Home > Composites in daily life

Below, you will find a lot of examples of composites in your daily life. They are discussed in several subcategories:

• sports (cycling, skiing, tennis, canoeing, sailing,...)
• cars and motorcycles (hood, tyre, fenders, spoilers, brakes,...)
• house and garden (fenceboards, decking, bathroom fixtures,...)
• consumer goods (electronics, notebooks,...)
• health care (dentures, prostheses,...)
• travelling (aircraft interior, suitcases,...)
• public infrastructure (bridges, utility poles,...)

This overview is a personal compilation of a lot of news articles that appeared in recent years on the Netcomposites website.

Composite materials are very attractive for all kinds of sports activities. In many sports applications, weight reduction is the primary reason to move to composites.

One of the first sports disciplines where composites were applied, was the Formula One. Thanks to their high energy absorption for a very low weight, composites are widely used in all crash protection parts in Formula One race cars.
All Formula One race cars have a carbon fibre monocoque structure that protects the driver for all crashes. These structures are designed with advanced computer simulations, such as the monocoque for the Minardi Formula One race team, or the carbon fibre monocoque chassis of the Porsche RS Spyder race car.
Also in motor racing, composites are widely used. Aston Martin has returned in 2005 to the international motor racing scene with a carbon fibre panelled DBR9 race car.

Minardi Formula 1	Porsche RS Spyder racing car body	Aston Martin's carbon fibre panelled racing car

One of the most well-known composite applications in sports is the so-called "carbon bike". The frame consists of carbon fibre-reinforced epoxy which makes the frame very stiff and lightweight.
BMC, the Swiss high-tech bicycle brand, and Easton Sports have developed the "Pro Machine" for the Tour de France with a carbon fibre frame weighing less than 1 kg.
Carbon fibre bikes were also used by the British cycling team in the Athens olympics (Greece, 2004). The bikes were designed and built by the Advanced Composites Group (ACG).

BMC "Pro Machine" carbon/epoxy bicycle	BMC frame with carbon/epoxy pre-preg	Winning carbon fibre bike at the Athens Olympics 2004

Hexcel composites and Trek combined to produce a carbon fibre prototype frame which carried Lance Armstrong to his record-breaking seventh Tour de France victory. Trek supplied Armstrong with two new bikes: the SSLX climbing bike weighing only 6.8 kg (15 pounds), and the TTX time trial machine.
The German bicycle manufacturer Canyon Bicycles GmbH has developed a racing bike chassis of carbon fibre-reinforced polymer, together with the Institut fur Verbundwerkstoffe (IVW). Its high stiffness exceeded for the first time the magical limit of 100 of the stiffness to weight ratio, as the frame and fork have a weight of only 1260 grams.

Lance Armstrong's Trek Madone SSLX climbing bike	Lance Armstrong's Trek TTX time trial machine	World record racing bike developed by IVW

Other popular applications can be found in skis, surfboards and snowboards. They are typically made of high density polyurethane foam core with a thin composite skin.

Top ski design with foam cores	Surfboard with carbon nanotube reinforced epoxies	Surfboard fins with polyurethane foam core

Also in other recreational sports, composites can be found.
The performance of darts can be significantly improved by using carbon fibre for the shaft of the dart.
Xtreme Peaks Pty Ltd. designed the first mobile rock climbing wall made of composites. The semi-circular structure is 8 metres high, has five different routes of different difficulty and top rope attachment points.
Gurit supplied carbon fibre composite to manufacture two Olympic recurve bows. These bows smashed world records at the Archery Championships in Hungary (2006).

Dart made from carbon fibre-reinforced nylon	Mobile rock climbing wall from glass/polyester composite	Carbon fibre Olympic recurve bow

There are also a lot of experiments with Carbon NanoTubes (CNT) in composites for sports applications. These Carbon NanoTubes are very small carbon particles (size about one ten-thousandth of a millimeter) that are added to the polymer resin to increase its toughness and stiffness.
Easton Sports has teamed up with Zyves to introduce carbon nanotube technology to baseball bats and hockey sticks.
Carbon nanotubes are still very expensive to use, but engineers at the Fraunhofer Technology Development Group TEG in Stuttgart have devised a method that enables carbon nanotubes to be processed at low cost. Among the first products are the Vokl DNX tennis racquets. Carbon nanotubes are used to reinforce the frame at the points subjected to the highest stress.

