A concept vehicle engineered by Clemson University graduate students features a curved glass roof with a multi-material support structure produced by a novel manufacturing technique.
Making its world debut at the 2016 SAE World Congress in Detroit, the driveable concept uBox vehicle is the capstone of the project, code-named Deep Orange 6, a two-year collaboration between Clemson’s International Center for Automotive Research (CU-ICAR) and Toyota Motor North America.
“This is a very hands-on, immersive program with a goal to prepare the next generation of automotive engineers through real world experience that mirrors an OEM’s full vehicle development process,” Deep Orange 6 project leader Mark Benton told Automotive Engineering at the uBox's unveiling. He added, “The biggest take-away for me was working alongside engineering professionals while still in school.”
Deep Orange 6’s uBox development team consisted of 16 Clemson students and two ArtCenter College of Design students.
The opportunity for engineering and design students to work together while developing and building a vehicle is a valuable experience, said Geoff Wardle, Executive Director of Graduate Transportation Systems and Design at Pasadena, CA’s ArtCenter, “They get to understand the viewpoints of other disciplines, and they learn the art of negotiation.”
Twenty different technology and supplier companies provided products and/or financial aid in addition to mentoring the team that designed, engineered, and built the uBox. The vehicle showcases a curved glass roof supported by composite carbon fiber rails bonded with aluminum.
The support structure is crafted via a pultrusion molding process in which reinforced composite fibers are saturated with a liquid resin, then pulled through a heated die to form a part.
In automotive production applications, pultrusions are used for straight, constant cross-section parts, such as tubes, box sections, U-beams, and I-beams. But the concept vehicle’s roof pultrusion represents an industry-first, according to Dr. Paul Venhovens, endowed chair for automotive systems integration at CU-ICAR.
The support structure, produced by Diversified Structural Composites, is a two-shell constant radius curved pultrusion with a longitudinal roof member cross-section.
“Since the uBox’s roof shape is curved front to rear, a straight structural member would not work,” explained Venhovens. The uBox’s constant radius pultrusion follows the curved shape of the roof.
CU-ICAR graduate students were responsible for the structural roof’s part design, including geometric vehicle integration. The engineering students also determined the functional layout of the pultruded roof members, including torsional rigidity and roof crush test compliance. And they handled system assembly. Toyota management supervised and approved the technology implementation as part of the Deep Orange 6 project.
“The pultrusion process shows great potential for mass production of lightweight and strong composites due to its advantages of dimension stability, relatively short tooling lead-time and its high degree of automation, which is desirable in the automotive industry,” Venhovens explained
Assembling and bonding together both shells of the pultruded roof member, then joining those shells to the aluminum node structure represented a significant technical challenge.
According to Venhovens, structural adhesives were used to bond the pultrusions to the aluminum (node) support structure. Injection adhesives were applied using a pneumatic pistol to push the adhesive through an injection hole into the flange. He said the process required a constant gap distance—realized through machined flanges on the aluminum nodes—between the roof member and the aluminum node structure. It also required adequate venting through venting tubes/holes.
Craig Payne, Executive Program Manager at the Toyota Technical Center, considers the unique roof pultrusion technique to be a very interesting achievement. “While we don’t comment on future products, we continue to look for new development and manufacturing techniques as a form of continuous improvement,” Payne noted.
The all-electric powered uBox’s cabin features a low-floor and reconfigurable, removable seats on sliding tracks. UBox’s vents, dashboard display bezels, and door trim are made from 3D printing technology.