Within a joined project a lightweight, self-joining sill reinforcement concept has been developed. Structural body inserts – SikaReinforcers - act as adapters to fix a steel rolled profile inside the sill and the pillar nodes. Thus, the cost intensive aluminum profile frequently used in current vehicle structures is circumvented, and the complex joining process is essentially simplified.

Sika was a partner in the joined project ECoS « Electric vehicle: Crash-optimized sidefloor structures», conducted by Automotive Center Südwestfalen

This study was concluded successfully at the end of 2021. Project target was the virtual development of innovative sill reinforcement concepts for underfloor battery protection in crash cases. Reference solution is a steel shell structure with a multichamber aluminum extrusion profile, representing today’s state of the art. 

This functionally mature technology implicates high costs and the challenge of joining: such long parts with different coefficients of thermal elongation exhibit several millimeters of relative displacement when passing through the e-coat baking process (delta-alpha problem).

The novel combination of two established technologies shows equal crash performance at lower weight, circumventing the delta-alpha problem and with simplified joining process. SikaReinforcers - fibre reinforced polymeric body inserts - act to fix a steel rolled profile in the rocker’s steel shells and, in the A-pillar node. 

The latter creates a flexural resistant end support of the steel rolled profile which enhances its bending behavior; furthermore, the body response in other crash cases as IIHS frontal small overlap (SORB) is improved. In addition to the connecting function, the SikaReinforcers provide local stiffening and contribute to crash energy absorption. The expandable structural foam component of the SikaReinforcers joins steel shells, body inserts, and steel rolled profile, essentially simplifying the joining process.

The concept is applicable in other body parts as well. The concept is also usable with other sill constituents (such as aluminum panels or fibre reinforced composite shells or organosheets) and other internal reinforcement profile constituents (such as an aluminum extrusion profile or a polymeric extruded or pultruded profile).

Link:  Automotive Center Südwestfalen

Full vehicle with roll formed profile (blue) and SikaReinforcer 2-component structural inserts (yellow, red)

Rocker with steel shells (grey), roll formed profile (blue) and SikaReinforcer 2-component structural inserts (yellow, red)

Detail roll formed profile (blue) and SikaReinforcer 2-component structural inserts (fiber reinforced nylon - yellow, expandable structural foam to bond insert to roll formed profile and steel shells - red). Displayed is adapter part along profile and A-pillar end piece

Cross section adapter: rocker with steel shells (grey), roll formed profile (blue) and SikaReinforcer 2-component structural insert (yellow, red)