Audi carbon fiber composite from pre-development to the production of Audi R8, A8 carbon fiber components throughout the stage, including: Audi R & D before facing the technical problems, choose their own research and development reasons, the design of load conditions, ultra-fast resin transfer molding Research and development of the road, after the success of technology suppliers to promote the use and future development of the road.
According to foreign media reports, Audi chose to design and develop its own carbon fiber composite structure, the company expects to achieve high-speed mass production in the future.Nowadays, advanced composite materials (advanced composites) in this market segment, car composite material or will become The darling of the industry's material suppliers and component manufacturers, the second most important target market in the market, is almost comparable to the aerospace industry.
Audi carbon fiber composite materials in the pre-development phase of the problems faced
However, steel and aluminum are still favored by the automotive industry. The growth of composite materials will take time and hard work from peers in the industry as it faces the following challenges: Complex structures are complex and because such composite materials are mixed with other materials This means that in order to achieve the required performance parameters, current design and simulation experiments also face many difficulties.
Unlike steel and aluminum, the complex has not yet been standardized production operations, which means that its higher production costs, longer production cycle.Although the major car prices are actively committed to the car lighter, trying to reduce the weight of vehicles.To this end, Audi Willing to seize this opportunity to focus on research and development of carbon fiber composite materials.
Now, the first question to be faced is: Audi should start from what?
The most common practice now is to start small batch applications, the gradual realization of high-volume production, which from the car's product development strategy can clearly feel that in the last seven years, Audi is the way to do this. The work started with the Modular Sports-Car System (MSS), which the company applied to the body design of the Audi R8 Coupe, Audi R8 Spyder, Audi R8 LMS (racing) and Lamborghini Huracan and many other models, the Lamborghini Huracan Is a two-seat sports car that uses a rear engine design layout.
Audi uses MSS as a tool to apply advanced carbon fiber composites to body-in-white (BIW) to reduce vehicle weight and improve vehicle performance. As the electrification of vehicles progresses, Audi More solidified this idea.David Roquette, research and development specialist for carbon fiber composite materials (CFRP) at Audi Lightweight Design Center, said that the first generation of Audi R8 models was made of aluminum but Audi decided to adopt the MSS project in the second generation R8 Of carbon fiber composite material.
So, the second question is: Which body parts will carbon fiber materials be applied to?
Roquette said Audi took three years to develop and assess the bodywork and eventually found the answer.He and colleagues took advantage of the company's in-house optimized software package for 23 load cases of the bodywork Then, they applied anisotropic stresses to the various body components, setting the values to the maximum, and then finding the most suitable part for the use of carbon fiber composite materials.
Roquette points out: 'However, stress is only one of these factors and the economy is also very important.What are the above two things that Audi has to make when it comes to carbon fiber materials? Does Audi have the technology needed to make carbon fiber composites? Cost and importance As the R & D work progresses, Audi's R & D personnel are gradually finding the automotive parts and components that meet these standards - with driveshaft tunnel and (car) rear wall ( rear wall. The rear wall functions to separate the passenger compartment from the rear engine compartment. According to Roquette, the rear walls of the 2016 R8 Spyder and Coupé models feature carbon fiber composite Significantly increased torsional stress and vehicle stiffness, as well as body weight reduction.
Load conditions of the design work
Felix Diebold, a colleague at Roquette, said that while the Audi Research Center focused on the 23 load conditions for the first time, the company was looking for new opportunities to increase the torsion stress of the white body with carbon fiber composite while reducing its weight Overall strength and passenger safety, Audi's design engineers combined a single-direction carbon fiber fabric reinforcements with a fast-cure epoxy resin system.
Diebold said Audi expects foam-cored sandwich construction for some of the R8 Spyder's composite components, specifically the B-pillar filler and the rear wall. Roquette said Audi is using a foam interlayer that is designed to Reduce the amount of carbon fiber in each structural member, B-pillar packing, consolidate part, and enhance its strength and rigidity.
When the roof of the Audi R8 Spyder collapsed, the model became a convertible, so strengthening the performance of the B-pillar became critical. The stability and rigidity of the undercarriage in non-convertible mode depend on The stiffness and strength of doors, roof frames, etc. In the convertible mode, the doors and other components are designed to ensure the required stability and rigidity.
Audi is hoping to use resin transfer molding (RTM) technology to inject epoxy resin into carbon fiber-coated foams, recalls Diebold, whose main challenge is finding an easy-to-handle inner core core material, and it should not be too heavy (100-150 kg / m3 density) or too light, otherwise the material will be crushed during RTM processing.
