Towards a cohesive methodology for sustainable materials selection in multi-material systems

Although the relevance of sustainability is widely accepted, today´s markets are swarmed with unsustainable products. The underlying reason is the fact that industrial practice has not incorporated eco-design to a sufficient... [ view full abstract ]

Although the relevance of sustainability is widely accepted, today´s markets are swarmed with unsustainable products. The underlying reason is the fact that industrial practice has not incorporated eco-design to a sufficient extent yet (Hübner 2012). Among others, materials selection is a major factor of influence on the sustainability of products (Ashby 2013). In practice, however, decisions on the selection of material are often made based on the product´s predecessor and the designer´s experience rather than well-founded analysis. Especially regarding the multi-material systems used in lightweight design, a methodical approach to materials selection has not been established yet. Commonly used product development processes (PDPs) lack adaption to the requirements and focus of specific design tasks. This is especially relevant to the consideration of sustainability aspects in early stages of product design.
There are a lot of different methodologies covering sustainability analysis and eco-design. Yet, they are not used in practice due to applicability issues. A cohesive methodology is needed to choose the right tools and to implement them in the PDP. This research aims at developing a suitable framework as well as feasible toolsets for sustainable materials selection in multi-material systems.
In this paper, tools for sustainability assessment are identified and analyzed regarding their scopes and resource requirements, within the area of conflict between the three design goals: functionality, cost efficiency and sustainability. Furthermore, three different process models for product development are analyzed regarding their efficiency and compatibility to a topology optimization. To provide an applicable PDP, the producer´s requirements and preferences need to be considered as well. Available resources need to be assigned according to the design goal preferences. By analyzing the individual profile of the three conflicting design goals, a suitable combination of methodologies and tools is identified. The preference profiles are determined by a pairwise comparison of key indicators representing these design goals. The relative focus is categorized in four levels: low, medium, high and maximum. For the design goal sustainability, toolsets for each focus level are elaborated and described. A generic PDP is developed; each module of the PDP is described and the interfaces to toolsets representing the design goals are defined. The structure of the PDP is adaptable to the preferences identified in the triangle of design objectives. Depending on the available resources as well as the relative focus on sustainability, appropriate toolsets can be selected.
The suggested approach is applied on the design of a car door. A sub-system in the waist rail area is investigated in detail. For three different sets of preferences, materials selection in the early stage of the development process is conducted using the suggested methodology. By selecting different materials, the embodied energy of the generic steel part is reduced by up to 76%. The full paper will provide more extensive data, also featuring preference-dependent rankings for the material options.
In conclusion, the approach contributes a suitable methodology to integrate sustainability considerations into materials selection. Thus, the framework provides every enterprise with a promising fundament to efficiently establish purposive eco-design.