both carbon and glass fibres, and 3.4 kg (39%) by using only glass fibres in the new front beam structure compared to the steel counterpart. Its more affordable cost and fast production process also ensure that the new component can be applied to high-volume production.

The new structure was also subjected to extensive validation and testing, and is expected to fulfil the same perfor-mance criteria as the steel counterpart. The modular generic design can also be readily adapted to other Hyundai model platforms.

Establishing the project’s concept and finding appropriate partners took nine months, with development then running

from September 2012 to May 2015 (30 months), an extremely short time span for such an innovative and complex development. The project partners were Plastic Omnium (France) and its project manager Stéphane Ginja, who suppor-ted the Hyundai team in the project management, CAD concept and CAE

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Hyundai’s breakthrough front bumper crash beam

The innovative front bumper crash beam structure developed by the Hyundai Motor Europe Technical Centre features the world’s first Curved Reactive Thermoplastic Pultrusion (CRTP) process and incorporates four innovations. The structure won the JEC Innova-tion Award Europe 2015 for Automotive Safety.

Stephane Ringenbach,

Section ManageR, coMpoSite & LightS

DR. JuLien Richeton,

ManageR, coMpoSite MateRiaLS

DR. JeRoMe couLton,

ManageR, coMpoSite cae

hyunDai MotoR euRope technicaL centeR gMbh

By

The Hyundai Motor Europe Techni-cal Centre (HMETC) has broken new ground, developing a new front

bumper crash beam that consists of an inno-vative composite insert overmoulded with plastic resin. The insert, obtained using the world’s first Curved Reactive Thermoplas-tic Pultrusion process (CRTP), is com-posed of unidirectional glass fibre rovings, glass textiles and the optional use of carbon fibres. A new integrated towing insert was also developed as part of the pioneering project.The project’s main challenge was the development of four innovations: - a pultrusion process using liquid in- mould reactive polymerization;- new in-line curving equipment for the thermoplastic pultrusion;- mixing continuous unidirectional glass, carbon fibres and textile reinforcements;- development of the adhesion between the composite insert and the overmoul- ding resin.When combined, these advances allow a 3.6 kg (43%) weight reduction by using

CRTP

Fig. 1: Composite Beam in front of HMETC

Fig. 2: Hyundai Motor Europe Technical Center Ruesselsheim, Germany

fibres are impregnated with a liquid poly-mer precursor (the monomer) and intro-duced into a pultrusion die. The monomer is then polymerized through heat into a polymer resin during the forming process so that the fibres and plastics are bonded within just one process – “liquid in-mould reactive polymerization”. This not only cuts weight dramatically, but also reduces complexity considerably. Consequently, the new structure comprises only three major parts, produced and assembled in two continuous production steps compa-red to 26 different parts and the various assembly steps of its steel counterpart.

Curved Reactive Thermoplastic Pultrusion (CRTP): a world firstAnother feature of the reactive thermo-plastic pultrusion process was the need to develop special equipment to pull the composite insert into a 2-metre radius and cut it to the right length, matching the existing part geometry of the steel coun-terpart. This breakthrough in composite production was developed exclusively for Hyundai and meant that, for the first time, a curved shape could be produced in just one rapid production step, making it not just superior to conventional composite production processes, but much faster and less complex than bending the current high-strength steel structure. The insert is then placed into a conventional moulding tool and a plastic resin is injected onto the pultruded insert to finalize the front bum-per beam. This combination of innovative materials and processes with a highly cost-efficient standard production technology, like conventional injection moulding, makes the process very competitive and feasible for mass production.

simulation; CQFD Composites (France), who provided insights into the reactive pultrusion process and built the pultru-sion equipment; and Arkema (France), the specialist partner for field chemistry and material testing.

Start of the projectBack in November 2011, the Composite team within the Engineering Design Depart-ment at HMETC in Rüsselsheim (Germa-ny) was asked to look at the front bumper beam structure of the current Hyundai i30 model as part of an overall weight-saving programme on that car, which might also be applied to other Hyundai platforms.This experienced team is asked to tackle many improvement projects, but this quickly became one of the most challenging because the front bumper beam structure not only has an obvious role in occupant and pedestrian safety, but its shape and weight also affect how the car handles. As the front bumper is the lowest and foremost part of the car, any extra weight is particu-larly unwelcome, so here was a clear task for the Hyundai team: to cut weight without compromising safety, raising production costs dramatically, or compromising mass production feasibility.

Don’t take the easy wayBut while it was easy to see the gains from saving weight in the existing i30 front bumper and how these might be applied across other Hyundai models, the team also knew that the i30 front beam structure was already the best in terms of performance and weight within the Hyundai line-up. Clearly, the team had to apply the compa-ny’s “New Thinking. New Possibilities”

philosophy rather than take an easy way out; a real breakthrough was needed to deliver the required performance, cost and production benefits.

