed to provide certain structural performance, cost, environmental, and/or environmental resistance. (Note: Only the thermoset family is covered in this article.) A few major resin matrix families of interest to filament winders are:

  • General Purpose Polyester ¾ classified as orthophthalic polyesters, lowest cost systems, widely used in FRP industry, moderate strength and corrosion resistance, room temperature curing.
  • Improved Polyester ¾ classified as isophthalic polyesters, slightly higher cost, good strength and corrosion resistance, widely used in FRP corrosion applications, room temperature curing
  • Epoxy ¾ wide range of resins available, best strength properties, curing at elevated temperature, good chemical resistance, higher viscosity systems, higher material cost, applications across broad market segment range.
  • Vinyl Ester ¾ chemical combination of epoxy and polyester technology, excellent corrosion resistance, higher cost, excellent strength and toughness properties, widely used as corrosion liner in FRP products.
  • Bisphenol-A Fumarate, Chlorendic ¾ more exotic systems for improved corrosion resistance in harsh environments, higher cost resins, higher temperature capability, applications in paper & pulp industry; and
  • Phenolic ¾ possess excellent flammability properties (e.g. flame retardance, low smoke emissivity), higher cost systems, lower elongation, moderate strength, applications involve fire resistant systems structures
iii) Additives:

By using various additives liquid resin systems can be made suitable to provide specific performance. Fillers constitute the greatest proportion of a formulation, second to the base resin.

The most commonly used fillers are calcium carbonate, alumina silicate (clay) and alumina trihydrate. Calcium carbonate is primarily used as a volume extender to provide the lowest-cost-resin formulation in areas in which performance is not critical.

Alumina trihydrate is an additive that is used for its ability to suppress flame and smoke generation. Fillers can be incorporated into the resins in quantities up to 50% of the total resin formulation by weight (100 parts filler per 100 parts resin).

The usual volume limitation is based on the development of usable viscosity, which depends on the particle size and the characteristics of the resin.

Special purpose additives include ultraviolet radiation screens for improved weatherability, antimony oxide for flame retardance, pigments for coloration and low-profile agents for surface smoothness and crack suppression characteristics.

Mould release agents (metallic stearates, silicon gel or organic phosphate esters etc.) are important for adequate release from the mandrel to provide smooth surfaces and low processing friction.

3.3.5 Winding Methods

There are two different winding methods : (i) wet winding, in which the fibres are passed through a resin bath and wound onto a rotating mandrel (ii) prepreg winding, in which the preimpregnated fibre tows are placed on the rotating mandrel.

Among these winding methods, wet winding is more commonly used for manufacturing fibre reinforced thermosetting matrix composite cylinders.

Compared with prepreg winding, wet winding has several advantages: low material cost; short winding time; and the resin formulation can be easily varied to meet specific requirements. The reviews covered in this article are limited to wet filament winding process and the term "filament winding" is thus referred to the wet winding process hereafter.

3.3.6 Winding Patterns

In filament winding, one can vary winding tension, winding angle and/or resin content in each layer of reinforcement until desired thickness and strength of the composite are achieved. The properties of the finished composite can be varied by the type of winding pattern selected. Three basic filament winding patterns are:

i) Hoop Winding: It is known as girth or circumferential winding. Strictly speaking, hoop winding is a high angle helical winding that approaches an angle of 90 degrees. Each full rotation of the mandrel advances the band delivery by one full bandwidth as shown in Figure 3.2.

ii) Helical Winding: In helical winding, 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 figure (3.3)

iii) Polar Winding: In polar winding, the fibre passes tangentially to the polar opening at one end of the chamber, reverses 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 the mandrel arm rotates about the longitudinal axis as shown in figure (3.4). It is used to wind almost axial fibres on domed end type of pressure vessels.

On vessels with parallel sides, a subsequent circumferential winding would be done.

In 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 patterns. Usually, all composite tubes and pressure vessels are produced by means of helical winding.

4. Recent advances in Filament Winding Technology

Now a days, most of the filament winding machines are numerically controlled with higher degrees of freedom for placing the fibres at required position for meeting the complex design configurations of the products.

Fibre orientation is the decisive factor in the strength of the composites. MATERIAL S.A of Brussels, Belgium has developed a user friendly pattern generation software: CADWIND for obtaining custom fibre orientation and high quality of filament wound components.

CADWIND calculates from the given strength requirements, the fibre lay-up on the mandrel and generates automatically the part program for any winding machine. The laminate structure is reproduced on the winding machine exactly as calculated by CADWIND.

The CADWIND design software tool creates 3D mandrel models and also interface for input of mandrel models from CAD systems .It also calculates the required laminate for axis symmetric and non-axis symmetric mandrel geometries and stores the laminate structure as an interface for finite element method programs.