Carbon fibre bat using Carbon NanoTube (CNT) technology	Hockey stick with Carbon NanoTube (CNT) technology	Carbon NanoTubes (CNT) in tennis racquet frame

Due to their excellent corrosion resistance and durability, composites are applied frequently for manufacturing hulls, decks, masts and booms of sailing yachts, catamarans and trimarans (three-hulled vessel).
One of the most famous carbon fibre trimarans is probably that of Dame Ellen MacArthur, who sailed around the globe, non-stop, single-handedly, in 71 days 14 hours 18 minutes and 33 seconds.
The Seawind 1160 catamaran won the award for Best Sailboat in 2005 and has benefited from the extensive use of composites.
Mirabella V is currently the largest single masted sailing yacht with a full composite hull, carbon fibre mast and booms.

Ellen MacArthur's carbon fibre trimaran	Seawind 1160 catamaran	Mirabella V largest composite sailing yacht

Probably the most renown sailing competition is the America's sailing cup. In that competition, all teams make extensive use of composites for hulls, decks, masts and booms.
This knowledge is then transferred to the recreational boating market. And even in most unexpected components, composites are integrated. Exit has introduced carbon fibre steering wheels for sailing yachts into the market. Due to their very low weight, they provide a much lower rotational inertia for a much more responsive helm.

America's sailing cup	Sailing yachts with composite masts and booms	Carbon fibre steering wheels for sailing yachts

Milliken introduced a new line of kayaks made with Tegris, a 100 % polypropylene thermoplastic composite. Polypropylene fibres are embedded in a lower melt polypropylene matrix. The material is fully recyclable and impact resistant.
Impact resistance is also needed in water sports, such as jetski, where the bottom composite panel is subject to slamming all the time.

100 % polypropylene kayak	Tegris fully recyclable kayak	Jet ski with chopped fibre Sheet Moulding Compound (SMC)

Cars and motorcycles

top

In automotive applications, composites are all around us. Just as in sports applications, weight reduction is pushing the designers to use more and more composites. The examples are numerous.

DaimlerChrysler has introduced the world's fastest open-top four-seater, the Mercedes CLK DTM AMG Cabriolet. Numerous body components are made from particularly strong and lightweight carbon fibre reinforced plastic, for example the bonnet, doors, front wings, flared rear wheel arches and aerofoil. Moreover the car body is made of carbon fibre composite.
In its prestige vehicles (Mercedes Benz CL and CLK ranges, Maybach 57 and 62 models) DaimlerChrysler uses composite decklids. They are fully permeable to radio signals, which enables GPS, GSM and AM antennae and amplifiers to be invisibly mounted within the decklid.
DaimlerChrysler has also been awarded for its innovative combination of polypropylene thermoplastic resin and banana plant fibre for the underfloor protection of its passenger cars. The product is resistant to stone strike, exposure to the elements and dampness. The company claims that the use of banana fibre can bring about primary energy savings of 60 percent or more, compared with glass fibre production.

Mercedes CLK cabriolet with lightweight carbon fibre body	Sheet Moulded Compound (SMC) composites for DaimlerChrysler decklids	Mercedes A class with underfloor protection in banana fibre composite

Also BMW goes for composites. The BMW M6 has an overall weight of only 1710 kg to generate 507 bhp (brake horsepower). The front wings, the roof and deck lid are made of composite.
The composite roof is 6 kg lighter than a conventional steel roof and it is bonded to the automobile body frame with a special Ashland adhesive.
In the BMW M3 model, the aluminium bumper beam has been replaced by a glass/polyamide bumper beam. A weight reduction from 7 kg to 3.1 kg was realized, and its crash performance was three to four times better than the metal beam.

BMW M6 with carbon fibre roof	Bonding of carbon fibre roof to BMW M3 CSL body frame	Glass/polyamide bumper beam for BMW M3

Composites are used in a lot of other sporty cars. The Peugeot 907 has been introduced with a complete carbon fibre bodyshell. Both the Lotus Europa S and the Lotus Elise 'Load Lugga' have composite body panels and a very advanced composite energy absorbing front crash structure.

