7th December 2017 by Richard Yen
In preparation for the 2018 Altair Enlighten Award, we’re pleased to share some thoughts on lightweight vehicle design and the use of carbon fiber reinforced plastics from Toyota, the 2017 Module category winner.
While at the CAR Management Briefing Seminars this summer, we caught up with JP Flaharty, Executive Program Manager for Toyota Motor North America R&D. In this interview, JP discusses the carbon fiber reinforced plastic material and how it was applied to the 2017 Prius Prime liftgate and the 2017 Lexus LC 500 side and luggage doors to achieve a lighter weight vehicle. He also touches on some of the challenges associated with this type of vehicle development and the trends he recognizes in the industry. You can watch the interview below.
For those that prefer to read rather than watch, here’s a full transcript of the interview. Toyota’s entry for the Altair Enlighten awards is the carbon fiber reinforced plastic inner panels of the Prius Prime liftgate, the Lexus LC side door and luggage door. Generally speaking, the CFRP inner panel can save around 40% weight compared to aluminum in the case of the liftgate and maybe 45% to 50% compared to steel in the case of a side door or a trunk lid. The primary driver for weight reduction is to reduce fuel consumption and emissions, and that’s driven by regulations in the US and around the world. We also recognize that a lighter-weight vehicle has advantages for the consumer– more agility, better performance. And also, by removing weight from the vehicle, we can find ways to add content and features that are more satisfying to the customer.
Toyota’s approach to vehicle lightweighting has always focused on mass efficient design. By that I mean, trying to use just enough material in the structure to achieve the objectives. And by doing that, we can minimize the amount of material, which saves mass and cost. But there are certain situations where we want to reduce weight even further, so then we look at material substitution. Usually, there may be some kind of a cost offset to that. But if we can find other advantages, such as improved packaging or easier operation by the customer in the case of body closures, we can justify that strategy as well.
The mixed material solution that we chose for all three of these closure panels is intended to put the right material in the right place on those designs. Carbon fiber SMC sheet molding compound, which is a material that’s got centimeters long lengths of carbon fiber dispersed within the resin, it yields a relatively isotropic material property and can be formed into complicated shapes. So in the case of the liftgate, the carbon fiber SMC inner panel serves as a structural foundation, and we use polypropylene resin for the outer panel. In the case of the side doors on the LC 500, we use aluminum for the outer panel. And in the case of the decklid, we use a glass fiber reinforced SMC. And in each case, we chose those materials for the right balance of cost and styling.
We did use simulation technology for the development of the closure panels. We use what we call CAE for strength and durability and usability requirements. A unique simulation approach was used also on the Lexus LC side door because of the speaker. So we actually did some simulation of audio performance, where we were able to make some adjustments to the inner panel to try to tune that performance.
When I learned that we won the Enlighten Award, I was quite frankly surprised. I didn’t expect to win. I would recommend other auto manufacturers and technology companies get involved with the nominations for the Enlighten Award. So much of the difficult work is done in the background to achieve weight reduction, and so any opportunity to get recognition for the engineers and the scientists that are working on these problems is definitely a good thing.