Pultrusion applications – a world-wide review

6 Pultrusion applications – a world-wide review TREVOR F STARR

6.1

Introduction

The technical development, commercialisation and market growth of pultruded profiles from kite rods and electrical slot wedges, through ladders and simple cross-sections to true structural elements of increasingly massive section is one of the success stories of the now mature composites industry. There are many reasons. Product criticality is the main reason, whether in respect of the superior and consistent mechanical–physical property performance or close dimensional tolerances, coupled to an excellent surface finish that can be attained whatever the profile complexity. Both the cost-effective and high environmental/chemical-resistant benefits must be added, which typically accrue from the correct formulation, specification and use of composites irrespective of the fabrication technique employed. All are features ably demonstrated by the profiles whose selection and following description also highlights in many other positive ways why pultruded profiles are of increasing attraction to the designer, specifier, consulting engineer, architect or purchase manager. The offshore oil/gas industry application alone confirms why timber, metal, thermoplastic and sometimes reinforced concrete are in their respective ways often no longer the optimum material answer for the manufacture of engineering sections or profiles to be used as structural elements. With such a diversity of case-history excellence, any selection, which must perforce be limited, is also invidious. Many companies other than those gratefully acknowledged for the provision of the illustrations could, through other very suitable example, have equally been featured. At the same time any suggestion of an importance in the order of listing has been countered by recourse to classifications based simply on the alphabet. However, even that classification employing named or market-application examples was not without difficulty. With justification, several could feature again under a different heading. 197

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6.2

Airport

The lightweight, structural, electrical resistant and easily erected properties of pultruded profiles come to the fore in the design of a wide range of aerial and lighting support assemblies which play their equal part in securing the safety of air travel. In addition their ability to be readily designed and constructed on-site from the wide selection of standard glass–polyester rather than custom-moulded profiles now available, plus built-in self-colour decoration and low maintenance benefits, all add further advantages. As a further important consideration, should the worst happen, then the flexible nature of pultruded profiles’ individual structural elements presents a much lower hazard than would otherwise be the case for a steel or even aluminium alternative, the design of which also had to allow for insulators of one type or another. Such constructions typically satisfy the Federal Aviation Authority specification AC 150/5345-45A and, although sufficiently rigid to accept strong winds and heavy ice-loads, are frangible as stipulated by ICAO ADM6. As a result of, for example, the patented cross-bar joint-bonding method developed by the Finnish pultruder Excel Oy, there is no twisting, swaying or oscillation within the structure, which in the case of approach lighting support masts (Fig. 6.1) would otherwise cause serious distortion of the light beam and its pattern presented to the pilot. In service since 1990, well over 50 complex, successful installations have now been completed by that same company who can add to all those advantages the clear finding that there is no need for periodic realignment and/or tightening of the fixing system that are found necessary with certain types of aluminium masts. Many of the same advantages apply to the growing use of pultruded profiles for the construction of heavy duty, maintenance-free airport fencing systems that to vital importance are also radar transparent. At the same time they do not disrupt the optimum working of the Instrument Landing System (ILS). One fence design by the Belgium company Bekaert employs an internal fixing system that prevents easy removal of the separate panels from which it is constructed and, being free of cross bars and topped with a sharp sawtoothed finish, makes for an extremely difficult obstacle to climb (Fig. 6.2). The manufacturer claims that around 100 m (325 ft) of fence can be erected by two men per day and that the design can be readily up-graded in those areas where there may be exposure to jet engine blasts of 300 km (185 miles) per hour. While the support elements typically embedded in concrete might well employ a vinyl ester as the matrix, a good-quality isophthalic polyester has been found eminently suitable for the remainder of the structure, all items being solely glass fibre reinforced.

6.1 Typical airport approach lighting assemblies (Courtesy, Exel Oy, Finland)

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6.2 Pultruded profile airport fencing system (Courtesy, Bekaert Composites, Belgium)

6.3

Cableways

The electrical resistance properties for which composites are generally noted has prompted the extensive use of pultruded profiles in the design of cableway support or cable tray systems. These range from those assembled from rod or tube with suitable jointing pieces (Fig. 6.3) to a wide range of custom-moulded design to satisfy in an optimum manner the weight, size and number of electrical, telephone and perhaps even optical data transmission lines that are required to be securely carried over what may be both a long and undulating distance. Additional properties such as special environmental, fire or chemical-corrosion resistance may also be very frequently specified. Among what are perhaps scores of pultruded cableway designs, the work of the Italian pultrusion company Top Glass SpA and the UK company Fibreforce Ltd is worthy of note as joint suppliers meeting the exacting standards of the cable trays employed in the Channel Tunnel. The main profiles produced for this project are shown in Fig. 6.4 with Fig. 6.5 illustrating one manufactured length of the five-way design and its installation with other cable tray designs within the tunnel.

Pultrusion applications – a world-wide review

6.3 Cableway assembled from pultruded profiles and additional moulded fixtures

Five-way cable tray 450X100 mm2 (17.7” X 4”)

Two-way cable tray 600X200mm2 (24” X 7.8”)

For telephone, sound, radio and fibre optic cables located in service tunnel

For high-power cables in main tunnels

6.4 Channel Tunnel cable way profiles (Courtesy, Top Glass SpA)

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6.5 Channel Tunnel profiles and installation (Courtesy, Top Glass SpA)

Pultrusion applications – a world-wide review Table 6.1.

