Obviously, Geely’s acquisition of Volvo has not detracted the company from its innovativeness. On the contrary: From 2019 on, only electrified vehicles will be on offer. In addition to the drive technology, the company also relies on innovative lightweight design – at least in the external presentation of the Polestar 1. But is the lightweight composite design really up to date in regard of automotive composite technology or is it even innovative?
Thomas Ingenlath of Volvo recently presented the new vehicle concept in Shanghai. It will be built on the Volvo 60 Series Scalable Platform Architecture (SPA), with up to 50% of the vehicle being new developments. An important aspect concerns the CFRP hybrid design, which is implemented with CFRP patches between the underbody and the rear area. Towards the front there is a connection to the battery carrier. To the side, the so called “Dragonfly” stiffening element is supported by the side frame. The separately manufactured carrier is bonded to the steel base plate and is claimed to result in a stiffness increase of 60%. In addition, a separately manufactured, braided component stiffens the roof frame from the A to the B pillar and lies between two sheet steel parts. Another strip supports the side walls above the windshield with an extremely narrow cross-section. Since the cross-section is not constant, it is assumed here to be a double shell construction. In addition, several carbon visual components decorate the interior of the vehicle.
Advantages of the hybrid construction are claimed to be the following features:
- A weight reduction by the CFRP hybridization of 230 kg and the associated range increase for the electric vehicle
- An increase in body torsional stiffness from 22 N/mm² to 32 N/mm²
- A more attractive design due to the thinner walled cross-sections
- A lower center of gravity with better vehicle handling
Thus, the core targets in “Automotive Composites Design” are fulfilled here – but what about additional functionalization of the fiber composite components and the basic design strategy?
The vehicle concept is very reminiscent of the “carbon-core” concept of the current BMW 7 Series. Especially the stiffening of the roof frame with braided components, the transverse support in the roof segment and the hybridization of the ground segment suggest a comparable (or copied?) design philosophy. The carbon visual elements in the interior will probably be manufactured inexpensively in an autoclave process in the country of origin of the owner and do not represent an outstanding technological claim.
The trend to hybridize the steel shell may be considered as an intelligent material mix of the future, where carbon fiber composite components are used only in anisotropic load areas. For the contemplated quantities of only 500 vehicles a year, this is certainly an acceptable level of technology. If, however, an affordable fiber composite lightweight construction should also gain a foothold in larger automobile series, the development should be based on low-cut-waste, semi-finished direct processes. This approach has unfortunately not yet taken place. The vehicle is thus certainly at the forefront in terms of lightweight construction and sets itself straight in comparison to the more conservative OEMs, but just does not represent an avant-garde in terms of composite design or manufacturing technology.