Increasingly versatile, sustainable and light, composites have found a way to move beyond niche markets and reach the automotive industry
Polymer composites make up a highly diversified category of materials. Like in the broadest universe of plastics, in this segment too the range of materials and solutions available is very vast, ranging from the more classical thermosets such as SMC (Sheet Moulding Compound) or BMC (Bulk Moulding Compound) to thermoplastics reinforced with filler and fibres, and to more specific segments such as elastomers and bio-composites, where both the matrix and the reinforcement can be made from renewable resources. In all cases, the goal is to combine the light weight of plastic with superior physical-mechanical properties, such as rigidity or resistance to impact, going on to cover structural or semi-structural applications replacing metals.
Compared to the past, today there tends to be a less engineering-oriented, more holistic approach to composites, looking, for example, to environmentally sustainable aspects, one the weak points of these materials, in addition to the shortfall in automation for processing. The new age of composites is founded on these two aspects, driven by the growing interest expressed by the automotive industry, which, with the electric and hybrid car in mind, the true challenge of this century, is looking for increasingly light, high performing and affordable materials.
Everyone is drawing on polymer materials with carbon fibre: car makers, OEMs, suppliers of parts and material manufacturers. And to ensure supply adequate for the demands of a sector used to thinking in large numbers (as opposed to the aerospace segment which works on small volumes), larger manufacturers are moving towards supply agreements or partnerships, in some cases internalizing technology and parts of the production process. Lamborghini, BMW and Daimler – to name only the biggest – have been working for some time to ensure strategic positioning throughout the pipeline, though with different objectives: small series for supercars, medium volumes for BMWs, moving towards the launch of two new ranges of electrical vehicles. Recently, the Fiat Group also announced its entrance in the world of composites, through its Ferrari and Alfa Romeo brands.
Italian-made goods are also being developed
Proof that something is happening in Italy came at the end of March, when Tecno Tessile Adler (TTA), a company of the Adler group based in Italy, inaugurated in Airola, in the province of Benevento, a new facility for the production of composite frames reinforced with carbon fibre, a component destined for the new coupé Alfa Romeo 4C. The new advanced materials plant, located in the former Benfil factory, has a production area of 38,000 square metres – in addition to 2,100 square metres for the offices -, part of which (3,300 square metres) destined for the production of carbon prepregs.
Once up and running, the facility will become the main Italian pole of composite materials for cars, counting on the collaboration of CNR (the Italian National Research Council) in developing production processes, partly experimented successfully in Italy in the aerospace sector (in Italia Alenia makes some large components for Boeing’s 787 Dreamliner). The new Adler site will also develop research, with the aim of developing advanced, high performance materials, in functional and aesthetic terms, and the relative processing technologies.[box title=”Investments in the United Kingdom for Italian cars” color=”#f8911b”]The Swiss group Gurit, one of the largest European manufacturers of composite materials and parts, announced last month that it has signed a 1.5 million euro agreement – the second in less than a year – with a “prestigious Italian carmaker” to supply carbon fibre parts. Deliveries will begin with some prototypes in the first quarter, and will start in earnest in the second half of the year. The growing demand in Europe for parts obtained using Sprint CBS technology is pushing Gurit to double its production capacity at its site on the Isle of Wight, Great Britain, a project that will be completed before this summer.
Sprint CBS is a family of composites reinforced with carbon fibres. This material is used as a component in the injection moulding of body parts with class A finishing. The parts obtained are made up of two layers of reinforcement in Sprint fibre, located above and below the resin core, in order to ensure maximum rigidity to the structure, comparable to steel or aluminium. They are finished externally with an in-mould film with aesthetic functions.[/box]
At the JEC show in Paris, the leading European trade fair dedicated to the composite industry, held in the French capital in mid-March, a partnership was announced between the Italians mould and machinery manufacturer Persico and the Future Fibres group from Spain: the goal of the Italian-Spanish alliance is to produce car parts in composite material.
The first project in the workshop is the car body, made entirely from carbon fibre, destined for the new RP-one racing car, designed by the British company RPx Automotive. The vehicle, approved for road traffic, will go into production in December, after more than five years of studies and tests on materials, weights and driving dynamics. The car body alone weighs 35 kg, while the entire structure, which integrates dashboard and door module, will not exceed 55 kg, enabling the vehicle to remain below the limit of half a ton (the overall weight will actually be 480 kg). A special feature of the projects is the visible car body, which emphasizes the high-tech content of the project with its raw appearance. Moreover, thanks to its low weight, the British super-car will not need powerful engine to reach a sports performance, to the extent that the future replacement of the internal combustion engine with an electrical engine has not been ruled out.
The engine goes bio-plastic, too
Lightness is not only a matter of weight, but also of environmental sustainability. This is above all true in the automotive industry, where the success of a new model is also based on its ability to arouse emotions and positive feelings in potential customers. As a result, the carmakers are shifting their focus on the environmental potential of materials in terms of recyclability and carbon footprint. More and more frequently, the choice falls on easily separable and recyclable materials, or materials obtained from biomass, which incorporate carbon dioxide (removed from the environment), thus improving the overall balance. It is difficult to imagine that a bio-based polymer can be used under a car’s hood, but – just like conventional plastics – bioplastics are diversified materials: those derived from castor oil, for example, are engineering polymers in all respects which, properly reinforced, can meet the strict requirements of the engine compartment.