203

Mechanical and fire performance, Channel Tunnel cable tray profile

Fire properties

Limit

Result

BS 476 Pt 6 Fire Propagation

I<6 I < 12

0.5 11.8

BS 476 Pt 7 Surface Spread of Flame

Class 1

Class 1a

BS 6853 Smoke Evolution (Rolling Stock Design)

A0 On < 4 Off < 6

2.3 2.5

BS 6853 Temperature Index (Flammability)

>350 °C (>660 °C)

>350 °C (>660 °C)

NFF 16–101 Fire Behaviour

M2 FO

M1 FO

NES 713 Toxic Fume Index

<5 (Ideal Cat 1)

1.2

Toxic gas exclusions/limits

No halogens <100 ppm SO2 <10 ppm NOx

None present Not present Not present

Mechanical properties

Longitudinal

Transverse

Flexural strength (MPa)

535

155

Flexural modulus (GPa)

17.6

12.2

Tensile strength (MPa)

470

46.8

Tensile modulus (GPa)

22.6

12.0

Impact strength (J/m)

4440b 4858c

— —

a

Zero burn. b Notched. c Unnotched. Matrix: MODAR 826HT 100 pbw Antimony trihydrate 170 pbw Data: Ashland Chemicals Inc.

Glass: CFM/Roving/CFM 39% v/v (49%w/w)

Neglecting for a moment the fire performance, the environmental conditions within the tunnel are particularly severe, from the wind speed of 360 km/h (225 mph) created by the frequent passage of trains, to an ambient temperature varying between 10 and 40 °C (50–105 °F) at a humidity level of 100%. In addition steady seawater ingress into the tunnel was another condition that could be accommodated more readily by a composite pultrusion than by galvanised mild steel or exotic grades of stainless steel which were competitive materials considered for the project by Transmarche-Link (TML) and its subcontractors Balfour Kilpatrick and Spie Batignolies. There was concern with both the latter over a high corrosion rate which over a long period of time would lead to unacceptable replacement costs and major rail service disruption. The stringent fire performance requirements were answered by the use

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of an aluminium trihydrate-filled MODAR methacrylate resin matrix (826 HT) as shown – together with mechanical property data – in Table 6.1. In total, the production involved well over 400 km (250 miles) of pultrusion, corresponding to more than 3600 tonnes (7.9 million lb) in weight.

6.4

Cooling towers

Compared with the traditional materials, timber, steel and reinforced concrete formerly employed, the performance advantages of low-weight, high-strength, excellent electrical, corrosion and environmental resistance certainly apply in the construction of cooling tower structures.1 They are applications offering a tremendous development and sales potential for nothing more than, in effect, standard-section glass fibre–polyester resin formulated pultruded profiles. When Barrick Goldstrike Mines, Inc, for example, faced the need to cool water associated with its mining operation in the high desert region of northern Nevada, the optimum environmental answer satisfying the extreme weather conditions of the site was a massive, competitively priced, on-site erected, pultruded construction some 14 m (46 ft) tall, spanning 330 m (1100 ft) and over 16 m (54 ft) wide, manufactured by the American company Bedford Reinforced Plastics. Twenty-nine flat bed trucks were employed to ship to a tight schedule the 278 tonnes (612 000 lbs) of square, angle, channel, deck board and structural members, whose combined length totalled more than 120 000 m (400 000 ft). To the benefit of fabrication and installation lead times, the thousands of bolt connecting holes required were machined prior to shipment, using a computer-controlled router to ensure dimensional consistency and accuracy. The tower (Fig. 6.6) consists of two banks of 10 cells, each capable of reducing the temperature of over 356 000 l (65 000 US gallons) of water per minute from 55 °C (130 °F) down to a temperature equating at all times with that of the local Humboldt River to which it is returned. Making this mandatory regulation even more of a challenge, the temperature of the region varies from -30 °C in winter to 24 °C in summer and while that volume is not a huge amount of water for a tower to handle, it is this thermal duty that has made the project and its composites method of construction unique.

6.5

Fencing

Natural hedges of bush, tree and other foliage make ideal division for the containment of farm and other animals but their costly maintenance, slow growth and inability to be relocated make the use of fencing materials essential. However, most timber, reinforced concrete and metal-based alter-

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6.6 Water cooling tower structure (Courtesy, Bedford Reinforced Plastics)

natives present, in addition to cost, distinct disadvantages such as slow installation which has given rise to the growing and effective use of electric fence systems by the farming industry. These can be quickly moved and although the more cost-effective answer in competition to these traditionals, most commercial systems still continue to employ extruded thermoplastic in the form of small diameter rods or alternative profile sections. Even if those designs contain chopped glass fibre and are of larger section, their major disadvantages are typically limited temperature resistance and insufficient toughness, with the latter property degraded in-service by ultraviolet (sunshine) attack. Taken together they impair their attraction as a sound long-term capital investment for the farmer. On the other hand pultruded glass fibre/polyester fence post rod, 10 mm (0.4 inch) or 13 mm (0.5 inch) in diameter (Fig. 6.7), incorporating several proprietary fence-wire attachment and other devices, overcomes all these disadvantages without introducing any further constraint to a more widespread use than a higher cost (but much better capital investment) in comparison to the thermoplastic alternative. Not only is the former thermoset, with a typical di-electric strength of 12 kV/mm, one of the best insulators, but the material is totally impervious to moisture and is not affected by the extremes of ambient temperature, super-phosphates and chemical sprays. Furthermore, the glass–polyester composite will not readily support the

