- Website: http://lightweight-alliance.eu/
Affordable Multi-Material Lightweight Design
Overview of the final results of the H2020 project ALLIANCE
In the last years, the research activities in the field of lightweighting have been advancing rapidly. The introduction of innovative materials and manufacturing technologies have allowed significant weight reduction. Despite this, novel technologies and materials have not reached a wide distribution. The reasons for this are mainly high production costs and environmental impacts of manufacturing that do not compensate benefits during operation. Within this context, the European Research Project AffordabLe LIghtweight Automobiles AlliaNCE (ALLIANCE, www.lightweight-alliance.eu ) was initiated aiming at developing novel advanced materials (steel, aluminum, hybrid materials) and production technologies to achieve an average weight reduction of 30 % over 100k units/year, at costs less than 3 €/kg-saved and 6 % Global Warming Potential (GWP) reduction.
Within ALLIANCE, seven physical and one virtual demonstrator(s) were designed mostly in steel and aluminium intensive multi-material approaches as shown in Figure 1. All demonstrator parts are applications for a specific vehicle project of the related partners (OEMs). That means these parts have to fulfill certain specifications depending on the vehicle projects they are developed for. The demonstrators aim to cover the most characteristic parts “archetypes” in terms of production method (forming/deep- drawing, extrusion, casting) and the main functions they serve (crash, stiffness, appearance, NVH, etc.). Although the focus within ALLIANCE was on novel steel and aluminium grades, the rear floor pan was considered in reinforced plastic to cover all relevant material mixes of an advanced multi-material design. In the design phase, standard design tools, as well as the ETWA, were applied to find the optimal concept. Due to the space limit, only selected modules are described in the following.
Figure 1 The ALLIANCE demonstrator modules
To evaluate the impact of the ALLIANCE solutions, a LCA “from-cradle-to-grave” was developed focusing on the Global Warming Potential (GWP) applying a breakdown approach based on vehicle assemblies/modules. As a baseline, the ALLIANCE virtual full vehicle was used representative for both ICE and EV; a life-distance of 230,000 km and 150,000 km over 10 years is assumed respectively for ICEV and EV. Considering that the ICEV and EV have specific usage requirements and duration, two distinct values of LC mileages have been taken into account. The system boundaries include all processes within the vehicle life-cycle stages:
- Materials production stage compels raw material extraction and process to semi-finished product (i.e. ingot, slab, billet);
- Manufacturing stage includes the process from semi-finished product to mono-material part;
- Use stage includes fuel/energy production and tailpipe emissions;
- EoL stage considers car shredder technology, automotive shredder residue processing, materials sorting and recycling.
Figure 2 LCA system boundaries of the reference vehicle
Unlike LCA, there is no standardization of the methodology but only SETAC guidelines describing the main phases but not providing a unique approach for the cost modelling of life cycle stages. For this reason, a specific modelling approach has been developed considering, in particular, the manufacturing phase (including material costs) and use phase. Again, the virtual full vehicle was broken down into modules, which, in turn, are broken down into mono-material parts. The cost of each mono-material part comprised in the full vehicle is estimated according to its specific technical features (material type, geometry, mass, volume, etc.). Secondly, all the processes and subsequent vehicle manufacturing are identified and broken down, including human and physical capital requirements (machinery, tooling, consumables, industrial space, employees, etc.) and related costs. Finally, all costs per part are aggregated, considering the vehicle structure and assembly processes (mono-material parts into modules, modules into vehicle assemblies) to obtain the full vehicle cost. This analysis was performed for both the ICEV and the BEV and it is based on the same boundary conditions assumed for the LCA study.
The final results of the impact assessment for each demonstrator module are shown in Table 1. The assessment is provided only in relative numbers since the absolutes values for each demonstrator module are considered as confidential. Overall considered modules a weight reduction of 31%, a reduction of 25% in kg CO2 eq. at 2.7 € additional costs for each kg saved have been achieved in total. Remarkable is that with a consequent design approach the overall production costs can be lowered for some components.
