Filament winding

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Filament winding is a fabrication technique mainly used for manufacturing open (cylinders) or closed end structures (pressure vessels or tanks). This process involves winding filaments under tension over a rotating mandrel. The mandrel rotates around the spindle (Axis 1 or X: Spindle) while a delivery eye on a carriage (Axis 2 or Y: Horizontal) traverses horizontally in line with the axis of the rotating mandrel, laying down fibers in the desired pattern or angle to the rotational axis. The most common filaments are glass or carbon and are impregnated with resin by passing through a bath as they are wound onto the mandrel. Once the mandrel is completely covered to the desired thickness, the resin is cured. Depending on the resin system and its cure characteristics, often the mandrel is autoclaved or heated in an oven or rotated under radiant heaters until the part is cured. Once the resin has cured, the mandrel is removed or extracted, leaving the hollow final product. For some products such as gas bottles, the 'mandrel' is a permanent part of the finished product forming a liner to prevent gas leakage or as a barrier to protect the composite from the fluid to be stored.

Contents

Filament winding is well suited to automation, and there are many applications, such as pipe and small pressure vessel that are wound and cured without any human intervention. The controlled variables for winding are fibre type, resin content, wind angle, tow or bandwidth and thickness of the fiber bundle. The angle at which the fibre is wound has an effect on the properties of the final product. A high angle "hoop" will provide circumferential strength, while lower angle patterns (either polar or helical) will provide greater longitudinal / axial tensile strength.

Products currently being produced using this technique range from pipes, golf club shafts, reverse osmosis membrane housings, oars, bicycle forks, bicycle rims, power and transmission poles, pressure vessels, missile casings, aircraft fuselages, lamp posts and yacht spars.

Filament winding machines

The simplest winding machines have two axes of motion, the mandrel rotation and the carriage travel (usually horizontal). Two axes machines are best suited to the manufacture of pipes only. For pressure vessels such as LPG or CNG containers (for example) it is normal to have a four axis winding machine. A four axes machine additionally has a radial (cross-feed) axis perpendicular to carriage travel and a rotating fibre payout head mounted to the cross-feed axis. The payout head rotation can be used to stop the fibre band twisting and thus varying in width during winding.

Machines with more than four axes can be used for advanced applications, six-axis winding machines usually have 3 linear and 3 rotation axes. Machines with more than 2 axes of motion have computer/CNC control, however these days new 2-axis machines mostly have numeric control. Computer controlled filament winding machines require the use of software to generate the winding patterns and machine paths, such software can normally be provided by filament winding machine manufacturers or by using independent products such as Cadfil [1] or Cadwind, [2] a review of programming techniques for CNC machines can be found in. [3] An example of such a winding process can be found all throughout the web.

Process

The process of Filament Winding;

Filament winding processes can be either Continuous or Discontinuous type.

Continuous winding Process

Continuous winding processes are used to manufacture low pressure, small to very large diameter pipes continuously on a mandrel formed out of an endless band (commonly known as the Drostholm Process). Pipes manufactured through this process are primarily used for media (water, sewage, waste-water) transmission / distribution networks. Continuous filament winding machines are usually 2 axis machines capable of laying fibre, fiberglass cloth, veil in a continuous hoop pattern. These machines are usually equipped with multiple chopper motors (to impart multi directional fibre placement on the part) and sand hoppers (to drop sand onto the part and impart a structurally strengthened core)

Discontinuous Winding Process

Discontinuous winding process is used to manufacture high pressure parts, pipes, pressure vessels and complex components. Multi axes machine are used to customize the angle of lay for the fiberglass band.

Other Filament Winding Equipment

Fiberglass impregnation

Fiberglass direct rovings are immersed in a resin bath where they are coated with resin system. Each strand in the fiberglass roving is coated with sizing chemistry that provides secondary bonding between the fiberglass strand and the resin. Sizing can be singular resin system compatible (like polyester compatible or epoxy compatible) or multi-system compatible (polyester+epoxy+polyurethane compatible). Compatibility of the sizing is critical in ensuring a bond between the resin and fiber except in the case of polyurethane resin systems where the resin bonds directly to the glass as well as the sizing equally well. Conventional Resin impregnation systems are the "W Dip Bath" or the "Doctoring Roll" design, however recently there have been major advances in the impregnation bath to reduce waste, maximize resin impregnation effectiveness and improve composite matrix properties. [5] This results in far superior impregnation and resin to glass ratio control as compared to the conventional baths.

The impregnated tows are then literally wound around a mandrel (mold core) in a controlled pattern to form the shape of the part. After winding, the resin is then cured, typically using heat. The mold core may be removed or may be left as an integral component of the part(Rosato, D.V.). This process is primarily used for hollow, generally circular or oval sectioned components, such as pipes and tanks. Pressure vessels, pipes and drive shafts have all been manufactured using filament winding. It has been combined with other fiber application methods such as hand layup, pultrusion, and braiding. Compaction is through fiber tension and resin content is primarily metered. The fibers may be impregnated with resin before winding (wet winding), pre-impregnated (dry winding) or post-impregnated. Wet winding has the advantages of using the lowest cost materials with long storage life and low viscosity. The pre-impregnated systems produce parts with more consistent resin content and can often be wound faster.

