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Carbon fiber composite materials are today widely used in Automotive for multiple purposes. Automotive world has been progressively involved with carbon fiber for decades, ever since the McLaren MP4/1 Formula One race car was first to use a carbon fiber composite chassis in 1981. Since then, carbon fiber, with its perfect mix of strength, stiffness, and low weight, was used mainly in all forms of motorsport - as well as majority of supercar since developed, and marginally as well on road cars. To this day, it’s used in hoods, roofs, suspension components, strut bars, full chassis, body panels, and even decorative trim panels, that serve negligible practical benefits and still generates emotional responses among car passionate people.
The market for carbon fiber 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 Fiber 2017 conference, with more than 100 models currently specifying carbon fiber-reinforced plastic (CFRP) for OEM components. He projects this market will grow to almost 11,000 metric tonnes by 2025.In 2020, China was the largest car manufacturer with more that 28 million vehicles produced in 2019, followed by US (ca. 11 Million) and Japan with 9.7 million. China and Japan are now leading composite development application. Europe was leader till some years ago in motorsport and supersport cars application but didn’t dared to extend carbon application to a larger volumes. China and Japan are now challenging this market segment and pushing to implement advanced composites also on lower segments. Just a few examples: Magna Exteriors 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 fiber organosheets and unidirectional tapes, to cut weight 35% (1 kilogram) for the Ford Focus vs. 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 fiber bodies and other components scaling to 6 million parts/yr. Finally,Volvo has started production of its first model with structure and hat in carbon fiber, Polestar 1, in 2019 in the new Polestar Production Centre in Chengdu. Rest of the world is trying to extend CFRP to lower segments, but still with some concerns about costs for large scale production. This approach is unfortunately limiting structure CFRP to super sport cars and using it only as decorative element for bigger volumes.
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 fiber. Selection of the proper method for a particular part, therefore, depends on the materials, the part design, volumes and end-use or application.
In Automotive today the bulk of manufacturing technologies are still related to prepreg hand layup / compression moulding or RTM. Some high-end super sport car manufacturer, such as Lamborghini and McLaren are pushing the boundaries with short fiber 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 more and more 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.
“Future manufacturing technologies will be more and more about out of Autoclave processes, moving resins curing time from 5-10 minutes and eliminating preforming step by offering cycle times around 90 seconds and less-expensive equipment”
C-SMC is also used for structural applications, thanks to great mechanical properties, 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. Potential is in front subframes developments, in tubs, rocker, lids, windscreen surrounds and many others. Material can also be locally reinforced and co-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. Great benefit of C-SMC is also the possibility to integrate components, simplifying geometries and further reducing weight vs traditional carbon fiber technologies. If compared with metals, C-SMC can achieve in some case 80% parts reduction, replacing stamped steel parts with two compression moulded composite components and some comoulded stainless steel inserts, cutting weight by 30-40%.
Future manufacturing technologies will be more and more about out of Autoclave processes, moving resins curing time from 5-10 minutes and eliminating preforming step by offering cycle times around 90 seconds and less-expensive equipment. Also, non-destructive methods are today able to guarantee reliable manufacturing processes, 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 FDM (Fused Deposition Modelling (FDM) is the most widely used. FDM builds parts of ABS, polycarbonate and other resins noted for toughness.
Not less important is nanocomposites development that allows the Engineers measuring local stresses and strain in the laminate, detecting small defects during product lifecycle and improving mechanical properties of the material.