Peugeot 907 with carbon fibre bodyshell	Lotus Europa S with composite body panels	Lotus Elise pickup with composite body

Maserati has launched a limited edition model of the carbon fibre GranSport.
The complex shaped fenders of the Chevrolet Corvette Z06 are made of composite, weighing just 3.5 pounds.
The 2006 Corvette's outer door panels (120 cm by 60 cm), roof bow and tonneau are made from fibreglass-reinforced composite.

Maserati Gransport MC Victory with carbon fibre body	Chevrolet Corvette Z06 with carbon fibre fenders	2006 Chevrolet Corvette with Sheet Moulded Compound (SMC) door panels

Apart from the car body, a lot of other car components are made of composites.
Goodyear has introduced the new Goodyear Eagle ResponsEdge Technology tyres. The outboard sidewall of the tyre is reinforced with a carbon fibre insert that provides stiffness for responsive handling and steering precision.
Kahn Laboratories have designed a 6 kg road wheel to reduce weight and radial inertia, thus improving handling, acceleration, braking times and overall performance. The wheel consists of a carbon fibre rim with magnesium centre.
The braking system of many modern cars is also equipped with fibre-reinforced ceramic brakes. The ceramic material's composite structure is made up firstly of silicon carbide. The high-strength carbon fibres are then embedded in the base material to absorb the stresses that occur in it. Audi introduced those brakes in the Audi A8, resulting in a weight saving of some 5 kg, or around 50 %, per wheel. The service life is up to 300,000 kilometres, four times greater than that expected of a steel disc. Plus, the degree of wear over the brake's service life is mere 0.5 millimetres.

Goodyear tyres with carbon fibre sidewalls	Ultra-light carbon fibre wheel (6 kg)	Carbon fibre-reinforced ceramic brakes for Audi A8

Composites are also present in the car's interior.
Fiberforge Harness Composite Technology has produced the Genus concept seat for the future automotive seating. The seat is made from continuous carbon fibre and nylon resin.
The newly designed dashboards for the VW Golf, VWEOS and Audi A5 Coupe are made of long-fibre-reinforced thermoplastics. On top of this thermoplastic composite, a fine polyurethane foam is applied, creating a soft-touch effect. Finally, a slush skin, usually of PVC, is applied on the foam surface to give the dashboard its special visual appeal.
The Maserati Quattroporte Sport GT has a carbon fibre interior.

Genus thermoplastic concept seat for future automotive seating	Long-fibre-reinforced thermoplastic dashboards for Audi and VolksWagen	Carbon interior for Maserati Quattroporte Sport GT

To solve the boot space problem, you can buy a fibreglass composite trailer, or a composite storage box.
Boot space is also a problem in the T-Rex three-wheeler superbike, a composite motorcycle with a glass fibre-reinforced body and carbon fibre windscreen and headrest.

"extra storage" fibreglass trailers for any passenger sedan	SDS Deckline storage box	T-Rex three-wheeler Superbike

Brammo Motorsports has launched the Enertia, said to be the world's first production battery powered plug-in electric motorcycle. The Enertia utilizes a carbon fibre chassis producing an ultra strong, light-weight vehicle platform of just 275 lbs.
Just like in cars, carbon fibre-reinforced ceramic brakes are gradually introduced into the motorcycle market. Starfire Systems has developed a new generation of ceramic composite brake rotor and pad combination.
BMW designed a futuristic composite helmet for its new cross-country BMW HP2 motorcycle.

Electric motorcycle with carbon fibre chassis	Starfire's ceramic composite brakes	BMW futuristic composite helmet for cross-country BMW HP2 motorcycle

In and around your house, the use of composites is still quite limited, although some nice applications are emerging.

Designers like to experiment with new materials, and composites are one of them. They are integrated in design furniture, such as the Leap office chair by Steelcase Inc., or the Orbit Chair by Bernhardt Design.
At the Cologne International Furniture Fair, probably the world's biggest sun blind, a 4 m high and 60 m long glass fibre construction, was on show.