Fiberglass Tensioners

Fiber tension is a critical element in building composite structures. If tension on the strand is too low, the composite laminate structure will have lower mechanical strength and performance. If the tension is too high, the strands may experience fraying of the stands or fuzz buildups.[ clarification needed ] Due to excessive tension, the resin to glass ratio in the laminate may also increase to beyond an acceptable limits resulting in laminates that are unsuitable in applications that transport media and liquids.[ clarification needed ]

Fiberglass tensioners[ clarification needed ] may impart dry or wet tension depending on its location, prior to or post impregnation of the fiberglass strands.

Materials

Glass fibre is the fibre most frequently used for filament winding, carbon and aramid fibres are also used. Most high strength critical aerospace structures are produced with epoxy or polyurethane resins, with either epoxy, polyurethane or cheaper polyester resins being specified for most other applications. The ability to use continuous reinforcement without any breaks or joins is a definite advantage, as is the high fibre volume fraction that is obtainable, about 60% to 80%. Only the inner surface of a filament wound structure will be smooth unless a secondary operation is performed on the outer surface. The component is normally cured at high temperature before removing the mandrel. Finishing operations such as machining or grinding are not normally necessary (Furness, J., Azom.com).[ citation needed ]

Hazards

Emissions

Employees in fibreglass manufacturing processes using polyester and vinyl ester resin systems are exposed to multiple hazards – high levels of styrene. [6] As styrene emission controls and limits get tighter, the industry is shifting slowly towards resin systems like polyurethanes that do not have volatile solvents.[ citation needed ]

Bisphenol A

Bisphenol A (BPA) is a key component of epoxy resin systems. BPA is a suspected endocrine disruptor and is banned in many countries from being used in products like baby bottles. Because BPA is a reproductive, developmental, and systemic toxicant in animal studies and is weakly estrogenic, there are questions about its potential impact particularly on children’s health and the environment. US-EPA intends to initiate alternatives analyses for BPA in BPA-based materials lining water and waste water pipes since this application may have a potential for human and environmental exposure. [7] BPA from epoxy-based composite products like pipes can leach out into the fluid medium (water)when subjected to elevated temperature and is a cause of concern.[ citation needed ]

Toxic and Hazardous Curatives

Related Research Articles

Fiberglass or fibreglass is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic.

<span class="mw-page-title-main">Epoxy</span> Type of material

Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also collectively called epoxy. The IUPAC name for an epoxide group is an oxirane.

<span class="mw-page-title-main">Thermosetting polymer</span> Polymer obtained by irreversibly hardening (curing) a resin

In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure or mixing with a catalyst. Heat is not necessarily applied externally, and is often generated by the reaction of the resin with a curing agent. Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.

<span class="mw-page-title-main">Lamination</span> Technique of fusing layers of material

Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing materials, such as plastic. A laminate is a permanently assembled object created using heat, pressure, welding, or adhesives. Various coating machines, machine presses and calendering equipment are used.

Fibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, aramid, or basalt. Rarely, other fibres such as paper, wood, boron, or asbestos have been used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, though phenol formaldehyde resins are still in use.

<span class="mw-page-title-main">Mandrel</span> Gently tapered cylinder against which material can be forged or shaped

A mandrel, mandril, or arbor is a tapered tool against which material can be forged, pressed, stretched or shaped, or a flanged or tapered or threaded bar that grips a workpiece to be machined in a lathe. A flanged mandrel is a parallel bar of a specific diameter with an integral flange towards one end, and threaded at the opposite end. Work is gripped between the flange and a nut on the thread. A tapered mandrel has a taper of approximately 0.005 inches per foot and is designed to hold work by being driven into an accurate hole on the work, gripping the work by friction. A threaded mandrel may have a male or female thread, and work which has an opposing thread is screwed onto the mandrel.

Gelcoat or gel coat is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite. The most common gelcoats are thermosetting polymers based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state. They are cured to form crosslinked polymers and are subsequently backed with thermoset polymer matrix composites which are often mixtures of polyester resin and fiberglass, or epoxy resin which is most commonly used with carbon fibre for higher specific strength.

Pultrusion is a continuous process for manufacture of fibre-reinforced plastics with constant cross-section. The term is a portmanteau word, combining "pull" and "extrusion". As opposed to extrusion, which pushes the material, pultrusion pulls the material.

