Audi, Hexcel and Secar Technologie have teamed up to develop a composite engine mount for the Audi R8, which is overmolded with HexMC-i 2000 carbon/epoxy molding compound to produce Secar-drawn carbon fiber sections and Hexcel highly structured Mixed structure.
Based on previous successful cooperation, Hexcel's automotive business unit approached Audi's composites development team in early 2016 with the aim of aligning the HexMC-i with the production-prepared manufacturing process. This move not only allows Audi to evaluate The current market for carbon fiber sheet composites has also selected the most suitable parts for the R8 engine.
The V10 engine bracket in the Audi R8 is supported by a cross-shaped component, which not only improves the torsional stiffness of the engine, but also enhances the driving dynamics of the car. The goal of the project is to produce a composite version of existing aluminum components that significantly increase the lightweight rating of the car and enhance the visual appearance of the part by providing a more organic molded shape. The technology is patented by Audi. .
Rapid curing molding
HexMC-i 2000 is a fast curing high performance molding material. It uses high strength carbon fiber and fast curing HexPly M77 prepreg to assemble a randomly oriented rectangular prepreg 'chip' into 2000 grams per square meter. Composite material for subsequent compression molding.
For R8 X-Brace, Mr. is a foam-filled, drawn-wound carbon fiber tube that is then overmolded with HexMC-i 2000 carbon/epoxy molding to produce a central node for direct mounting to the car. And end parts.
One of the toughest challenges in X-Brace development is how to cure the molding compound without compromising the cured material, and to ensure that it is thin-walled (<1mm壁厚)碳管的最强粘合性。根据制造商的说法，Hexcel的HexPly M77树脂体系具有非常高的粘合强度，可以在两种材料之间产生很强的粘合力，且不会对管子产生过度压缩。
Not only that, Secar and Hexcel also optimize the curing cycle for tool loading and pressing, providing an optimal process parameter for the HexMC-i. Compared to conventional aluminum alloys, when using M77 fast curing epoxy, the part quality is reduced by about 15%.
All metal inserts for X-Brace are molded directly into the part during the production process, thus significantly reducing the number of finishing operations of the demolded parts and saving production costs.
Another advantage of the HexMC-i is that due to the random orientation of the prepreg 'chip' in the material, combined with precise cutting, a unique and attractive visual effect is obtained, which is also Audi's choice of materials. Another key requirement on the top.
Bond strength test
After Secar produced the first prototype parts, Audi brought it back to its own laboratory and performed rigorous static and dynamic load tests on new components at room temperature and in hot and humid conditions. One of the most important concerns for customers is Whether the part can be firmly bonded to the drawn tube. According to the Hexcel report, although no adhesive film or additional adhesive is used between the pipe and the HexMC-i molding compound, all current tests are presented. Satisfactory results.
Successfully obtained Audi qualification
The lightweight technology and one-shot molding process of the new composite X-bracket jointly developed by Hexcel and Secar have finally been recognized by Audi.
'We are pleased that the HexMC-i overmolding process has been successful in Audi's parts and is expected to introduce more advanced technology in the near future,' said Achim Fischereder, Director of Automotive Sales and Marketing at Hexcel.
'Combining the unique features of the HexMC-i product with our high-performance wire drawing and traction technology will undoubtedly be the best solution for significantly improving vehicle performance.' Secar Technologie Sales and Marketing Director Werner Stoeger added.