Over nine months, Hyundai engineers based at HMETC thoroughly investigated the latest composite materials and manu-facturing methods based on numerous discussions with automotive and raw material suppliers, in addition to pro-minent universities. Despite their efforts, the team found nothing in the existing “toolbox” that could match Hyundai’s high expectations in terms of weight, perfor-mance and cost, and the team had to come up with its own “breakthrough” concept. For example, using only carbon fibres could have reduced the weight signifi-cantly, but the material costs would not fit with mass production. On the other hand, with the existing i30 front bumper beam structure already featuring a weight of 8.7 kg and entirely composed of high-strength and ultra-high-strength steels, it was obvious that a design optimization of the current steel part could not deliver massive weight improvements. In any case, with 26 different parts, 24 laser welding lines and 85 arc welding lines – a total length of 2.1 metres – the production and assembly process for the current product was quite complex.

A breakthrough for automotive composite partsWith conventional solutions discounted, Hyundai chemists and engineers had to think “outside the box”’ to meet the project targets. Creating an advanced composite material was soon considered due to its relatively low cost compared to its strength and performance, and the scope for innova-tion in this field was promising too.

After investigating different materials and processes, reactive thermoplastic pultru-sion supplied the initial breakthrough. This low-viscosity process, developed by the partner company CQFD Composites (France), is a continuous manufactu-ring method for composite parts with a constant cross section. Glass or carbon

CRTP

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Fig. 3: Composite Beam

Fig. 4: I30 Steel Front bumper Beam exploded view

the new front bumper crash beam, but also simulations for this new structure. Developing these alone took almost a year because the final composite material – the mixture of carbon and glass fibres, and the resin – simply had not been seen in the automotive industry before, so no simula-tion data was available. This meant setting up extensive mechanical tests under various conditions to create data, finally delivering accurate simulation results ready for mass production application. But if this aspect had given the develop-ment team a temporary headache, it was more than relieved by realization that the new materials and processes could cut short production time.

No compromise on design, safety and performanceThe resulting front bumper crash beam, based on the Hyundai i30 front structure, could now be fitted to the car without any adaptation to the car structure. Even the foam elements behind the front bumper fascia could be re-used with the new parts. This production compatibility is matched by the safety of the new part: the front bumper crash beam fulfils the same speci-fications as the current steel structure and passed all relevant crash tests, such as the low-speed insurance test, the pedestrian protection test and even the EuroNCAP 50 and 64 km/h crash tests. Furthermore, the new construction also includes a towing hook that is fully compliant with all internal Hyundai load tests as well. n

More information: www.hmetc.com

While finalizing this second production step, Hyundai experts and the partner companies also combined forces effecti-vely to overcome another challenge when the adhesion between the composite insert and the overmoulding resin proved too weak. They soon adapted the over-moulding resin to deliver the necessary stability and strength.

Getting the right mixtureWhile working with different fibres and composites, a number of variables were difficult to calculate, e.g. when combining unidirectional glass and carbon fibre rovings within the insert. The materials do not have the same coefficient of thermal elongation so, when the final insert cools down, the whole part can twist and de-form. Therefore, it was crucial to place the carbon fibre exactly in the right places and get the mixture of all materials correct to avoid any distortion at the end. Hyundai developed two final versions of the new insert with different combinations of glass and carbon fibre rovings to showcase the potential of the new technology.

Significant weight reductionThe main benefit of the newly developed process and the resulting front bumper beam structure, composed of both glass and carbon fibres, is a 43% (3.6 kg) weight reduction versus the conven-tional steel structure. Furthermore, the additional costs compared to the steel

structure are minimal and, last but not least, the new structure is fully recyclable: the thermoplastic materials used for the composite insert and the overmoulding can be melted down and reused, which is not possible with most other solutions on the market.

Building the first prototypeIn order to deliver a prototype, various meetings of the Hyundai team and project partners were held and countless calculations made of how the injection mould and the pultrusion die should be. With such new materials and production processes, there was no experience in how dimensions might change when the composite cooled down. Despite this, the composite insert fitted straight away when added to the injection mould, so well that no tooling changes were made after this prototype stage: a pleasant surprise, but proof of the huge effort and professionalism of the Hyundai team and its highly committed partners. As a result, the only follow-up work was some process optimization of the overmoulding parameters; the dimensions of the pultru-sion insert were not modified further.

Mass production feasibilityPart of the mass production challenge was not just creating the parts and production process, but the tools to produce the new structure. So Hyundai and Plastic Omnium not only created CAD data for

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About HMETCAbout HMETCAbout the Hyundai Motor Europe Technical CentreThe Hyundai Motor Europe Technical Centre in Rüsselsheim (Germany) is a young, dynamic company with its roots in South Korea. Established in 2003, the organization has grown constantly since then; its 250 employees are responsible for developing and designing future gen-erations of vehicles and technologies for the whole European market and beyond.