Optimization of winding angle variation is possible with this software tool. Computer numerical controlled multi-axis filament winding machines using CADWIND software can wind any irregular shapes with no axis of symmetry. Some diagrams of filament wound products are shown below :

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.0 Mechanical Properties of Filament Wound Products

Table 5.1: Typical properties of filament wound pipes (glass fibre reinforced) :

Property

Typical Values

Predominant Process Variables*
Density

1.88-2.26

Glass/Resin Ratio
Tensile Strength, MPa
(Helical Windings)

344-1034

Glass Type, Glass/Resin Ratio, Wind Pattern
Compressive Strength, MPa
(Helical Windings)

276-551

Glass/Resin Ratio, Resin Type, Wind Pattern
Shear Strength, MPa:
--Interlaminar

--Cross

21-137

55-206

Resin Type, Wind Pattern, Glass/Resin Ratio, Resin Type
Modulus of Elasticity (Tension), GPa

21-41

Glass type, Wind Pattern
Modulus of Rigidity (Torsion), GPa

11-14

Wind Pattern
Flexural Strength

344-517

Wind Pattern, Glass/Resin Ratio
*The Predominant Process Variables are those, which have the greatest influence upon the range in the particular values reported.

Table: 5.2: Property comparison: Filament wound composite vis-à-vis others

Material *

Density (g/cc)

Tensile Strength
(MPa)

Tensile Modulus
(MPa)

Specific Tensile
Strength
(103 m)

Filament Wound Composite

1.99

1034

31.02

52.96

Aluminium 7075-T6 2.76

565

71.01

20.87

Stainless Steel -301 8.02

1275

199.94

16.20

Titanium Alloy (Ti-13 V-12 Cr-3 Al) 4.56

1275

110.3

28.50

*For unidirectional composites, the reported modulus and tensile strength values are measured in the direction of fibers.
(Source: C-K Composites, Mount Pleasant, PA)

Table 5.3: Filament wound products: Applications Vs. Resin systems used

Industry

Typical Application

Typical Resin Systems

Corrosion • Underground Storage Tanks
• Aboveground Storage Tanks
Polyester (Ortho- and Iso-phthalic), Vinyl Ester
• Piping Systems
• Stack Liners
• Ducting Systems
Polyester (Ortho- and Iso-phthalic), Vinyl Ester, Epoxy, Phenolic
Oilfield • Piping Systems
• Drive Shafts
• Tubular Structures
Epoxy, Phenolic
Paper and Pulp • Paper Rollers
• Piping Systems
• Ducting Systems
Vinyl Ester, Epoxy
Infrastructure and Civil Engineering • Column Wrapping
• Tubular Support Structures
• Power Poles
• Light Standards
Polyester (Ortho- and

Iso-phthalic), Vinyl Ester, Epoxy

Commercial Pressure Vessels • Water Heaters
• Solar Heaters
• Reverse Osmosis Tanks
• Filter Tanks
• SCBA (Self-Contained Breathing Apparatus) Tanks
• Compressed Natural Gas Tanks
Polyester (Ortho- and

Iso-phthalic), Vinyl Ester, Epoxy

Aerospace • Rocket Motor Cases
• Drive Shafts
• Launch Tubes
• Aircraft Fuselage
• High Pressure Tanks
• Fuel Tanks
Epoxy, Bismaleimide (BMI), Phenolic, Vinyl Ester
Marine • Drive Shafts
• Mast and Boom Structures
Epoxy
Sports and Recreation • Golf Shafts
• Bicycle Tubular Structures
• Wind Surfing Masts
• Ski Poles
Epoxy

6.0 International Trends

The filament winding technology has established itself worldwide due to its precise manufacturing quality and ease in operation compared to other techniques.

The filament wound components, widely accepted in most of the developed countries, are now fast catching up in other parts of the world.A survey of international patents was carried out to understand the latest technology trends. These are summarized in the following sections:

  • A US Patent (# 20030052212) of 2003 by Anderson, describes an invention related to apparatus and methods for winding filament to create a structure. The innovation includes the application of filament to a rotating mandrel to create desired simple and complex shapes.
  • A US Patent (# 6,565,793) of 2003 by Goldworthy, describes the methods of fabricating composite pressure vessels by filament winding process. The process of fabricating a composite vessel includes the steps of: a) fabricating a thermoplastic liner for the vessel; B) overlaying a layer comprising fibre and a thermoplastic material (preferably by winding filaments, rovings or yarns) onto the thermoplastic liner to obtain a composite intermediate structure. Heat and force are applied, until the thermoplastic liner and the overlaid layer consolidate to form a composite vessel, cooling is done until the composite vessel is solidified. Suitable materials for the thermoplastic material include: polyethylene, polypropylene, polybutylene terephthalate and polyethylene terephthalate. The resulting composite vessel exhibits superior mechanical properties.
  • A US Patent (# 6,464,591) of 2002 by Nakajima, describes the fabrication of a power transmission shaft by winding a membrane, film, foil or thin sheet in layers and comprising a longitudinal middle portion composed of FRP layers alone. The shaft has a transitional portion disposed between the middle portion and each end - this is composed of FRP layers; the end portions are composed of metal layers alone.
  • A US Patent (# 5,996,635) of 1999 by Hegler describes the method of manufacturing composite pipe with a socket .A composite pipe comprises an internal pipe and a corrugated external pipe and a socket formed in one piece.
  • A US Patent (# 5,765,600) of 1998 by Newaz, describes the pipe designs using composite materials. It explains the methods for producing improved pipe structures for natural gas distribution pipelines by incorporating a thin fibrous jacket or layer, which can inhibit and prevent cracks in natural gas distribution piping by preventing surface scratches as well as by improving the pipe strength. Thermoplastic fibres are preferred to facilitate the use of joining techniques and hot-tapping techniques common in the natural gas distribution industry.
  • A US Patent (# 3,948,292) of 1976 by Goto, describes production of laminated composite pipe employing a pre-formed pipe as a core and applying a layer of reinforcing fibre onto the outer surface of the core which is being lowered vertically in the direction of its length through a hopper and a tubular outer mould. Resin supplied to the hopper is drawn into an annular space between the wound pipe and the outer mould and forms a layer on the wound pipe core. A flexible pipe may be used as the core, together with a resin that can be subsequently cured, thereby forming a flexible laminated composite pipe which can be covered with a parting tape, stored in reel form, and given a permanent set after installation by curing the resin. Depending upon the nature of the resin employed and upon the number of resin layers applied to the pipe core, reinforcing, insulating and stiffening properties, or any combination of such properties, may be imparted to the composite pipe.
  • A US Patent (# 5,143,374) of 1992, by Shibasaki, describes the fabrication of golf shaft by filament winding process. A golf club shaft includes a tubular inner and outer layers formed out of fiber reinforced composite. In its fabrication, the first fiber group is wound at a first winding angle within the range of 20 - 45 degrees relative to the longitudinal shaft axis. The secondary winding is performed over the first fibre group at a winding angle within the range of 5 - 30 degrees. This type of winding provides excellent structural strength since the outer and inner layers are integrally bonded together.

From the above study and observations, it is identified that filament winding has greater importance to bring out novel products for meeting the industry requirements. Worldwide many industries have been engaged in fabricating filament wound products.

7.0 Indian Scenario

    In view of the crucial need for developing indigenous capability in composite technology, the Advanced Composites Programme was launched by the Department of Science & Technology (Govt. of India). Based on the direct exposure of Technology Information, Forecasting & Assessment Council (TIFAC) to composite applications, the responsibility of implementing the programme was assigned to TIFAC.

    The programme has been an attempt to enhance the utilisation & application of composite as an important performance material in various sectors and to improve upon the laboratory-industry linkages towards development & commercialisation. The programme has been an experiment to bring about a culture of technology development towards commercialization especially for the technology starved SMEs.

    Assessing the importance of filament winding technology for novel applications, the following projects have been launched under the Advanced composite Programme in collaboration with industry partners.

    7.1 Project on Development of composite pressure vessels"

The project was launched in March 2002 under the Advanced Composites Programme of TIFAC in partnership with M/s. Kineco Pvt. Ltd., Panaji and with technology support from IIT-Bombay. The project aimed at developing filament wound pressure vessels for the following applications:

  • Undercarriage FRP tanks (450 mm dia. with 2.00 bar operating pressure to be fitted to the railway passenger coaches for water supply to the toilets
  • Two sizes of pressure vessels (500 mm & 600 mm dia.) for water treatment application; operating pressure : 3.50 bar

All the above vessels were designed as per BS 4994. For fabricating composite pressure vessels with dished/hemispherical ends, need for a multiple axes filament winding facility was found essential. As an integral part of the project, development of a multiple axes CNC filament winding facility was taken up by CNC Technics Pvt. Ltd., Hyderabad for the first time in the country.