Long-glass-fibre composite in Leap office chair	Composite orbit chair by Bernhardt Design	Composite sun blind

A large increase in composites can be found in the construction of maintenance-free composite doors. The doors have glass fibre facings, inner frames of a high density composite material and a core of rigid polyurethane foam that fills the voids completely and bonds to all surfaces.
An even more expanding market is that the composite decking market. The so-called wood-plastic composites and plastic lumber have the look and feel of wood, but have a much better durability and low maintenance requirements. Plastic lumber is used in fencing installations, while wood-plastic composites are also used for outdoor decking, window and door components, playground equipment and site and leisure furniture.
The adhesion of wood fibres with plastic is not easy to achieve, because wood and plastic are like oil and water, and do not mix well. Wood is hydrophilic - it absorbs water - and plastic is hydrophobic, repelling it. A "compatibilizer", typically a polymer that bridges the interface between the wood and plastic in these products, improves stress transfer and increases their strength and stiffness.
Teknor Color has introduced a color masterbatch for wood-plastic composites, that combines colour, UV absorber and biocide to control fungal growth. They can also incorporate pigments whose high level of infrared reflectance reduces heat buildup in deck components, which can cause polymer degradation.

Maintenance-free doors with glass fibre facings	Wood-plastic composites for composite decking	Composite decking with biocide-containing masterbatch

A few examples of wood-plastic composites and plastic lumber for privacy fence boards, fencing, colour composite railings, or fencing in equestrian facilities.

Lightweight composite privacy fence board	Wood-composite railings in different colours	Lifetime Lumber for use in equestrian facility

Another well-known application of composites is the manufacturing of swimming pools. Typically the pools are constructed with chopped fibreglass mat and polyester or vinylester resins. Telene has introduced fibre-reinforced DCPD resin, a new composite material, that allows for tiling on top of the composite structure, so that the water line can be decorated with ceramic tiles.
And if you want to heat the water of your swimming pool, you can install a solar collector on your roof. The French companies MIS and Saint-Gobain Vetrotex have developed a collector out of glass fibre composite. The collector is corrosion-proof, water-resistant, fully recyclable and much more efficient, as the fluid content is almost ten times greater than in a traditional collector.

Chopped fibreglass composite for high quality swimming pools	Composite swimming pools	Glass fibre thermoplastic sheets for solar collector

Finally, some nice innovations with composites are shown below.
Bayer MaterialScience has introduced the Formula One bathroom, where two modern polyurethane products are used to make the Formula One bathtub.
The same polyurethane foams were applied by a design student from the UK to add acoustic insulation to a toilet seat. The toilet seat reduces noise by 40 percent and is ideally suited for parents who may not flush toilets at night in case it might wake up the young children.
In a large development program "Windows of the future for houses of the past", the Danish window manufacturer Pro-Tec Vinduer A/S developed a fibre-reinforced composite window frame. The new windows ensure that home-owners will no longer have to contend with condensation, and heating bills can be reduced. The GRP material prevents thermal bridges and insulates very well. Moreover, the window cannot rot. It has a very long service life that is well-suited to the fluctuating weather conditions of Northern and Central European countries, and requires practically no maintenance. Paint does not peel because it adheres well to the GRP material, yet homeowners are still able to change colours if they like.

Formula 1 bathtub in short fibre composite	Toilet seating with integral skin polyurethane foams reduces noise by 40 %	Better insulated windows with glass fibre profiles

Although a lot of composites are used in consumer goods and electronics, it is hard to discover them, because they are usually integrated in the interior and the exterior housing is typically made of unreinforced plastics.

Yet a few nice examples are shown here. Acer was the first to present a carbon fibre cased Ferrari 4000 notebook. Later on, Sony also introduced the carbon fibre VAIO notebook.
Composite sandwich material is used in the Bowers & Wilkins (B&W) loudspeakers. The composite material fulfils both requirements of maximum sensitivity and damping, thanks to the combination of the stiff carbon fibres and low density Rohacell foam. The high mechanical performance of the material strongly reduces the deformations normally encountered in traditional cone materials under loads and so prevents sounds colouration. The loudspeakers are also used in the most prominent places, for instance the Abbey Road Studios in London, where among others the Beatles recorded many of their songs.