Table 1. Summary of achievements on component level
|Weight [%]||GWP, kg CO2 eq. |
|Door concept 1 (multi-material)||-29,4||-18,3||+4,37|
|Door concept 2 (aluminium)||-44,1||-43,6||+4,45|
|Rear floor panel||-26,0||-20,1||-4,42|
|Front bumper beam||-12,3||-9,9||+3,18|
|Rear bumper system (EU version)||-39,3||-23,3||-1,55|
|Rear bumper system (US version)||-45,2||-39,2||-0,58|
|Strut tower w. integrated rail||-35,0||-28,0||+1,53|
 The assessment of the CO2 footprint is only valid for the specific component and cannot be taken for the full vehicle.
In order to assess the ALLIANCE technologies and solution on full vehicle level, a virtual full vehicle model has been derived for an ICE and full battery electric vehicle. As final proof of concept, all technologies are scaled and transferred into this virtual ALLIANCE full vehicle model demonstrating that affordable and sustainable weight reduction can also be achieved at the full vehicle level, within the range of the predefined targets while additionally considering secondary weight saving potentials. The virtual vehicle was broken down into different modules (Fig. 3) and an analysis of the technical requirements performed for the individual modules and components and of potential design options regarding material and manufacturing. Based on this analysis the feasibility was assessed towards integrating ALLIANCE technologies into the overall structural concept, the ratio between benefit and effort related to lightweighting and impact on costs and GWP. In a second step, the ALLIANCE material and manufacturing technologies were implemented such as
- Advanced high strength steel and aluminum alloys
- Fiber-reinforced plastics (FRP)
- Metal-FRP hybrids
- Advanced metal forming
- Tailored Extruded Blanks (TEB)
- Hybrid technologies
- Injection Moulding Compound (IMC)
In doing so, lightweight design principles like one-piece solutions or “right materials at right places” were applied consequently. The transfer and up-scaling of ALLIANCE technologies developed on component level resulted in a weight reduction of about 9.4 % on full vehicle level (ICE version). When exploiting also secondary effects additional 6.2 % weight savings can be gained resulting in a total saving of 15.6 %. This directly results in 10 % less energy consumption.
Figure 3 ALLIANCE full vehicle model with considered modules.
Within ALLIANCE affordable lightweight solutions based on advanced steel and aluminium grades and novel conceptual designs have been developed for eight exemplary structural components. Besides, a new approach to assess the impact regarding LCA and LCC on the full vehicle level has been developed. The final results indicate that a significant weight reduction of up to 33% can be achieved while limiting the additional costs below 3 €/kg-saved. When taking into account LCA and LCC aspects already in the conceptual design phase, lightweight solutions can be realised with even reduced costs compared to the reference. The weight savings directly impact the GWP of each component leading to about 25% reduction in GWP on component level. However, the results of ALLIANCE also indicate that some components are already highly optimised regarding weight and radical new solutions might be needed to significantly reduce weight (> 20 %) at an acceptable cost.
The ALLIANCE project clearly showed that lightweighting should not be carried out for the purpose of making cars lighter but to reduce emissions (LCAs in early development stages). Within this context, holistic approaches are required to solve the issues related to lightweighting: a combination of technological, market awareness and ecosystem innovation is crucial. Besides, digital technologies in the design, testing, manufacturing and use phases will become essential to accelerate innovation.
The presented work was funded by the European Commission (H2020) within the project ALLIANCE (Grant agreement No: 723893): http://lightweight-alliance.eu/.
The ALLIANCE consortium consists of: Daimler, VW, Opel, TME, Volvo Cars, CRF, Benteler Automotive, Batz S. Coop., Novelis Switzerland, ThyssenKrupp Steel Europe AG, inspire AG, Ricardo UK Ltd., Bax & Company, Fraunhofer LBF, RISE IVF and Swerim. Karlsruhe Institute of Technology, RWTH Aachen – ika, University Firenzi