A good example is represented by the cover of the turbocharged engine of the Mercedes A-Class. This component is moulded using the EcoPaXX Q-HGM24 compound from DSM, based on polyamide 410 obtained from 70% renewable resources and then reinforced with glass fibres and mineral fillers. The large (575 x 550 mm) component has to withstand without deforming both high temperatures (operating temperatures up to 200 °C with peaks of 235 °C) and the dynamic loads deriving from the engine block’s vibrations. The design requirements also include lightweight (it only weighs 1,320 grams) and good aesthetics, since the cover is clearly visible when the engine compartment is opened.
PFA and linen
The new developments in the bio-composites field include the combination of polyfurfuryl alcohol (PFA) with textiles made of natural fibres, such as linen, in order to obtain natural prepregs. These composites have been introduced in various reinforced versions by Composites Evolution in Paris as the result of four years’ research: besides linen, the company also delivers textiles made of oriented fibres reinforced with glass or carbon-fibres. The result – the company explains – is a lightweight composite material featuring excellent mechanical and flame-retardant properties as well as a low environmental impact.
PFA is a thermosetting bio-polymer, similar to a phenolic resin (including its flame-retardant properties), obtained from the hemicellulose that is taken from the waste produced during the processing of the sugar cane as well as of other biomasses. The version derived from PFA and the 100% bio-based Biotex linen can be obtained through the same processes used for conventional glass-fibre reinforced composites: under vacuum conditions, by using an autoclave or moulding techniques.
Interesting developments in this field were unveiled at JEC by NetComposites, too. The company is involved in the Eco-LFT research project, aiming at developing new processes for producing long fibre reinforced thermoplastics (LFT) directly starting from mixed natural fibres; the pellets obtained in this way are then fed to the injection moulding press. According to NetComposites, committed to optimizing the addition process, the automotive industry represents the most interesting application field for these materials, which offer a sustainable alternative to the glass fibre reinforced thermoplastics used in front-end modules, doors and tailgates.
Another recent development is represented by Biotex flax, a 100% bio-based prepreg. The polymer matrix is – here too – based on polyfurfuryl alcohol (PFA) reinforced with linen fibres: a semi-structural, flame-retardant material is thus obtained which could offer an effective alternative to glass-fibre filled phenolic resins used in the transportation and building industries.
Thermoplastics or thermosets?
A major trend emerging in the automotive industry is the gradual shift of focus from thermoset matrixes to thermoplastic resins. There are many reasons for this: thermoplastic composites are lighter, easier to recycle, are more handsome and require fewer finishing operations, and offer considerable opportunities in the automated mass production of moulded parts, these being all critical factors in the automotive industry as well as, although less evident, in other industrial segments.
This trend drove, for example, the decision of Iveco to switch from the sheet moulding compounds (SMC) to a PBT/PET blend for the bumpers for the third generation of Eurocargo midsize trucks. The grade selected for this application is Lanxess’ Pocan TP 525-001, reinforced with glass fibres and modified with elastomers in order to ensure high mechanical strength and, at the same time, to absorb the minor impacts typically experienced in urban traffic without being damaged. The component (measuring 2200 x 700 x 300 mm) is produced by Martinplast, a company based in San Martino Alfieri, near Asti, Italy. Lanxess emphasises several benefits deriving from the replacement of SMCs with thermoplastic composites, including the elimination of post-moulding finishing operations, light weight (the part is 20% lighter), the reduction of wastes, shorter cycle times and better aesthetic properties. It is worth noting that the end product does not require any additional finishing operation, thus eliminating the primer application and polishing steps. The material can however be painted, as required by some special Eurocargo versions. On the other hand, injection moulding requires more expensive moulds, and this extra cost can be only justified when production batches are sufficiently large, such as in this case.
At JEC this year, Fokker Aerostructures, AgustaWestland (Finmeccanica), TenCate Advanced Composites and Ticona won awards for the industrial development of the first horizontal stabilizer of exhaust tubes in thermoplastic composite (prepreg in polyphenylsulfone PPS by Fortron) reinforced with carbon fibre, mounted on AgustaWestland AW169 helicopters. The three metre long piece weighs 15% less than before, and is made of thermoset composite.
None of the two…
“Class” distinctions can be overcome however. That is what Altuglas is trying to do at present. The company belongs to the Arkema group and received a JEC Award in Paris in the Thermoplastics category for the development of the new Altuglas Composite methacrylic resin. As the French company explains, this is a thermoplastic – and as a result thermoformable, weldable and recyclable – material, but it can be processed by using the same methods, systems and moulds employed for thermoset resins.
Developed together with the Pole de Plasturgie de l’Est (PPE), in cooperation with MVC (Brazil), Chomarat (France) and 3B-fibreglass (Belgium), this new composite can incorporate continuous glass, carbon or natural fibres. It can be converted using the conventional resin infusion moulding or resin transfer moulding (RTM) processes, thus obtaining parts whose properties are very similar to traditional thermoset composites, such as unsaturated polyesters, vinyl esters or epoxy resins, in terms of mechanical strength, rigidity and curing time. The acrylic nature of Altuglas Composite also enables composite and metal-composite components to be assembled by means of acrylic adhesives or welding processes.
Altuglas and MVC have developed a range of formulations destined for the production of semi-structural aesthetic parts for the body of industrial vehicles, buses and agricultural machines. The two partners, with the support of the PPE, have already manufactured a first large demo product – the hood of an electric city-car – by using the RTM-light process at ambient temperature.
PVC is also reinforced
SolVin presented at JEC Europe Composites Show in Paris two new families of vinyl matrix composite materials. The first, FibroVin, developed in collaboration with the French Fibroline, impregnates the PVC with long glass fibre, to obtain a rigid impact resistant and flame retardant material. The second family of composites, christened Autoflax, is obtained by adding continuous linen fibres to the vinyl resins SolVin and NanoVin. The result is a lightweight material with thermal and sound insulation properties.