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Interview: Christophe Aufrere, Chief Technical Officer, Faurecia

Freddie Holmes speaks to Faurecia’s CTO about the Tier 1 supplier’s “relentless effort” to help OEMs make vehicles lighter, safer and more efficient

With vehicle emissions and fuel economy under increasing scrutiny, opportunities to lessen the strain on vehicle powertrains are being welcomed by automotive OEMs. Lightweighting has become an obvious first step for OEMs, and suppliers need to meet this demand with new solutions.

Faurecia’s core businesses in automotive seating, interiors, emissions control technologies and exteriors contribute up to 250-300kg (550-660lbs) in a C-segment passenger car, according to the supplier’s Chief Technical Officer, Christophe Aufrere. What’s more, every 10kg saving in weight leads to a 1g/km reduction in the car’s CO2 emissions. As such, “weight is a constant preoccupation,” he says.

In this exclusive interview, Aufrere discusses Faurecia’s long-standing approach to lightweighting, and outlines the company’s use of new materials across its portfolio for further savings.

In Faurecia’s view, what are the most obvious ways of reducing vehicle body weight?

We began by optimising existing materials through the use of high-tensile strength steel grades for our seat structures, mechanisms and exhaust systems tubes, thus reducing thickness. We then developed new welding solutions compatible with this thickness reduction, such as laser welding for seat structures and induction brazing for exhaust lines.

In our exteriors business, which makes vehicle body parts such as bumpers, fenders and liftgates, we have also reduced material thickness; less material means less weight, with no impact on perceived quality for the end-user. We have also been experiencing the advantages of composite materials, which can bring weight-loss gains of up to 50% versus steel in a variety of applications in our four business groups.

What can you say about lightweighting for vehicle interiors?

In our interiors and exteriors businesses, we have worked on improving weight-to-performance ratios. We have been pioneering the use of bio-materials for interiors over the last 25 years, such as wood chips, flax, hemp and other bio-sourced and renewable materials. These materials have the advantage of being both up to 25% lighter than traditional fillers and fully recyclable.

Faurecia CO2 regulations chart

Lightweighting can be expensive. How can Faurecia’s solutions help OEMs balance the need for lightweighting with the need to cut cost?

In the automotive industry, cost is of course of prime importance and we have to work closely with the OEMs to find the right balance between the advantages of lightweighting and the cost aspects.

Lighter is not necessarily more expensive. We are relentlessly working in our R&D labs on delivering solutions at no added cost over the vehicle lifetime. For example, working solely on steel improvements, we have been able to offer more standardised and lighter seat structures as well as complete exhaust lines at no extra cost, even sometimes at a better cost thanks to first class quality, manufacturing processes and higher volumes. Stainless steel exhaust lines are now designed for the lifetime of the vehicle and no longer need replacing. Faurecia seats offer the highest levels of safety for front and rear passengers, although their weight has dropped by more than 25% over the last decade.

You say that lightweighting need not be more expensive, but it does come at a cost…

Yes, and it is a choice which OEMs are ready to make, in particular when the costs and associated weight benefits are evaluated over the lifetime of a vehicle or vehicle platform. Gains in manufacturing costs also stem from process optimisation and the generalisation of vehicle platforms, spreading the extra cost over higher production volumes. For example, if you develop a seating platform for one vehicle for one brand, it’s a different equation when you develop a global seating platform for up to ten vehicles for several brands, as has been the case for Faurecia with the Renault-Nissan brands.

The same approach applies to exhaust systems, which are essentially made of stainless steel. On the other hand, as the fuel consumption and CO2 emissions have to drop, lightweighting is a competitive solution versus others. For example, why should an OEM develop a hybrid vehicle if it can instead reduce the weight of a vehicle by 200kg (485lbs) for the same performance? An 800kg vehicle consumes 3 litres of fuel per 100km, resulting in CO2 emissions of around 75g/km.

What are the lightweighting options that Faurecia can offer the OEMs?

When looking at ways to reduce the weight of parts, we mainly look at steel and plastics. For steel, progress can still be made but weight gains will be minimal, as some limits – thickness for example – have been reached. We are exploring alternatives such as aluminium, magnesium, hybrids and composites for seating, whereas for exhaust systems, stainless steel remains the preference. However, some plastic or composite parts could find applications on muffler parts, for example.