Acer's first carbon fibre notebook	Sony's carbon fibre VAIO notebook	Composite sandwich material for Bowers & Wilkins (B&W) loudspeakers

For many years now, composites are investigated for application in prosthetic devices, such as hips and other implants. Gradually they become a superior alternative to titanium alloys in the development of implantable load-bearing medical devices that require extra strength and biocompatibility.
Signus Medizintechnik and Icotec have developed the first cervical plate on the market that is made of carbon fibre-reinforced thermoplastic PEEK resin. The benefits are an excellent fatigue resistance and an artefact free imaging procedure (CT and MRI) for accurate and reliable post-operative monitoring. Problems with imaging often relate to difficulties interpreting radiographs taken through casts or fixation devices because the image quality is degraded as a result of absorption or scattering of X-rays. Carbon fibre-reinforced PEEK polymer is one of the most radiolucent of the composite materials. Also for prosthetic hips, carbon/PEEK composite is very popular, because it has a very high compression strength durability and its stiffness closely matches that of cortical bone, which is very important to prevent bone resorption.
The Canadian designer Sebastien Dubois has won the world's biggest design award for his concept "Mobility for Each One", a prosthetic foot which costs only 8 USD to produce. The prosthetic foot is made of glass fibre-reinforced composite and is intended to help civilians who are mutilated by landmines.

Carbon fibre-reinforced PEEK for cervical plate implant	Carbon fibre PEEK hip prosthesis	Glass fibre composite for 8 USD prothetic foot

Innovations with composites are also found in other health care applications.
Carbon fibre needles are being used during minimally invasive spine surgery, where magnetic resonance imaging is used to monitor the operation. One method of treating a slipped disk is to puncture the spinal disks, which involves injecting medicine into the injured area of the body with a thin needle. To be able to monitor the operation at all times and position the instruments accurately, the surgeon requires an image of the affected area, obtained using magnetic resonance imaging (MRI). The problem so far, however, was that conventional metal instruments interfere with the magnetic field of the MRI and distort the picture. A finished needle with one working channel has a diameter of 0.8 millimetres. Needles with three channels are a little thicker, measuring 1.2 millimetres. One channel, for instance,contains an endoscope that illuminates the tissue to be treated. Via the same route, the reflected light reaches a camera, and the operator sees a moving image on the monitor. The fibre in the second channel conducts laser light, which the surgeon can use to cut or weld tissue. The third channel serves to induct rinsing liquids or medication. In this way, several stages of treatment can be carried out and monitored simultaneously. The needle is suitable for spinal pain therapy, to inject contrast medium into joints for arthrography, and for puncturing cysts.
Vistasp Karbhari, a professor of structural engineering at UC San Diego, has assessed fibre-reinforced polymer composites for dental bridges. By changing the type and orientation of the reinforcing fibres, they can optimize these composite materials to match and improve performance of teeth, for greater durability, toughness and resistance to breakage.
The Scottish Ambulance Service has taken delivery of up to 180 Volkswagen LT46 coach-built ambulances with a glass fibre-reinforced body. The vehicles are built to conform to CEN (Certification of European Norm) standards; this dictates that all cabinetry and equipment within the vehicle remains intact in the event of a collision.

Carbon fibre needles for minimally invasive spine surgery	Fibre-reinforced composites for dental bridges	Coach-built emergency vehicle with glass fibre body

Most probably, the biggest race for composites is going on in the aerospace industry right now. Both Airbus and Boeing have decided to increase the share of composites in their new airplanes considerably.

The largest airplane ever built is the new superjumbo Airbus A380. It has a capacity of 555 passengers, an overall length of 72.7 m and a wingspan of 79.8 m. The share of composites is 20 %.
Composite parts are shipped from the United Kingdom, Spain and Germany to France, where the airplane is assembled in Toulouse.
The engine noise has been reduced with 3 dB compared to the Boeing 747, thanks to a single-piece composite engine inlet.

Superjumbo Airbus A380 with 20 % composites	A380 assembly in Toulouse (France)	Single-piece composite engine inlet for Airbus A380

And the next generation of aircraft will use even more composites. The Airbus A350 will have all-composite wings, and its competitor, the Boeing 787 Dreamliner, will have about 50 % composites. The fuselage was reduced by almost 20 % in weight by moving to composites, while it enables to have bigger windows, lower cabin altitude pressurization and higher cabin humidity.

Airbus A350 with all-composite wings	Boeing 787 Dreamliner with 50 % composites	Boeing Dreamliner composite fuselage section

Weight reduction is a key issue for every component in the aircraft. Fortron has replaced the seating elements from aluminium to a carbon fibre-reinforced thermoplastic composite, resulting in an overall weight saving of total 72 kg for every A380 with 555 seats.
ANA has developed a new economy class carbon fibre seat for use on domestic flights. The new design increases the passenger leg room by 5 cm, and the carbon fibre-reinforced plastic frame makes it 5 % lighter than the newest aluminium frame seats currently in use on ANA's fleet, meaning less fuel burn and fewer emissions.
Nordam has received approval from Boeing to supply the first composite window frame for a commercial airliner application. The new low density, high strength composite frame results in almost a 50 percent weight savings over a traditional aluminium frame. In addition, the frame offers superior damage tolerance.