Within a short period of 8 months, 4-axes (with one additional X-axis) CNC filament winding system has been designed, developed, fabricated and installed at Kineco, Panaji.The system has the following unique features :

  • The filament-winding machine is powered & controlled by SIEMENS 840 D control system.
  • Pressure vessels/pipes with diameter ranging from 50 mm – 4.00 mts can be wound on the system.
  • Length of the job being wound can vary from 1.00 mts – 9.50 mts
  • While the first spindle can wind diameters ranging from 50 mm – 1500 mm at high rotational speed, the second spindle can rotate diameters up to 4.00 mts at relatively slower speeds. The second spindle can hold component and mandrel weight up to 6.00 tonnes.
  • The unique design of the cross axis allows the winding pattern to be unaltered from 50 mm – 4.00 mts dia
  • The main filament winding carriage feeding the impregnated glass fibre moves at a very high speed of 60 mts per minute
  • The creel stand for fibreglass rovings accommodates 24 spools and has adjustable mechanical tensioning device at its spool. The tension can be accurately controlled for each roving.
  • The drum type resin bath with micrometric adjusting doctor’s blade can control resin pick-up accurately. Top wetting rollers assure proper wetting of rovings and squeeze blades remove excess resin. A temperature controller and a hot water pump controls the resin bath temperature within ± 20 C enhancing the pot life of epoxy resins
  • The CNC control system is enclosed in a fully sealed panel, which has a piggyback air conditioner and can work in any environment.
  • The multi-axis filament winding system is equipped with CADWIND software to facilitate various design configurations of composite parts.

7.2 Project on "Development of Filament wound Glass Reinforced Epoxy (GRE) Pipes"

Presently, the composite pipes are being fabricated using glass fibre and polyester resin matrix by hand lay-up and also by 2-axis filament winding machine .The polyester based pipes are generally mechanically weaker than those made with epoxy resin and their temperature resistance is also lower.

Epoxy pipes would replace traditional pipes in oil transportation where resistance to crude oil and paraffin build up as well as ability to withstand relatively high pressures are required. Due to good chemical resistance, epoxy pipes became popular internationally in chemical process industry as well.

Epoxy pipes would also provide an economical solution to many severe corrosion problems in pulp-mill bleach plants, Phosphoric acid production, food processing industry etc.

In view of the wide application potential of GRE pipes, a project on the development of glass reinforced epoxy (GRE) pipes by filament winding technique is being considered by TIFAC. The GRE pipes would be developed as per ASTM standards, using indigenously developed 4- axes CNC filament winding system for catering to high pressure applications with operating pressure of 32 atm and surge pressure of 40 atm with temperature ranging from sub zero to 110 0C.

It is proposed to develop a wide range of GRE pipings varying between 15 - 1500 NB with lengths up to a maximum of 12 mts. Apart from the light weight and flame retardance, the GRE pipe would offer resistance to highly corrosive fluids at various pressures, temperatures, adverse soil and weather conditions.

These pipes could be effectively used in oil refineries, offshore flat forms, desalination, chemical/pharmaceutical plants, sewerage, heating, cooling fluid lines etc.

7.3 Project on "Development of Filament Wound Composite Pipe Fittings"

At present, the FRP pipefittings 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 & resultant mechanical properties, the service life of such pipefittings is also minimal. By fabricating composite pipefittings using multi axis filament winding system, the fibre lay up pattern would be precise and uniform with optimal consumption of resin & glass fibre.

Using multi axis filament winding system, fitting can be fabricated in any complex configurations suitable for wide range of application areas.

In view of application potential of filament wound pipefittings, a project on development of filament wound composite pipefittings is being considered by TIFAC. Under the project, it is proposed to fabricate composite pipefittings as per ASTM standards using indigenously developed 6-Axis CNC Filament winding system along with high-end software.

The FRP pipe fittings, finds application in oil exploration & transportation, refineries, chemical & pharmaceutical plants desalination & water treatment plants, irrigation, nuclear & thermal power plants, sewerage, fire fitting, food processing, ducts etc.

8. Conclusion

The filament wound composite pipes are better replacement for all steel and metal pipelines in oil, gas and water supply systems, which are corrosive in nature. There is a substantial need to renovate and revamp all the municipal pipelines for water & sewerage transportation with composites, which are durable, non-corrosive and reduced pipeline failures even at high pressures.

Composite technology and applications have made tremendous progress globally during the last two decades or so, as evident from the present level of consumption of composite materials at about 2.2 million MT in the world, with the Asia-Pacific region accounting for about 24% of this usage.

Currently, about 40,000 composite products are in use for an array of applications in diverse sectors of the industry all over the world. While China and India started making use of composites almost simultaneously about 30 years ago, the progress made by china is rather astounding with an annual consumption level of about 2,00,000 MT, as compared to about 30,000 MT in India.

Multiple commercial applications for composites and potential for export have not been tapped even in a limited way in the country. Commercializing this technology would bring out a steady growth in our economy.

India with an excellent knowledge base in various resins, catalysts & curing systems coupled with an adequate availability of various raw materials can certainly carve out a niche in the emerging technology of composite fabrication.

The indigenous capabilities in designing & developing advanced composite fabricating machinery would go a long way in generating a significantly higher usage of composites both for domestic consumption and for overseas market.

For further information, please contact Mr. S. Biswas at This e-mail address is being protected from spambots. You need JavaScript enabled to view it