A promising area could be in hybrid concepts, which encompass high-strength steel with composite reinforcements, such as our seat concept for the Renault Eolab prototype in 2014. And in the area of hybrid cross-car beams, we’ve seen full carbon fibre concepts. Even replacing an entire vehicle floor, traditionally made of steel, with a glass fibre composite could be a viable alternative, with 35% weight reduction expected.

For plastics, the integration of natural fibres for injection is a trend we want to follow for interior parts where we can reduce weight by 25%, and continuous fibres for load floors with a significant saving of around 40%. Replacing traditional plastic or structural steel parts with composites is an area Faurecia has placed at the forefront of its research for lighter materials. Even in this area, improvements are expected in the design, material, processes and simulation areas.

Do you see any potential for magnesium in automotive applications?

Magnesium, as an alternative to steel, comes first before aluminium in terms of weight savings, with parts weighing around 30-35% of equivalent parts in steel. However, its applications are currently quite limited. Faurecia has been investigating all kinds of magnesium technologies, such as high-pressure die casting and thixomoulding. Prototypes of injection-moulded magnesium seat frames have recently been made and are currently at pre-validation stages. This technology, which needs to integrate functions to lower the price differential versus steel, is particularly hard to master for parts exposed to a crash. We are cooperating in this field with FAW Foundry, a leading Chinese foundry company specialising in magnesium, since China is the world’s primary source of magnesium ore.

For exteriors, Faurecia is not currently working on magnesium, although some industry players have shown applications of magnesium sheets for body parts such as roofs. The cost of magnesium sheets is the main constraint, due to the limited number of suppliers and the complex assembly process. In the automotive interiors field, we have not been investigating the use of this material.

Faurecia lightweight materials chart

What are the challenges of working with magnesium in these cases? Are weight savings worth the challenging manufacturing conditions?

For magnesium, the constraints are mainly cost versus steel and the fact that it is quite friable, at least in its injection-moulded version. There could also be specific constraints due to crash resistance and durability. In the injection-moulded field, some advantages include the integration of functions which allow for different thicknesses. Compared to steel, magnesium sheeting is more difficult to stamp and the assembly processes are more complex. Apart from weight loss and more design freedom for moulded parts, there are no direct industrial gains.

Carbon fibre has an attractive strength-to-weight ratio, but cost is still a hindrance. Can the material be brought into mass-production in future?

The mechanical and lightweight properties of carbon fibre for automotive applications need not be restated, with a potential of 50% mass reduction. The main roadblock is indeed its cost.

In addition to working on the material cost itself, Faurecia is actively working on carbon composite product, process conception and simulation. Faurecia has pioneered the launch of a multi-year project in France, dubbed FORCE, aimed at reducing the cost of carbon fibre from approximately €14-15 (US$15.6-16.7) per kilogram down to €7-8. At that cost, for automotive applications it would enable the mass production of carbon fibre parts while also respecting the industry cycle times of one part per minute. The main objective of the project is to work on new precursors, simplify the carbonisation process, validate the mechanical properties, and develop the necessary simulations to reach the cost target. Such affordable carbon fibre is expected to be available post 2020.

What is Faurecia’s stance on carbon fibre use across its core businesses?

All four of Faurecia’s business groups potentially have plans for carbon fibre utilisation. The most obvious applications are for structural and semi-structural body-in-white parts such as vehicle floors and B and C pillars, as well as exterior parts like liftgates, hatch doors, roofs, hoods, trunk structures and doors.

The weight savings that could be achieved by replacing such large steel parts with their carbon composite equivalents would save tens of precious kilograms, which would have a lasting impact on weight and CO2 emissions. Other applications could include seat structures, and within interiors its use is mainly foreseen for cross-car beams. Equally, we are investigating both thermoset and thermoplastic composites, while using continuous fibres for structural parts, cut fibres for semi-structural parts and recycled thermoplastic composites which could be used as granulates for injection moulding.

This article is part of an exclusive Automotive World report on lightweighting. Follow this link to download a copy of Special report: Vehicle lightweighting

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