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6.7 Pultruded fence post system (Courtesy, Pultron Composites Ltd, New Zealand, and Tern Engineering Pte Ltd, Singapore)

Table 6.2. Mechanical properties, pultruded fence posts Tensile strength

400 MPa

Tensile modulus

25 GPa

Flexural strength

450 MPa

Flexural modulus Compressive strength

25 GPa 200 MPa

Courtesy: Tern Engineering Pte Ltd, Singapore.

growth of lichens or for example moss, and if fire performance is an additional requirement in locations where the occurrence of fire is a possibility, then a phenolic-based, glass fibre pultrusion can readily provide an immediate, low-cost answer. This enhanced toughness (Table 6.2) has also permitted the successful extension of these pultruded fence post systems to the containment of even the largest and heaviest animals in the wild, ranging upwards from kangaroos to elephants. For example, while a fence height of perhaps less than 1 m (3.3 ft) is suitable with three horizontal wires for most farm animals, certain predators require around 1.25 m (4 ft) with perhaps seven wires, whereas a three-wire arrangement, nearly 2 m (6 ft) high is necessary for

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elephants: overall an effective, increasingly recognised and valuable new fencing system based on the very simplest of pultruded profiles. There is a clear difficulty in many instances in segregating fence, walkway and staging systems, whether employed for agriculture, chemical processing, water filtration and treatment, or some other use. Reference should therefore be made to later sections dealing specifically with stagings and walkways.

6.6

Flooring and walling systems

The above comment is equally true in connection with flooring, walling and allied systems employing pultruded profiles. These modular, often selfjointing, industrial systems typified by Figure 6.8, are ideal for a wide range of filtration, water-treatment, chemical and corrosive environments. As a result, a number of proprietary systems (e.g. Bio-Planktm from Bi Original as in Figure 6.9 or FlowGRIPtm from Redman Fisher Engineering) are now available. Indeed, their design and development often originates from companies who do not pultrude, thus allowing them the competitive purchase of profiles in specific custom shapes and dimensions, as well those classified as standards.The American concerns, Strongwell and Creative Pultrusions, together with the UK company Fibreforce and Bekaert in Belgium, are among many manufacturers world-wide from which such profiles are

6.8 ‘Bio-Plank’TM modular flooring units employed in water treatment/filtration plant (Courtesy, Fibreforce Ltd)

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sourced. A typical example of this ‘innovative application of GRP pultrusion technology’, as patented by Redman Fisher Engineering (FlowGRIP) employs a 0.5 m (20 inch) wide by 40 mm (1.6 inch) deep integrally coloured interlocking plank with a built-in sealing tongue and groove forming a ‘solid’ surface. Otherwise the design may be slotted to allow rapid drainage, or the respective profile components coated with an anti-skid texture. Designed to give maximum rigidity at minimum weight such pultruded profile constructions are rapidly replacing timber, steel and reinforced concrete. The low shipment weight and ease of erection onto a minimum of foundation work, and an ability, for example, to accept a loading of 13 kN/m2 on a raised 200 m2 (2150 ft2) platform are very desirable attributes, to say nothing of their virtual elimination of an on-going maintenance requirement. Another major advantage is the non-sparking characteristic of the pultruded composite. Many industrial environments cannot tolerate the generation of sparks, and the offshore industry market is therefore of particular and growing importance to the pultrusion industry. If nothing else, the replacement of corroded steel components at offshore production platforms is not only expensive but typically requires a temporary halt to operations through the danger of sparks, etc, during the necessary on-site welding. Room for heavy lifting gear may be another constraint, answered in the case of a 12 ¥ 6 m2 (40 ¥ 20 ft2) composite well-bay platform installed by four men in just two days compared with the eight workmen in five days required for the steel alternative. There is much market-application interaction. Nevertheless it is obvious through many of this chapter’s application examples, that machine-made

6.9 ‘Bio-Plank’TM employed as walling (Courtesy, Bi Original)

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pultruded profiles are steadily opening-up the way for new design thinking that places great benefit on the consistent quality and predictable engineering properties for which such profiles are now increasingly recognised. It is appropriate to include in this particular application review comment pertinent to both fire and component costs. Fire performance receives consideration in other chapters but it is worth reporting that taking just one example, pultruded flat panels successfully passed jet-fire tests conducted by Shell Expro at the British Gas Test Centre. During this tough 2 hour test, the panels were exposed to a high-pressure gas jet burning at around 1200 °C (2200 °F) which was estimated to have consumed some 18 tonnes (40 000 lbs) of gas. As additionally described later, further offshore tests have also confirmed the ability of the composite assemblies to withstand the effects of an offshore explosion. However, virtually ever since their introduction, composite components have been criticised – and indeed too frequently rejected – on account of their admittedly higher supply cost when compared with the other materials with which they daily compete. Any assessment based solely on the supply cost is very seriously in error: a situation that is now being increasingly recognised and accepted. A much more accurate and therefore correct assessment is the in-service life cost, which takes into account such important matters as shipment, installation and the maintenance, environmental cost savings, all of which can be appreciable. Finally, any comment regarding flooring systems cannot overlook the now extensive use of gratings fabricated from pultruded profiles which are typically available from a large number of companies world-wide in 1 m2 (11 ft2) modules and which have a visual appearance not dis-similar from the flooring shown in Fig. 6.8. A reproduction of actual point-load deflections for a typical pultruded grating design is given by Fig. 6.10 and most grating suppliers are in a position to provide similar and additional data including, for example, uniform and linear load conditions. Among all the other examples mentioned, pultruded floor members are finding a growing agriculture acceptance where – in addition to surround fencing – there is a rapid build and later teardown requirement for farm animal containment units of wide dimensional and weight acceptance variation having long-term resistance to what is typically a severely corrosive environment.

