Advanced lightweight design
A joint study investigating the possibilities of further automotive lightweighting in body and closure parts has revealed that about 40 kg of weight per car can be saved if conventional all-metal components are replaced by hybrid designs using high-performance structural foam. The approach leverages the synergy of a specially developed lightweight structural foam technology from Henkel in combination with advanced engineering design by RLE International. Extensive crash simulations have validated the concept.
Bumper beam optimization
The starting point of the study was a radical review of standard component designs that focused on their required rigidity and performance in crash situations. The final designs were arrived at over several weeks of consecutive optimization cycles, including extensive crash simulations and other pertinent testing, as detailed further below.
Figure 1 exemplifies the concept by means of a structural hybrid reinforcement for use in the right and left sections of the front bumper beam. In particular, the solution also addresses small overlap front crash performance requirements. It reduces the beam thickness to 2.0 mm and saves a total of 1.7 kg per bumper.
Leveraging the synergies
Based on these tests, a weight reduction of more than 10 kg per car can be achieved with optimized hybrid rocker, pillar, bumper and rear-side member components alone.
The structural foam used in the hybrid designs is an epoxy-based Teroson® EP material from Henkel that delivers high strength and stiffness at extremely low weight. The non-cured injected foam is resistant to normal automotive washing and phosphating solutions as well as to electro-dip coating. It cures within 15 minutes when passing through the e-coat oven. The current material technology features a commercially available grade (EP 1450) with extensive approvals from automakers worldwide.
Several OEMs are already using the material in various lightweight hybrid structural parts, replacing traditional steel reinforcements. Further grades are in the pipeline and are being developed with a focus on lowering the cured foam density, increasing the foam expansion beyond 100 percent and reducing the required curing time.