Composite bonding boosts Polestar 1 electric performance hybrid
Case Study
Project
Combining multiple substrates to create lightweight yet durable vehicle bodies packed with distinctive design features can be a challenge. This is exactly what Volvo’s new electric performance brand, Polestar, aimed to do in its first innovative model—the Polestar 1 electric performance hybrid.
The new vehicle features an upper body of carbon fiber reinforced plastic (CFRP) and steel composite—Kevlar® fiber can be up to 10X stronger than steel* on an equal weight basis. —which enables the weight reduction that is critical to better fuel economy and battery performance. CFRP also makes the vehicle body more rigid, creating more responsive handling—a must-have for the performance market segment.
However, composites can be difficult to bond. So Polestar turned to DuPont and we put our expertise in composite bonding to work.
Challenges
Polestar’s engineers needed an adhesive that enabled a significant reduction in vehicle weight and noise, and protected against corrosion. Also important was the need to maintain design flexibility while achieving processing, performance, and sustainability goals.
The Polestar vehicles were prototyped in Sweden and manufactured in China under a tight launch deadline. DuPont needed to come up with the right product and be agile and efficient in delivering it.
Design features of the CFRP and steel composite components that comprised the body structure resulted in bond gaps due to varying part tolerances. The bonding material effectively fills those gaps utilizing either hand-held or robotic application equipment with cure and handling strength optimized to work in the Polestar assembly environment.
Solution
For Polestar, DuPont’s BETAFORCE™ 9050L composite bonding adhesive was the material of choice for bonding CFRP panels to the steel composites.
Support for the project during the first prototype builds in Sweden was critical to the success of the project. Similarly, development of a tailor-made heat-curing process at DuPont laboratories in Switzerland helped deliver a heat-accelerated formulation that was crucial to achieving the handling strength needed within a short process time.
DuPont application development experts also helped establish the bond width parameters and partnered with Atlas Copco to determine the ideal position for the adhesive bead on the car body. This ensured that everything would fit together properly during the curing, handling and assembly timeframe parameters.
Results
To keep the project on track and ensure maximum results, DuPont personnel were involved from the beginning. Our team assisted on site with the commissioning of the material pump station, trained operators, and provided other process support, including correct pre-treatment of CFRP before the application of the adhesive.
“The ability to use CFRP–steel composite construction bonded by DuPont adhesives helped reduce vehicle weight by 300 kg, while also meeting the high standards for noise reduction and corrosion control,” said Dr. Andreas Lutz, R&D Director, Adhesives for DuPont. “With 50 meters of adhesive used on each vehicle, we are proud of the strong role we’ve played in the rollout of this innovative and exciting electric performance vehicle platform.”
Why choose BETAFORCE™?
Developed for high-performance bonding in lightweight multi-material vehicles, BETAFORCE™ composite bonding adhesives from DuPont:
- Enable reduction in wall thicknesses
- Allow for optimization of substrates and adhesive joint structure
- Feature stable torsional stiffness over operational time windows that enable effective management of differential CLTE, even on long bond lines
- Enable process time reduction and significant investment savings due to very fast acceleration capabilities
- Reduce process complexity due to primerless performance
- Provide a corrosion barrier between dissimilar materials
- Reduce noise, vibration, and harshness while improving crash performance
- Exhibit a broad range of mechanical and product properties
- Have very good bead stability during application
*Results may vary as there are multiple types of steel with varying tensile strengths and multiple types of Kevlar® yarn with varying tensile strengths.