6.7

Kolding bridge

Referenced elsewhere in other chapters, the two UK bridges, Aberfeldy and Bonds Mill, employing pultruded profiles have since their construction in the early 1990s become famous. Through their success, they have become recognised as definite percursors for this type of application. However, their combined effect on that market potential has, even though the short

6.10 Point loading data for pultruded grating (Courtesy, Fiberline Composites A/S, Denmark)

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span of Bonds Mill carries road traffic, been somewhat limited simply because custom rather than standard profiles were employed in their construction. It can be argued therefore that the other bridge examples discussed in Chapter 7, but in particular the Kolding bridge2 over a main, double railway track in Denmark, have, as a result of their use of standard, off-the-shelf, glass fiber–polyester resin profiles, had a much greater effect in demonstrating the way forward for this sector of the composites industry (Fig. 6.11). Its success as a 40 m (130 ft) long light vehicle and pedestrian bridge, is a positive example of the increasing penetration by composites generally, of the civil engineering–infrastructure requirement. In addition, Kolding bridge, designed and built by the Danish pultrusion company Fiberline Composites A/S, has secured a number of historical firsts. Not only is it the first for Scandinavia, and also the first to span a railway line and a busy one at that, but it is one of the biggest examples of its type with the performance specification demanding not just safe and quick installation but requiring a

6.11 The Kolding, pultruded profile bridge (Courtesy, Fiberline Composites A/S, Denmark)

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minimum of on-going long-term maintenance. Weighing less than 12 tonnes (26 500 lbs) which is less than half that of a similar steel design, the loadcarrying capacity of 500 kg/m2 (100 lbs/ft2) allows for snow-clearing vehicles, etc, of up to 5 tonnes (11 000 lbs) to pass at the same time. The maximum allowable wheel pressure is 1.8 tonnes (4000 lbs). On-site assembly, which took two nights during weekends when the train traffic was at its lowest, was assisted by the in-factory assembly of three main bridge units – an 18.5 m (60 ft) tower, a 27 m (88 ft) deck section and a 13 m (43 ft) deck section, both 3 m (10 ft) wide – using stainless steel bolts at every connection. Special attention was given to these fixing points to ensure they could withstand both the static and dynamic forces, as well as creep. Sufficient transverse as well as longitudinal performance in each of the required polyester-based profile sections was guaranteed by the careful placing, as necessary within the fibre architecture, of glass fibre woven roving, combination and biaxial materials in addition to unidirectional rovings. It must, however, be noted that certain parts of the wall sections, seen typically perforated in Fig. 6.11, are not pultrusions but rather flatplate glass–polyester mouldings chosen for their cost-effectiveness in this largely non-structural area. Although considerable structural design, development and evaluation work was undertaken well before construction commenced, with the latter continuing as part of the overall quality control procedure, the completed bridge is being carefully monitored by 28 stategically located strain gauges. The results are already providing a wealth of data of value to other designers, constructors and engineers and particularly in the context of a second bridge that Fiberline is hoping to construct in Switzerland. Finally, Table 6.3 provides some comparable cost estimates between pultruded composites, steel and reinforced concrete.

6.8

Leisure

Providing confirmation that pultruded profiles are beginning to penetrate every facet of twenty-first century life and will increasingly do so is ideally exemplified by the extensive use of profiles in the construction of a spectacular re-creation of Italy’s Lake Como as the frontage to the new Bellagio Hotel and Resort in Las Vegas, Nevada (Fig. 6.12). Spanning 400 m (1320 ft) overall and with a capacity of 113 million litres (30 million US gallons), this ‘lake’ and huge fountain display feature a water, light and musical show each night, vying with the many other visual attractions to be found around this leisure city. Although invisible from the surface of the lake, some 182 tonnes (400 000 lbs) of black pigmented structural pultruded profile manufactured by the American pultruder Bedford Reinforced Plastics, supports some

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Table 6.3. Unit breakdown comparing Kolding bridge construction costs, pultrusions, steel and reinforced concrete Composite

Steel

Reinforced concrete

Engineering

60a

30

22

Foundations

60

75

90

120

20

60

90

Installation

30

60

90

Surface treatment

10

30

15

Materials Production assembly

90 Nil

Other

30

40

40

Totals

370

345

347

a

Includes development costs.

