Advanced Carbon Fibre Application in Automotive: Present and Future Challenges

Luciano De Oto, Vehicle Design Engineering Director, McLaren Automotive Ltd

Carbon fibre composite materials are today widely used in the automotive sector for multiple purposes.

McLaren has used carbon ever since the MP4/1 Formula 1 race car in 1981. Since then, carbon fibre, with its ideal mix of strength, stiffness, and low weight, has been used in all forms of motorsport. It has also been used to varying degrees in a majority of supercars: McLaren Automotive, in line with its status as the pioneering supercar company, has not made a road car without it. To this day, it’s used in hoods, roofs, suspension components, strut bars, full chassis, body panels, and even trim panels.

In 2018, McLaren opened its McLaren Composites Technology Centre (MCTC) in the Sheffield region of Yorkshire in the North of the UK. MCTC is cementing its status as a world-leader in lightweight and composites materials technology.

The market for carbon fibre in automotive applications was estimated at more than 7,000 metric tons (MT) per year by Chris Red of Composites Forecasts and Consulting LLC (Mesa, Ariz., U.S.) at CW’s Carbon Fibre2017 conference, with more than 100 models currently specifying carbon fibre-reinforced plastic (CFRP) for OEM components. He projects this market will grow to almost 11,000 metric tonnes by 2025.

Today, China is now the largest car producing nation with more than 28 million vehicles produced in 2019, followed by the USA (around 11 million) and Japan with 9.7 million. China and Japan are now pushing composite development applications, especially in lower Automotive segments.

Just a few examples: Magna Exteriors has formed a joint venture with GAC Component Co. Ltd. (GACC, Guangzhou, China) to begin production of thermoplastic composite (TPC) liftgates. 

Jiangling Motors Corp. (JMC) is using composites materials for the pickup boxes of its new Yuhu 3 and Yuhu 5 pickup trucks. Kingfa (Guangzhou, China), thanks to a partnership with Brose Fahrzeugteile (Coburg, Germany) has developed a door module in carbon fibre organosheets and unidirectional tapes to cut weight by 35 percent (1 kilogram) for the Ford Focus versus a PP-LGF 30 door module carrier. Kangde Group (Hong Kong) and BAIC Motor formed a joint venture to build an Industry 4.0 smart factory in Changzhou to produce a carbon fibre bodies and other components scaling to 6 million parts/yr.

The rest of the world is trying to extend CFRP to lower segments but there are still concerns about costs for large scale production. This approach is limiting structure CFRP to supercars and using it only as decorative element for bigger volumes.

" Non-destructive methods are now able to guarantee reliable manufacturing processes and recycling techniques are also ensuring material sustainability for product life cycle "

There are numerous methods for fabricating composite components. Some methods have been borrowed (injection moulding from the plastic industry, for example), but many were developed to meet specific design or manufacturing challenges faced with carbon fibre. Selection of the proper method for a particular part, therefore, depends on the materials, the part design, volumes and end-use or application.

In the automotive world today the bulk of manufacturing technologies are still related to prepreg hand layup/compression moulding or RTM. Some supercar manufacturers - including McLaren – are pushing the boundaries with short fibre C-SMC applications to explore larger volumes production as well as to get the required freedom in geometries, that RTM and prepreg cannot always guarantee.

OEMs are therefore looking to out of autoclave technologies (OOA) for high-performance composite components. The high cost and limited size of autoclave systems has prompted many processors to call for OOA resins system. Ultra-lightweight C-SMC continues its push below 1.0 g/cc and several new C-SMC production lines have been installed over the past few years.

C-SMC is also used for structural applications, thanks to great mechanical properties that are equivalent or even better than many aluminium alloys. Its excellence in crash energy adsorbing is surprising automotive engineers and several applications have been already presented with that technology. Its potential is in front subframes developments, in tubs, rocker, lids, windscreen surrounds and many others.

The material can also be locally reinforced and co[1]moulded with patches of C-SMC made with carbon fiber 0-degree/90-degree non-crimped fabric. This C-SMC structural subframe must handle significant loads, supporting the engine and chassis components, including the steering gear and the lower control arms that hold the wheels.

A great benefit of C-SMC is also the possibility to integrate components, simplify geometries and further reduce weight versus traditional carbon fibre technologies. If compared with metals, C-SMC can achieve in some case 80 percent. parts reduction, replacing stamped steel parts with two compression moulded composite components and some co-moulded stainless-steel inserts, cutting weight by 30-40 percent.

Future manufacturing technologies will be more and more about out of autoclave processes, moving resins curing time from 10 to 2-3 minutes and eliminating the preforming step by offering cycle times of around 90 seconds and less-expensive equipment. Also, non-destructive methods are now able to guarantee reliable manufacturing processes and recycling techniques are also ensuring material sustainability for product life cycle. Additive manufacturing for composites is also possible today with several different methods, of which the Fused Deposition Modelling (FDM) is the most widely used. FDM builds parts of ABS, polycarbonate and other resins noted for toughness.

No less important is nanocomposites development that allows engineers to measure local stresses and strain in the laminate, detecting defects during product lifecycle and improving the mechanical properties of the material.