The Safe Light Regional Vehicle (SLRV) was developed by the German aerospace center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) as part of the research project Next Generation Car (NGC). It addresses concerns about the safety of today’s lightweight microcars with the novel metal sandwich construction. This together with an innovative entry concept, highly efficient H2 fuel cell drive system and crash-optimized chassis were able to achieve the ambitious targets regarding weight (450 kg), safety, energy consumption and manufacturing cost.
The body of the two-seat SLRV is 3.8 meters long and low to the ground, for the lowest possible air resistance. The additionally low weight is crucial for low energy consumption. Even for electrified vehicles with recuperation, up to 93 percent of energy consumption, depending on which point in the drive cycle, is weight-dependent [FRI2010]. A low body mass also enables secondary mass reduction, so smaller and more cost-effective drive components, and its effects [ECK2011].
According to initial simulation results, the SLRV is expected to consume only half as much hydrogen as a conventional fuel cell-powered passenger car.
Sandwich construction: light, low-cost, safe
To achieve the goal of a lightweight and safe construction that is nevertheless cost-effective, the so-called metal sandwich construction (metallische Sandwichbauweise) was developed (see Fig. 2). The materials are composed of metal cover layers and plastic foam as the core. The front and rear sections of the SLRV are composed of sandwich panels and serve as crumple zones [BRU2017]. A large part of the vehicle’s machinery is also housed there.
The passenger compartment consists of a floor tray braced by a ring structure. This absorbs the forces that act on the car while it’s driving and protects the occupants in the event of a crash. With the floor tray, assemblies that are individually found in the passenger compartment of a conventional car body, such as front wall, rear wall, rocker panels and floor, are combined into a single construction element, which significantly reduces the complexity as well as the number of joints.
Similar advantages are offered by the use of the upward-opening canopy in conjunction with a roll bar. With these, the doors, posts, A and C pillars, and roof have been replaced by a single piece. So far, structures made of sandwich materials have not yet been used in the series production of vehicles. The DLR has shown its potential and in the next step is working to optimize the relevant manufacturing technologies.
Crash behavior in the event of a frontal impact
The crash behavior of the SLRV body during a frontal impact was analyzed and documented in accordance with US NCAP guidelines. Such a crash corresponds to an impact of the vehicle against a rigid wall at 56 km per hour (35 mph). The crash box and front end of the SLRV are evenly deformed in the process and absorb the crash energy. The passenger compartment is not deformed, to not reduce the survival space for the occupants.
Important for the crash behavior is also the chassis design of the SLRV. The chassis is designed in such a way that the wheels detach in the event of a crash and are guided past the car body [KRI2019]. This way, the passenger compartment is not hit by the wheel and can be more simply designed.
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