6.12 Section of pultruded profile sub-structure in Lake Como feature at Bellagio Hotel and Resort, Las Vegas (Courtesy, Bedford Reinforced Plastics, USA)

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3500 m2 (38 000 ft2) of composite grating supplied through Seasafe of Lafayette, Louisiana and Grating Systems of Ogden, Utah. That grating is employed in turn to support the entire fountain and lighting display, and this continuously submerged pultruded-grating substructure, typically 0.6 m (2 ft) below the lake surface, exhibits a length of around 800 m (2600 ft), at a maximum width of just over 3.6 m (12 ft) and a height of almost 4 m (13 ft). At that depth and because of the black pigmentation, none of that substructure is visible when the fountain and light-show are not operating and the lake is caused to model the usual placid appearance of Lake Como. Claimed to be the largest pultruded structure yet built, the basic construction is, with the exception of the grating, clearly not too dissimilar from the cooling tower described earlier and also attributed to Bedford. Steel, although considered initially for the construction, was eventually discounted principally on account of weight and speed of installation rather than as a result of the long-term non-corrosive nature of the chosen pultruded glass fibre – isophthalic polyester resin composite. Heavy-lift cranes with lengthy booms would have been essential with a steel version, a point firmly demonstrated by Bedford’s with a 1 m (40 inch) length of 0.45 m (18 inch) pultruded I-beam easily handled by two people, which in steel would otherwise have only been moved by mechanical means. The whole installation demanded just the use of fork-lift trucks, saving an estimated US$400 000 on heavy-duty cranage, a situation that adds strong emphasis to earlier comment that the manufactured cost of pultruded profile – and indeed composites generally – forms only a small part of the whole inservice costing equation.

6.9

Optical fibre tension/support member

For all their telecommunication advantages over the traditional copper versions, the friability of optical fibres together with their potential for surface and other damage which destroys or impairs transmission quality have demanded the development of a suitable support or, in other words, core member. This not only offers the required protection but acts in accepting all the tension, fixture and other installation or in-service loads that would otherwise be imposed on the optical fibre ‘bundle’. To satisfy other parameters, that tension member was required to be light weight, tough and flexible, available in small diameters and in virtually continuous length, totally resistant to any environment in which the optical fibre cable might be located and moreover be of the lowest possible cost at the highest possible surface quality (Fig. 6.13). Pultruded support members in diameters between 0.5 and 8 mm (0.02 and 0.3 inch) either in the form of solid rod or hollow tube and based on glass roving reinforcement in a MODAR 826HT acrylic resin matrix have answered this performance specification in an optimum manner and are

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6.13 Tension/support member for optical fibres (Courtesy, IPT, Top Cable, Austria)

Table 6.4.

Typical specification for tension member

Fibre type

E-glass

Fibre content

80% ± 2% w/w

Specific weight

2.1 g/cm3

Tensile strength

1400 N/mm2

Tensile modulus

50 000 N/mm2

Flexural strength

1850 N/mm2

Compressive strength

950 N/mm2

Elongation

2.2%

Water absorption (168 h @ 70 °C)

0.02%

Temperature stability

-50 to +120 °C

Data: IPT, Top Cable, Austria.

therefore now manufactured in increasing quantity by several large global concerns. Typical tension member properties are listed in Table 6.4.

6.10

Railways

As the development and growth of railway, mass-transit and ‘people-mover’ systems generally accelerate world-wide, so will their utilisation of pul-

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truded profiles. Three specific examples from among many have been chosen as suitable illustrations of that growing infrastructure market. Their order has been based solely on an alphabetical listing rather than any attempt to suggest their respective importance. However, in every case the success of the application has been linked among other advantages, to the combination of excellent electrical and environmental resistance properties.

‘METEOR’ guide bar METEOR is the fourteenth RATP line of the Paris underground system, connecting the southern part of the city with Gennevilliers. It has been designed for automatic train operation and continues the use of the pneumatic guide wheel and electrical power collection arrangements which over the years have proved highly successful and are now a famous part of the whole Paris metro and RATP system. Insulated portions of that guidance system are as illustrated in Fig. 6.14, provided by individual 18 m (60 ft) lengths of a pultruded profile manufactured by Doneco Celtite Profilex (DCP) of Villers-Saint-Paul, France. These insulating guide bar sections are mechanically fixed at 1.8 m (6 ft) centres, to the traditional guidebars/collection arrangement, and their 260 ¥ 90 mm2 (10 ¥ 3.5 inch) cross-section is detailed in Fig. 6.15. Satisfying the French fire and smoke resistance classification M1F1, the requisite profile has a

6.14 Pultruded insulated METEOR guide rail (Courtesy, DCO, France)

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260 mm

90 mm

6.15 Cross-section, METEOR guide rail pultrusion (Courtesy, DCP, France)

glass fibre content of 55% in an aluminium trihydrate-filled MODAR methacrylate resin matrix. At some 33 kg/m (22 lbs/ft), the profile is stated to be one of the heaviest currently manufactured in Europe.

