Enhancing vehicle crash performance can entail significant weight increase. But working with PSA Peugeot Citroën, engineered plastic foams specialist JSP has revealed a solution that not only improves crash test performance but also saves weight.
Using ARPRO expanded polypropylene (EPP) for the rear-seat structure of Citroën’s new-generation C3 has provided a 2.2-kg (4.9-lb) savings, allowing engineers to replace a heavy and costly steel structure with a strong, light, and recyclable material.
Crucial to the success of the project, according to JSP, was the ability to demonstrate the crash performance of ARPRO using simple machined parts.
The project was conceived after JSP and PSA presented their analyses of seat design requirements at a vehicle design conference. PSA felt the ARPRO seat concept could work for them but wanted to assess it quickly and with minimal expenditure.
“Our partnership started in 2005,” said Paul Compton, JSP’s President and CEO – Europe. “At that time, we had no other seat applications in production using ARPRO for the anti-submarining structure. We therefore had to demonstrate proof of concept and do it fast to meet the program timing.”
ARPRO’s material properties allow prototypes to react in the same way as molded components. JSP was able to rapidly design and create representative parts using a standard five-axis machine. These were then fitted to the previous-generation C3. A crash test undertaken at UTAC, the French independent technical organization handling certification of systems, concluded that an improvement over the existing steel version could easily be achieved.
“For a very small investment and within a short time frame, we were able to validate the concept in a real crash,” said Compton. “This test, together with the growing relationship between the partners, gave the program engineers the confidence to back the project for mass production.”
ARPRO was demonstrated to be strong and resilient enough to replace the metal anti-submarining ramp (there to help retain rear-seat passengers in their seats in the event of a frontal crash), contributing to a simpler and lighter vehicle structure. Compared to the previous-generation C3 rear seat, switching to ARPRO for the 2010MY vehicle provided Citroën with a metal weight reduction of 1.79 kg (3.95 lb). The balance of the 2.2-kg savings has been achieved via a lower polyurethane content and simpler fastening system, the latter also reducing the complexity and assembly cost.
The ARPRO seat concept will also allow Citroën to simplify the body-in-white tooling, offering the potential for a flat or near-flat load area floor when the rear seats are folded, and to reduce complexity across future shared vehicle platforms.
“Tuning the size and shape of the ARPRO element lets designers adjust the H-point [the vertical location of an occupant's hip, relative to the floor of the vehicle],” added Compton. “We can offer a solution to create seating variants such as a coupe or off-roader that use a simpler body-in-white structure.”
He belies that customer perception—“what customers sense on initial contact”—has also been improved with the new seat design and the use of ARPRO, allowing an increase in material properties such as deformation resilience and molding accuracy.
“The consistency of the molded parts and simpler assembly process supported Citroën’s desire to raise ‘perceived quality’ levels,” said Compton. “Better alignment with visual design features, such as the leather stitching, enhances the customer’s experience.”