Polyester resins are synthetic resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Maleic anhydride is a commonly used raw material with diacid functionality in unsaturated polyester resins. Unsaturated polyester resins are used in sheet moulding compound, bulk moulding compound and the toner of laser printers. Wall panels fabricated from polyester resins reinforced with fiberglass—so-called fiberglass reinforced plastic (FRP)—are typically used in restaurants, kitchens, restrooms and other areas that require washable low-maintenance walls. They are also used extensively in cured-in-place pipe applications. Departments of Transportation in the USA also specify them for use as overlays on roads and bridges. In this application they are known AS Polyester Concrete Overlays (PCO). These are usually based on isophthalic acid and cut with styrene at high levels—usually up to 50%. Polyesters are also used in anchor bolt adhesives though epoxy based materials are also used. Many companies have and continue to introduce styrene free systems mainly due to odor issues, but also over concerns that styrene is a potential carcinogen. Drinking water applications also prefer styrene free. Most polyester resins are viscous, pale coloured liquids consisting of a solution of a polyester in a reactive diluent which is usually styrene, but can also include vinyl toluene and various acrylates.

Sheet moulding compound (SMC) or sheet moulding composite is a ready to mould glass-fibre reinforced polyester material primarily used in compression moulding. The sheet is provided in rolls weighing up to 1000 kg. Alternatively the resin and related materials may be mixed on site when a producer wants greater control over the chemistry and filler.

Spray-Up also known as chop method of creating fiberglass objects by spraying short strands of glass out of a pneumatic gun. This method is used often when one side of the finished product is not seen, or when large quantities of a product must be made cheaply and quickly with moderate strength requirements. Corvette fenders and boat dinghies are commonly manufactured this way.

A thermoset polymer matrix is a synthetic polymer reinforcement where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements. They were first developed for structural applications, such as glass-reinforced plastic radar domes on aircraft and graphite-epoxy payload bay doors on the Space Shuttle.

Carbon fiber-reinforced polymers, carbon-fibre-reinforced polymers, carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic, also known as carbon fiber, carbon composite, or just carbon, are extremely strong and light fiber-reinforced plastics that contain carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications.

Fiberglass reinforced plastic grating is a composite material manufactured by combining a matrix of resin and fiberglass. Fiberglass grating does not corrode like steel grating and is therefore used in corrosive environments to reduce maintenance costs. It is used in a variety of applications including walkways and overhead platforms. FRP grating is a structural product that can be weight-bearing between spans.

<span class="mw-page-title-main">Continuous filament winding machine</span>

A continuous filament winding machine is a machine for laying filament windings continuously over a cylindrical steel band. The steel band is carried on a forward moving mandrel which is able to collapse and return to the beginning of the travel. The steel band is released after the mandrel collapses and is continuously fed back to the start of the travel where it is again wound on to the mandrel.

Automated fiber placement (AFP), also known as advanced fiber placement, is an advanced method of manufacturing composite materials. These materials, which offer lighter weight with equivalent or greater strength than metals, are increasingly used in airframes and other industrial products.

A discontinuous filament winding machine is a machine for laying fiberglass filament windings over a cylindrical mould or mandrel bar using a carriage that is traveling along the axis of that mandrel. The mandrel is fixed on a mandrel stand and is rotated by an asynchronous motor. The carriage is the set-up that holds and winds the fiberglass on the rotating mandrel. The difference between the continuous and discontinuous filament winding machine is the area on which filament winding is laying out.

<span class="mw-page-title-main">Flowtite Technology</span>

Flowtite Technology AS is a Norwegian technology company, owned by Amiantit Group. It develops GRP pipe manufacturing technology and designs tailor-made manufacturing equipment under the brand name Flowtite. Its predecessor, Vera Fabrikker, was the first company in the world to utilize a continuous filament winding machine for production of glassfibre-reinforced plastic pipes and to invent the corresponding manufacturing process, commonly known as continuous filament winding process or Drostholm process.

CFSMC, or Carbon Fiber Sheet Molding Compound, is a ready to mold carbon fiber reinforced polymer composite material used in compression molding. While traditional SMC utilizes chopped glass fibers in a polymer resin, CFSMC utilizes chopped carbon fibers. The length and distribution of the carbon fibers is more regular, homogeneous, and constant than the standard glass SMC. CFSMC offers much higher stiffness and usually higher strength than standard SMC, but at a higher cost.

In materials science, a polymer matrix composite (PMC) is a composite material composed of a variety of short or continuous fibers bound together by a matrix of organic polymers. PMCs are designed to transfer loads between fibers of a matrix. Some of the advantages with PMCs include their light weight, high resistance to abrasion and corrosion, and high stiffness and strength along the direction of their reinforcements.

References

  1. ↑ Advanced Filament winding software
  2. ↑ Cadwind filament winding software
  3. ↑ Stan Peters, "Composite Filament Winding", 2011 , ch 4, ISBN   1615037225
  4. ↑ Todd, Robert H. "Manufacturing Processes Reference Guide." Industrial Press Inc. New York. 1994. Pg. 228
  5. ↑ "Urethane Composites Group LLC". Archived from the original on 2019-05-28. Retrieved 2017-11-08.
  6. ↑ http://www.doli.state.mn.us/pdf/fiberglass.pdf [ bare URL PDF ]
  7. ↑ BPA Action Plan - US EPA
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