Overhead catenary support A wide range of catenary support designs can be noted world-wide. Most are based on galvanised steel constructions which therefore demand the use of often complex insulation arrangements to support the high-voltage overhead electric power supply cable. However, the growing use of pultruded profile mast and tower assemblies for the industrial and domestic supply of electricity is now being duplicated by the railways for new constructions or over refurbished lines. While the extent to which the glass fibre, typically isophthalic polyesterbased profile alternative will be employed in the total construction, the additional advantages, which include light-weight, ease of erection and ability to withstand high wind speed loadings, are slowly being recognised and accepted as the preferred alternative to steel. A typical overhead catenary support arrangement is illustrated in Fig. 6.16.

Third-rail protective cover Although extensively employed world-wide as a means of collecting the necessary high and often DC voltage for both under- and above-ground railway systems, the third-rail arrangement for all its other advantages clearly presents a particular danger to both maintenance and all operating staff. With lines frequently passing domestic gardens and open farming land for considerable distances, it is surprising that accidental or farm-stock death is not much greater than it is. However, that risk has been recognised in the building of many new mass transit systems by the installation of third-rail covers whose careful design

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6.16 Overhead catenary support arrangement (Courtesy, Top Glass SpA, Italy)

protects those crossing the tracks but in a manner that does not impede in any way the electrical power collection. The ability to form strong, complex shapes in continuous length by pultrusion, to offer high strength, ease of shipment to and handling on-site of finished easily fixed profiles with high electrical and excellent environmental resistance, is now an accepted – and growing – market opportunity. Many suitable designs exist, that shown in Fig. 6.17 being very typical.

6.11

Rock-soil support applications

Pultruded tubes and solid bar in diameters typically <60 mm (1.6 inch) are, in addition to finding some application in for example hand-rail support systems, being increasingly employed as the basis of a variety of devices designed to improve the stability of both rock and soil faces before, during

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6.17 Pultruded third rail cover (Courtesy, European Pultrusion Technology Association)

and after tunnel excavation or other major earthwork. In other words, the permanent but also temporary installation of these devices sometimes in conjunction with concrete injection into those surfaces has the objective of preventing – or at worst limiting – the potential for collapse of any treated surface along existing weak planes or otherwise through surfaces that have been weakened by the tunnelling or excavation operation (Fig. 6.18). Compared with steel or even the thermoplastic versions which are suitable for some operations, pultruded pipe or rod exhibits a number of distinct advantages, one of which is a combination of mechanical and physical properties of benefit to their on-site installation. Ease of installation plays its obvious place in enhancing levels of safety and also the speed and costeffectiveness with which the whole work progresses. Pultruded pipe and rod also shatter more readily and with less danger than steel in any subsequent blasting procedure necessary to extend the treated tunnel surfaces or other excavation. In addition, however, to their long-term corrosion resistance, is the very high shear strength property which particularly assists for example in the pre-consolidation of the tunnel drive face or in the strengthening of the tunnel or other surface by in effect creating reinforcing ‘rings’ around that surface. Finally, because the elastic modulus is lower than that of steel, support devices based on pultrusions typically offer a much closer fit to the mechanical characteristics of the rocky mass.

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6.18 Installation of pultruded rock support devices (Courtesy, ATP srl, Italy)

To date more than 2000 km (1250 miles) of pultruded pipe and rod have for example been employed in Italy during tunnel works such as required by the new high-speed railway line between Rome and Florence. The supplier, ATP srl, lists a wide range of different pultruded tube or rod designs ranging from smooth surfaced tube, to those whose outer surface has been machined or roughened in some way to assist in the adhesion between device, any injected concrete and the excavated surface. Other threaded versions can after installation be fitted with external plates enabling the device to be tensioned in position.

6.12

Selection – custom profiles

There is a clear need in any review of pultrusion applications to reaffirm the importance of custom-moulded profiles, not just to that industry but to the customer at large. Like other comment within this chapter the number of custom mouldings now available world-wide that could be selected for illustration is legion and as a consequence there is a need to emphasise that Fig. 6.19 gives solely a small typical selection. Collectively they also encompass a dimensional range which can equally be considered as very indicative of current production. However, as also confirmed by Fig. 6.19 the vast majority of the custommoulded profiles currently pultruded could equally be classified under one,

Pultrusion applications – a world-wide review

a

d

b

e

c

f

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6.19 Selection of custom mouldings. (a) Channel profile 25 ¥ 95 ¥ 2.8 mm3 (10≤ ¥ 3.75≤ ¥ 0.11≤); (b) connection profile 130 ¥ 110 ¥ 4 mm3 (5≤ ¥ 4.3≤ ¥ 0.16≤); (c) corner profile 90 ¥ 52 ¥ 3 mm3 (3.5≤ ¥ 2≤ ¥ 0.12≤); (d) guide rail profile 100 ¥ 40 ¥ 10 mm3 (4≤ ¥ 1.6≤ ¥ 0.4≤), 5 mm (0.2≤) thickness (e) handrail profile 100 ¥ 81 ¥ 3 mm3 (4≤ ¥ 3.2≤ ¥ 0.11≤), 53 mm (21≤) diameter; (f) insulator profile 180 ¥ 25 mm2 (7≤ ¥ 1≤) (Courtesy, Nordic Supply Composites A/S, Norway)

or more, of the headings employed by this chapter. For example the channel profile is typically the cover to a cable tray or duct with the connection profile employed in vehicle construction, as is the corner profile. The handrail profile is obviously a special employed for that application, while the insulator profile has much the same use as the profile shown in Fig. 6.14. Finally, it is important to emphasise that like the vast majority of pultrusions generally and whether or not mineral filled, a glass fibre reinforced isophthalic polyester composition is and is likely to remain the most usual.

