This article also appears in
Subscribe now »

Intrado structure uses CFRP with lightweight steel panels.

Hyundai trials lightweight construction techniques with Intrado concept

Intrado, according to Hyundai, is the area on the underside of an airplane’s wing where lift is created. So it is assumed that the construction of a modern aircraft wing and the use of innovative materials inspired Hyundai to create its latest concept. The Intrado concept shown at the 2014 Geneva Motor Show uses a new construction method that brings together lightweight steels and a strong, rigid, lightweight carbon fiber reinforced plastic (CFRP) structure, and power from a hydrogen fuel cell.

“Here we are focused more on the efficiency of the car,” explained Günter Roos, the Design Engineering Manager at Hyundai’s Design Center Europe in Rüsselsheim, Germany. “So that was important for us to show this combination of fuel cell plus the carbon structure because it has not been done in the industry before.”

Hyundai also wanted to look at new construction methods: “So we didn’t go into the monocoque sheet metal substitute direction. We stepped into the heart of the car and analyzed where is the force flowing in the car. So we looked into a frame, rather than a body,” said Roos. “Our target is to find lightweight solutions, and we believe that cars of the future will still use steel as a decoration, design-defining element and the carbon will give the car the strength. So we will not try to use carbon as decoration. We are going for larger numbers of cars. We’re not going into niche production, so we believe the advantages of steel are valid, and we will take advantage of the combination of CFRP and steel.”

The CFRP used for the structure has been supplied by Lotte Chemical and the carbon fiber was supplied by Hyosung. Hyundai believes that the structure will be more easily repairable than typical carbon-fiber structures because damaged sections can be repaired without using expensive tooling or ovens.

Hyundai plans to build the CFRP structures on a production line: “We focussed on having simple geometries which can be laid out and manufactured by robot,” said Roos.

The concept uses CFRP frames designed for different parts of the structure—for the doors, the roof, a structure to package the fuel cell power source. This combined with the CFRP beams that form the basic structure are expected to be able to provide the strength needed for the Intrado’s structure, which has been designed without B-pillars. Instead a beam runs from the front to the rear of the structure through the center line of the car and would be disguised by the center console. Roos says that the beam increases the torsional stiffness of the structure by 10%.

The CFRP beams can be reinforced with a ribbing structure to provide greater rigidity and crash resistance where needed. Physical testing has yet to be completed, but Hyundai believes the structure will provide the necessary crash resistance.

With the fuel-cell installation fitted low in the chassis, and the batteries fitted beneath the floor, the Intrado has a low center of gravity.

Composite tanks are used at the rear of the vehicle to store over 100 L (3.5 ft³) of hydrogen pressurized to 700 bar (10.1 ksi). The smaller tank is located under the rear passenger bench seat, while the larger tank is fitted beneath the trunk floor. This should give the car a range exceeding 600 km (373 mi).

The 36-kW·h lithium-ion battery pack is used as a buffer to store electrical energy and provide a stable voltage output to the drive motor and electrical systems.

Continue reading »