Interestingly, the Nuna team developed its own production process.
"We started by having the plugs milled to the correct dimensions. These are then covered with gelcoat and, after that, mold resin. These two layers can then be pulled off the plugs to obtain molds for the car. In these molds, we did the final carbon fiber layup by hand using dry TeXtreme fabric and DSM Turane resin."
In the World Solar Challenge, competing teams race from Darwin to Adelaide, more than 1,800 miles away. Based on the idea that a 1,000W car would complete the journey in 50 hours, solar cars are allowed a nominal 5kW-hours of stored energy, which is 10 percent of that theoretical figure. All other energy must come from the sun or be recovered from the kinetic energy of the vehicle.
Once the teams have left Darwin, they must travel as far as they can each day until 5:00 p.m., when they make camp in the desert.
During the journey, there are seven checkpoints, where observers are changed and team managers may update themselves with the latest information on the weather and their own position in the field. Here teams may perform the most basic of maintenance only, such as checking tire pressure.
There are 21 teams entered in this year's event, including the MIT Solar Electric Vehicle Team, the Stanford Solar Car, and CalSol, the University of California/Berkeley Solar Vehicle. Another entry, the Ra 7, comes from Principia College, a liberal arts school in Elsah, Ill. Lack of an engineering department is not a deterrent; the Ra 7 is custom built by Principia students with majors ranging from physics and computer science to English and graphic design.
If the auto industry CAFE is going to reach 54.5 mpg in the next 15 years, it's going to have to draw from a variety of new technologies, including materials similar to these. I would think the high stiffness bodes well.
I understand the stiffness part of the lightweight materials. And I am willing to bet the overall structure is still considerably stronger than anything else on a lb for lb basis. The overall characteristics of these new materials are really impressive in every respect.
I can't wait to see some of these materials and designs formulated for production vehicles and then subjected to crash tests. Eventually the combination of lightweight, stiffness, impact resistance, deformability and strength will be engineered into vehicles capable of protecting the passengers during high impact crashes, probably assisted by air bag devices.
Although the specific strength of the car is still very good, on absolute terms it is not. For example if this car would have a collision with a regular road car then safety is quite a concern.
The materials used are very high tech and at the moment also very expensive, this is why carbon fibre is still mainly used in race cars and high performance road cars. And when carbon fibre is used at the moment, it is usually solid laminate. The problem with this is the same as the problem with high strength steel, thin sheets offer enough strength but are very easy to bend (low stiffness).
This is were sandwich construction comes in, the thin carbon fibre facings are placed outwards and low density foam is used to fill the gap. Because now the thickness is increased, the stiffness is also increased tremendously.
But this technique comes with a price, you basically have a low strength high stiffness structure and this means that impact resistance is not especially high. I am sure that safe structures can be designed light with these techniques, but versus heavy current cars safety is still less.
Use of light weight components will be the way to 54.5 mpg. The wheel configuration is reminiscent of the Dale that was two wheels in the front and one in the back which was supposed to reduce the weight enough to get 70 mpg. Overall, that vehicle was a hoax, but there were some parts of the design that could be used today to get to the 54.5 mark.
The slide show really provides a great look into what's involved in testing and building the composite structure. Great addition, Doug.
Any sense of whether the team is using any composite analysis software to help with the actual design of the carbon fiber sandwich or are they doing it as a hands-on process with manual calculations?
Beth, We do use analysis software for our calculations. Without it, we could have never designed such a lightweight structure. We use software from ANSYS called Composite PrepPost that is based on ANSYS mechanical. Basically we model the car with shells and apply composite material properties on the meshed elements.
Materials can be defined as plies and core materials, which are then stacked to simulate the sandwich construction.
@Woytek Bode: Thanks for elaborating on the role of simulation software. Many organizations using composites still don't tap into analysis software or do so late in the design cycle. Do you use the ANSYS tools upfront in the design cycle or later on in the process as more of a validation tool?
Many oranizations design and develop overdimensioned structures where the use of such software might be not useful yet. We are with thirteen students and only have one year to design and build a completely new solar car. I guess that because we are with so many young engineers, the design philosophy is very different to that of 'old fashioned' companies.
This alone would result in very different methods of designing and also building. But ofcourse also time forces us to finish the final designs quickly so the production process can be started.
The ANSYS package is also used for all structural aluminium and magnesium parts for the suspension. Furthermore, CFD calculations on the aerodynamics are also done in the same suite.
So in conclusion: yes we use these tools upfront in the design cycle. We first focussed on the materials allowing us to build light (TeXtreme, Rohacell foam, Turane resin) and did tests to ensure we enter the correct material data in ANSYS. This allowed us to set detailed demands on the structure and introduce complicated load cases. Also, the weight of the structure can be estimated to good accuracy and this helps us determine the optimum in problems like facing thickness vs. core thickness and solid (L-like) vs. sandwich stiffeners.
Once again, thanks for clarifying. To your point about the team being 13 "young engineers": So you think they are more open to the role of analysis tools early on the design cycle and using simulation in general compared with more established engineers or more traditional engineering processes?
I agree sleek design. Looking at it, there is a wheel in the front and two in the rear. The design is more like a 3 wheelers (similar to scooter). Do you know what considerations drove the design to be a 3-wheelers type? Will this be able to support more than one passenger? I wonder?
Inspired by the hooks a parasitic worm uses to penetrate its host's intestines, the Karp Lab has invented a flexible adhesive patch covered with microneedles that adheres well to wet, soft tissues, but doesn't cause damage when removed.
Engineers at the University of California, San Diego are designing a robotic arm that takes inspiration from the loose, flexible, yet very strong structure of the armored plates on a seahorse's tail.
Researchers at the Missouri University of Science & Technology have designed a new nanoscale material that can transmit light faster than the 186,000 miles per second it usually takes to travel through air.
It has often been said that as California goes, so goes the nation. This spring, the state's wind power is setting energy generation records and solar energy generation is expected to rise sharply during the second half of 2013.
The latest model of Liquid Robotics' Wave Glider autonomous, unmanned marine vehicle (UMV), the SV3, is reportedly the world's first hybrid wave- and solar-power-propelled unmanned ocean robot.
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A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
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