Audi finally finalized a new program that uses a foam based on polymethacrylimide (PMI), a relatively new product on the market. "Diebold said: 'The material is not crushed easily and is easy At the time, other core materials were also tried, but there was heat, cost or other restrictions that could not be finally applied to the material.
He added that molding can be used to machine foams into a variety of 3D shapes that enable the integration of raised parts, inserts and other metal parts without the need to run machines that process complex foam cores Processing and grinding.Moreover, according to Diebold, polymethacrylimide (PMI) materials have a homogenous cell structure that can withstand hydrostatic testing.
Ultra-fast resin transfer molding of the road to development
The last development challenge lies in the refinement of the RTM process, which Audi expects to bring together in a variety of materials using the new process, which is trivial compared to Audi's research and development goals. Ultimately Audi decided The work was handed over to a tier one supplier who was responsible for the relevant production work.
Roquette said high-pressure resin transfer molding (HP-RTM) has become the darling of automotive compounding manufacturers, although Audi has also considered whether to adopt the process, but the injection pressure up to 120-bar. If the pressure at the injection point is high , Will have an impact on the integrity of the foam core and Audi does not want to compromise on performance, so the company seeks new ways to reduce pressure on injection while ensuring that the production cycle will not be prolonged.
This may seem like an impossible task that was not solved until Audi contacted the R & D organization dedicated to the research and development of mold cavity pressure sensors, both of which were concerned with the fine-tune ) The injection molding pressure, compression force (compression force) and die gap were fine-tuned (fine-tuned) to further optimize the molding process.
Roquette said Audi is partnering with such research institutes and the tests show that if cavity pressure is a governing and primary variable during the molding process, the die clearance height and compressive force Perhaps an adjustable medium value that can be adjusted to ensure a fast production cycle as fast as possible and at least as fast as the high-pressure RTM process, Audi named the process as " Ultra-fast resin transfer molding (ultra-RTM).
For the sandwich structures of the Audi R8 Spyder, the injection pressure does not exceed 40 bar, the maximum molding gap can reach 0.6 mm, the maximum compressive force can reach 500 MT and the mold temperature can not exceed 123 ° C. With this new process, Injection molding time can be shortened to 15 seconds, while the overall production cycle time can be controlled within 5 minutes.This means that the parts can be processed using smaller, cheaper compressors, and lower energy consumption, not the core Material integrity poses a threat (not easily crushed).
New technology to the manufacturer's promotion and application of the road
Roquette said that when Audi first planned to manufacture complex parts for MSS, the company's first production strategy was to work with European automotive compounding processors, which may have the required capacity and expertise to be efficient And quickly design and manufacture the components Audi needs.However, Audi eventually decided to develop their own kind of complex materials and related processing technology.
Roquette said: 'As far as we know, if Audi really want to make technical breakthroughs in the field of complex materials, first of all, Audi's R & D personnel must be proficient in this area of technology, and secondly, be sure to use independent research and development.Audi has a large-scale R & D team, everyone is spending day after day working hard on the project.
When the results of the independent research and development of the Audi materials and processes have been achieved and passed on to the two largest European composite suppliers responsible for the actual production, the other parties also feel uncertain about the technologies and products that the cooperation considers, Roquette said : 'Because this is not the (mature) technology Audi acquired from the open market. Audi-selected suppliers have also produced such materials and have many years of experience in manufacturing technology. However, the independent research and development technology and suppliers The technologies used are very different and for the new technology it is a bit unacceptable for the suppliers.
He also said: 'To that end, Audi has provided technical demonstrations for suppliers about how their new technologies are being applied, and eventually Audi has convinced suppliers that the latter will be responsible for the production of such parts, for which suppliers But also take a lot of risk.As a supplier of car prices, it is really not easy to do this.
High cost constraints to create Audi continue to explore new technology
However, the R & D and application of this technology has not stopped with the 2016 R8 Spyder. In 2017, Audi introduced a four-seat luxury car, the Audi A8, which uses a carbon fiber composite back and upper rear shelf, Both components are made of carbon fiber composite materials, also have adopted the ultra-fast RTM process.
Roquette said: 'The larger the volume, the more the amount of work required.Carbon fiber finished parts cost is too high.Nowadays, the company will look at all aspects of the product, not only the price of carbon fiber, but also the RTM process In addition to the price of the resin, the price of the binder, the price of the entire material chain, and for that reason we must adopt a completely new concept. '