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Huntsman Advanced Materials has supported University Racing Eindhoven (URE) in an innovative project which sees the development of a hybrid composite wheel which will feature on the team’s electrical powertrains prototype in this year’s Formula Student competition.
For a number of years, Eindhoven University of Technology has been involved in designing, building, assembling and racing a new prototype car for Formula Student.
Viewed by the international motorsport industry as the standard for engineering graduates to meet, Formula Student is widely regarded as Europe’s most established educational motorsport competition, run by the Institution of Mechanical Engineers.
Over the past three years, the URE team has focused on manufacturing racing cars with electrical powertrains systems to take part in the competition’s static and dynamic events. These include elements such as acceleration, skid pan, autocross and endurance as well as static events covering design and cost reports, business plans and fuel economy.
This year a delegation of the URE team, consisting of four Mechanical Engineering bachelor students, came up with a new concept of hybrid composite wheel, designed to help lower the weight of its latest electrical powertrain prototype and achieve an even greater power-to-weight ratio than previously achieved in any of the earlier Student Formula prototype projects.
Manufactured with an aluminium core, the other major feature influencing the wheel’s design and performance is the carbon fibre reinforced plastic (CFRP) shell of the wheel rim. This project highlights the ever-growing importance of high performance composite materials in supporting the drive to decrease manufacturing costs while enabling the development of innovative, advanced automotive design concepts.
The fabrication process represented a key consideration for the team when developing their business plan, who wanted to find an infusion epoxy system that would support their aim to achieve both cost and time savings in producing the composite shell rims using simple manufacturing methods. The selected infusion system would also need to offer enhanced mechanical properties to enhance the strength of the finished rim, while helping to lower the weight of the hybrid wheel and offer high temperature resistance.
The search led to the selection of an epoxy based resin infusion system from Huntsman Advanced Materials which is ideal for producing advanced composites using vacuum-assisted resin transfer molding (VARTM), as well as other infusion processes.
Once the molds for the wheel rims were milled and polished to create a smooth surface, they were then cleaned and a release agent was used. Dry CFRP plies were then draped into the molds in good orientation. Following this, peel ply, flow mesh, release film, breather and tubes for the epoxy resin flow were applied.
The last step involved vacuum bagging the molds in preparation for the vacuum assisted resin transfer molding (VARTM) - a simple manufacturing method which is reliant on high performance technologies with advanced processing capabilities for manufacturers to benefit from reduced investment costs and excellent results.
To meet all the VARTM requirements, the infusion system needed to have a very low viscosity, sufficient pot-life and good fibre impregnation capabilities to successfully infuse the dry CFRP fibres.
In meeting these technical specifications, the infusion system allowed the team to easily control the resin-to-fibre ratio during the VARTM process to achieve the right balance of these components in the final product. This leads to increased strength as well as predictable performance and integrity of the finished part.
Designed with both enhanced mechanical and processing properties, Huntsman’s infusion system helps to create a composite wheel shell rim that is lightweight, robust and capable of achieving an exceptionally high heat deflection temperature in excess of 220°C following an appropriate post-cure.
“The low viscosity and high temperature resistance of the system from Huntsman matches the team’s needs perfectly, helping us to easily manufacture the hybrid wheel using a simple, cost-effective and timely system for processing and manufacturing while delivering a robust wheel rim which will support the car well during the upcoming Formula Student competitions.
Huntsman’s infusion system offers outstanding durability when exposed to high temperatures and this is particularly beneficial as the brake discs on the electrical powertrain will get extremely hot during race conditions. The rims will also have to withstand the forces generated by cornering, braking, bumping and acceleration of the car as well as that which is applied on the tyre changer,” commented Jorrit Goos, Technical Manager at the Eindhoven University of Technology.
The team had a timescale of four months to complete the project, at which point they delivered a case study report covering all elements of the design from start to finish. Thanks to the advanced processing properties of Huntsman’s infusion system in supporting the use of simple molds and VARTM, the CFRP wheel rims were developed within an eighth of that time.
In previous years the URE team used wheel rims weighing 4kg each. The new rims weigh less than 2kg, reducing the overall weight of the 230kg car by an impressive 4%.
“The hybrid wheel project has exposed the students to the latest manufacturing techniques and high performance composite materials, giving them insight into how composites are set to play an even bigger role in the next generation of automotive designs as they prepare to make the move from university to the workplace” continued Jorrit Goos.
The CFRP rims will first be used on the electrical powertrains prototype when the URE team competes in the Formula Student UK from 13 to 15 July.