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6.13

Stagings and walkways

It is clear from much of the preceding market-application analysis that it is the structural properties of pultruded profiles that are particularly attractive to the designer and engineer. In other words pultruded profiles can be treated in exactly the same manner as, for example, steel sections, but gain advantage through their lightweight, high-strength and corrosion-resistant nature. Although they cannot be welded, the fixing and adhesive bonding techniques reviewed in the following chapter provide a very suitable alternative. As a consequence therefore pultrusions have found ready application in the construction of all forms of staging, stairways and walkways, uses that have clear links to fencing, railings and many of the other market areas considered by this chapter. They are, as has already been mentioned, obviously all inter-related. In addition every construction dimension from small to massive and whether required by the chemical processing or leisure industry to highlight just two market sectors, could be exemplified with Fig. 6.20 selected simply because it is so typical of the vast majority. Formed of standard off-the-shelf, self-coloured sections, the staging in Fig. 6.20 is supported on similar standard I-beams of suitable cross-section all demanding nothing more sophisticated in terms of the profile formulation than glass fibre reinforcement and a good-quality isophthalic polyester resin as the matrix. The only changes that may on occasion be required are the use of a vinyl ester matrix to further enhance the corrosion resistance or, as the profile dimensions increase commensurate with a higher structural loading, the possible use of a small quantity to carbon fibre laid down together with the glass in certain areas of the profile,3 typically in an I-beam, within the upper and lower flanges.

6.14

The ‘Eyecatcher’

A further example of the structural load-bearing acceptance for which pultruded profiles are now accepted is the residential/office building constructed for display during a 1999 Swiss building exhibition and dubbed the ‘Eyecatcher’. This five-story vision for the building industry (seen in part view in Fig. 6.21) employs simply flat, U- and I-profiles joined as required to form beams using a two-component UV-resistant epoxy adhesive which in turn were bolted together into sub-units to facilitate disassembly and later reconstruction when the structure will be employed as a permanent office building. Although in many ways therefore a trial or prototype construction, the Danish company Fiberline Composites has designed and constructed a building offering good thermal properties free of either cold or warm

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6.20 Typical pultruded staging and walkway (Courtesy; Bekaert Composites)

‘bridges’, which integrates the façade in a load-bearing construction of a building which is visible both internally and externally. In order to achieve an insulation value equivalent to a 300 mm (12 inch) wall, certain translucent panels of the façade form a sandwich construction filled with a superinsulating material trade named ‘Aerogelen’. Once again as confirmed by Table 6.5 the material combination of unsaturated polyester resin and glass fibre results in highly suitable mechanical properties for this type of structural application. To enhance their weatherability, the individual profiles employed a surfacing tissue and factors such as low weight, the ability to machine the profiles quickly and cleanly as required by the overall design ensured low assembly costs in comparison to traditional materials. Over the years the building and construction industry has made extensive use of composites approaching, if not for some countries exceeding, a

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6.21 The ‘Eyecatcher’ residential/office building (Courtesy, Fiberline Composites A/S, Denmark)

Table 6.5. Construction and associated data, ‘Eyecatcher’ structure Weight

10 tonnes (22 000 lbs) total

Height

14.5 m (48 ft)

Ground area

10 ¥ 12 m2 (33 ¥ 40 ft2)

Load-bearing capacity

3 kN/m2, with balcony at 4 kN/m2

Allowable deflection

L/200 (horizontal) and L/350 (vertical)

Courtesy: Fiberline Composites A/S, Denmark.

consumption level of 20% on the total annual finished product output. Among that massive tonnage now approaching a world-wide total of around 1 million tonnes (2.2 ¥ 109 lbs), have been many attempts to produce low-cost housing units, some of which have employed or have considered

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the use of pultruded profiles. There seems little doubt therefore that with the advent of the ‘Eyecatcher’ and for example the building described in Chapter 3 that this form of structural use for pultruded profiles will become common-place in the future.

6.15

Troll Phase One

The Norwegian Troll Phase One gas field project remains one of the largest European offshore developments that has made an extensive, successful use of composites (Fig. 6.22). Pultrusions manufactured in the UK by Fibreforce Limited were used in a totally typical manner for walkways, handrails and other structures required to bear heavy weight. However, incorporated within the design of an associated on-shore structure, there is a unique blast relief panel cladding system, constructed from a pultruded GRP profile manufactured by the same company. This system was required to have a fast opening response time of less than 25 milliseconds, to significantly reduce the peak overpressure generated within the affected area and in turn, therefore, reducing the need for additional structural reinforcement to ensure survival of the building. An aluminium construction had been considered, but after initial evaluation the two extrusions that would have been necessary required welding, a process judged too costly and time consuming. The use of composites provided, not unexpectedly, both an efficient manufacturing process and an optimum answer to these seven design and performance specification criteria: • • • • • • •

the lowest number of component parts; a long maintenance free in-service life; the lowest total installed costs; a minimum of base debris should the blast system be activated; flexible production in respect of a variable panel length; flame spread characteristics meeting Class 1, BS476 Part 1; and the minimum possible weight for fastest possible blast response time.