Cutting weight with carbon fibre/PPS aircraft seating	Economy class carbon fibre aircraft seating	Composite window frames for Boeing 787 Dreamliner

Also train and bus interiors are made more and more in composites, due to weight savings. Important in these applications are the FST (Fire, Smoke and Toxicity) regulations, to prevent passengers from suffocating.
Diab has developed a fully recyclable thermoplastic core material for use in interior panelling, floors and exterior panels for trains, trams, buses and coaches.
China Railway Long Dragon wants to refurbish interior trim components used on its national railway system in advance of the 2008 Beijing Olympics. Together with GE Advanced Materials, they want to co-develop high-strength flame-retardant components for passenger train interiors.
Nova Bus, one of North America's leading manufacturers of urban and suburban buses, uses complete composite floors for its buses.

Sandwich composites for interior panelling in trains	Flame-retardant lightweight panels for passenger train interiors	Complete composite floors for Nova urban and suburban buses

Finally, in every-day commute traffic, you can maybe use a hybrid carbon/glass fibre folding bicycle, or show off with a composite suitcase or briefcase.

carbon/glass fibre folding bicycle	Self-reinforced all-polypropylene CURV composite for Samsonite suitcases	Briefcase in all-polypropylene CURV composite

In public infrastructure, the use of composites is growing more slowly. Main reasons are that weight reduction is a much less critical factor than in other industrial sectors, and in civil engineering, the cost of composites is very high compared to traditional building materials such as concrete and steel. However applications are emerging in construction of (foot)bridges, utility poles, repair of damaged concrete structures,...

Everywhere in Europe and America, a lot of bridges have been built in the 1960's-1970's, in the period of vast expansion of the highways. Most of these bridges are at the end of their lifetime or need urgent repair.
The first glass fibre-reinforced composite road bridge on the European continent was installed in the German town of Klipphausen near Dresden, Germany. The bridge is built entirely of glass fibre-reinforced profiles, and has the same load-carrying capacity as similar bridges in steel or concrete. The bridge is the result of years of research and development in the ASSET (Advanced Structural SystEms for Tomorrow's infrastructure) project which has been partially financed by the European Union.
Because the structural requirements are less demanding, footbridges are constructed more and more in composite. An advanced pedestrian footbridge spanning the Madrid-Barcelona high-speed rail link has won international acclaim in the form of the Footbridge Award 2005. As the bridge would cross a major rail link, minimising disruption to services was a key priority for the Spanish railway authorities. Accordingly, the bridge was assembled at the line side and then craned into place, resulting in a railway possession time of only three hours for the complete erection. Glass fibre composite does not conduct electricity, which is also very important as it means there is no magnetic interference with the electrified railway.
At the 2007 JEC-fair in Paris (the largest European exhibition on composite materials), the world's largest carbon composite bridge was shown. The carbon composite bridge is 24.5 meters long and 5 meters wide and weighs only 12 metric tonnes. This makes the bridge about 30 times lighter than a comparable concrete bridge.

First glass fibre bridge on European continent	Innovative glass fibre footbridge in Spain	World's largest carbon composite bridge

Gradually, bridges are also introduced on the highways, where load-carrying capacity is much larger. A fibre-reinforced polymer bridge is constructed over the M6 motorway in the UK, carrying 40 tonnes which is the standard for road bridges on the highway network. The bridge uses a glass fibre composite deck on steel girders, placed on reinforced concrete substructures.
Other applications of composites can be found in utility poles. Typically, glass fibre-reinforced polyester resin is used for the composite poles, which combine high stiffness and strength with low maintenance and easy installation due to very light weight.
Finally, composites are an attractive solution for repair of damaged concrete structures. Carbon fibre-reinforced strips are glued on the exterior surface of the structure and help taking up the loads of the structure.

Composite bridge on UK motorway	Composite utility poles	External strengthening of concrete structures with fibre-reinforced composite