Lightweight, modular urban electric cars

EVOLUTION (The Electric Vehicle revOLUTION enabled by advanced materials highly hybridized into lightweight components for easy integration and dismantling providing a reduced life cycle cost logic) is using the Pininfarina Nido concept car as a reference for its activities. The existing concept of the Body in White (BiW) has been completely reviewed through a design strategy aiming to reduce the number of parts and using innovative lightweight materials technologies.

The selected body archetype with a central cell is a consolidated standard considering the assembly process scheme, in order to easily shift from low to high production volumes. Basically, the cell has a structural function, while the front end is dimensioned to absorb energy during a front crash and the rear end is conceived to be modular, allowing the transformation into van and pick-up versions.

The considered Al technologies applied on Al 5xxx-6xxx and 7xxx alloys provide the opportunities to obtain parts with complicated geometries and low thickness, merging different parts into one unique element. Besides, it is possible to process one element with a single operation and variable thicknesses.

A “green sand mould” technique allows to obtain co-casted joints between different elements produced with different manufacturing processes.

The potential cost reduction and process simplification in terms of time and assembly are promising: current state-of-the-art, based on traditional moulds, does not allow these opportunities.

The BiW has been hybridised in certain area of the underbody with a composite material of the PA family, reinforced with GF. This material has been obtained improving existing materials and developing a production process suitable for scaling to commercial requirements, throughout an advanced sheet thermoforming and 3D-injection method (CaproCAST process).

Novel polypropylene nancocomposites (pnc) based on layers silicates and glass fibres demonstrate improved toughness and stiffness and have been selected for crash cross beam and side door demonstrators. Polyurethane foams based on recycled polymers are explored for use as sustainable energy-absorbing fill in cross beam sections.

Structural epoxy adhesives have been considered to join the BiW parts and welding points has reduced in number: in certain areas spotwelds have been used only to tack the parts during polymerisation.

In addition to the previous results, current weight of the BiW is 115 kg versus 160 kg of the baseline car. An FE-analysis on the virtual full vehicle puts in evidence a good structural behaviour, considering EU crash standards of homologation and global static and dynamic performances.

The innovative architecture and the integration of lightweight materials will ensure that the EU maintains its competitiveness against the Asian and United States automobile industries.