However, pultrusion was not the immediate composites fabrication choice. Hand-lay or contact-moulding had eventually to be rejected as unattractive for a production requirement of 30 000 m (98 400 ft), given the additional demands of minimum thickness and weight. Likewise another composites alternative, resin-transfer moulding (RTM), was not judged ideal to manufacture over the required volume a sufficiently reproducible, quality product at the necessary width of 448 mm (17.5 inches), particularly where a variable length of up to 7 m (23 ft) also applied. Using pultrusion, however, it was possible to provide a suitably structural profile, typically 3.5 mm (0.14 inch) thick and weighing 3.7 kg/m (2.5 lbs/ft), manufactured at some

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6.22 Blast relief cladding panel: Norwegian Troll Project, Phase One (Courtesy, Fibreforce Ltd)

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6.22 Continued

1500 m (4900 ft) per week and exhibiting the low flame-spread, low-smoke, low-toxicity fire hardness properties provided by an antimony trihydratefilled MODAR® methylmethacrylate–urethane matrix. However, the major advantage was the ability to incorporate in the profile design at a point of localised thickness reduction, a passive hinge of glass mat and KevlarTM reinforcement, where the latter is oriented perpendicular to the longitudinal axis of the cladding panel. When blast activated, the panel first rotates around and then shears along the deliberately weakened section, but is restrained from catastrophic failure by the presence of the KevlarTM fibres.

6.16

Vehicle body panels

The use of composites, moulded to shape by a variety of fabrication techniques, is now well established across the total car, bus and truck spectrum – and indeed including all forms of railway vehicle, cargo and ship application. In terms of the first three, those components range from decorative trim, through under-body and ancillary equipment mouldings, to structural elements and every form of external body panel. Overall it is one major composites success story, which is far from finished. However, although pultrusion delivers a product that, while perhaps complex in cross-section, is

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6.23 Pultruded bus panel

also continuous and straight and a design situation that must impose some obvious limitations to the use of the process within this whole market area (i.e. vehicle and related ‘body’ panels) where wrap-around, double curvature panels are more typical. Nevertheless two examples follow which demonstrate something of the available opportunity. Figure 6.23 illustrates a pultruded body/window mask panel from a bus following certain post-pultrusion treatment such as machining the window opening, edge finishing and painting. Obviously the use of pultrusion for profiles of this type is only cost-effective if the call-off quantity allows the considerable tooling cost to be suitably amortised. Therefore if the same basic panel can be employed for more than one location on the vehicle then those numbers are considerably improved. The other examples shown diagrammatically in Fig. 6.24 permit through their design as cladding for refrigerated trucks quicker amortisation because they (and like configurations) may have additional application in the lining of cold stores and clean rooms.

6.17

Water and sewage treatment plant

Traditionally two-thirds of the construction costs of water and sewage treatment plants lie in the civil engineering works which are static, inflexible and require continuous on-going maintenance. At a competitive cost, pultruded structures allow the minimum of site preparation, are fast to assemble,

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15mm (5.9”)

3mm (0.12”)

250mm (9.8”)

215mm (8.45”)

14 mm (0.55”)

320 mm (12.6”)

3mm (0.12”)

10 mm (0.39”)

6.24 Pultruded cladding panels for refrigerated truck construction

readily allow a variety of different size housings, enclosures, stagings, walkways and footbridges to be rapidly constructed which moreover are easy to adapt or resite at a later date. However, further illustration simply to repeat much of what has already been described seems superfluous, but this final list summarising the prime benefits of pultruded profiles to the consulting engineer involved with water and sewage treatment plant design is judged worth emphasising: • • • • •

The non-sparking property demanded by many industrial environments. A design deflection typically 1/200 of the span. A maximum span acceptance, typically 1700 for 5 kN/m of load. A low weight, allowing even large sections to be moved by hand. A fire performance which can readily meet Class I of BS476, Part 7, or better.

230 • • •

6.18

Pultrusion for engineers A thermal expansion similar to that of steel. Resistance to a wide range of environments and hazardous chemicals. Excellent electrical insulation.

Conclusion

Written by authorities within the industry, every chapter in this book rightly concludes on an upbeat note not just for composites, but particularly for the secure, promising and developing future of the pultrusion sector. These few examples from thousands provide adequate case-history support in confirmation, but one important factor is still lacking. Before pultruded profiles are purchased for whatever market and application, in increasing quantity, there must be better recognition and acceptance of their properties, benefits and advantages by the architect, consulting engineer, designer, specifier or purchase manger. That need for education has over the years failed until recently to be suitably addressed. The author of this chapter as editor of the whole book trusts that these pages will have the direct effect of therefore prompting interest not just in pultrusion, but in composites generally.

6.19

References

1. Christopher, W, & Carlson, P E, ‘Design considerations for a fiberglass, field erected, closed circuit cooling tower’ CTI Journal, 18(2) 52–61. 2. Andresen, F R, & Thorning, H, ‘Composite bridge based on standard profiles & elements’, Reinforced Plastics Asia ’97, Singapore, 1997. 3. Barefoot, G, Sitton, D, Smith, C, & Witcher, D, ‘Innovation of pultrusion structural shapes for infrastructure’, Paper 24E, International Composites Expo, 1997.