• Lightweight construction in vehicle construction
  Lightweight materials like e.g. aluminum or fiber-reinforced plastics are already used to reduce weight and therefore reduce CO₂-emissions. Especially in terms of electric vehicles, the production and the end-of-life phase become more important concerning the ecological footprint. Therefore, renewable, recycable and/or biologically degradable materials should be taken more into account
• Wood as a lightweight construction material
  Mechanical properties of wood are a high specific strength and stiffness in fiber direction and a high elasticity and energy dissipation transverse to the fiber direction. In the case of crash loads, the specific fracture energy is independent from the temperature (-20 to +80 °C). Wood-based materials offer the potential for weight reduction, a better ecological footprint (including production and end-of-life phase) and at the same time good mechanical performance for structural vehicle applications. By using wood in this context, the weight of crashworthy structures can be reduced by up to 20 %, while greenhouse gas emissions and non-renewable energy intake can be reduced by a third.
• Fire protection through using wood
  Thermal decomposition of wood causes a char layer to form, which protects the remaining cross-section. The superficial charring cuts off the oxygen supply and thus delays further burning. For load-bearing structures, a burn rate of 0.7 mm per minute is expected. Even in fires with temperatures above 1000 °C, the temperature in the wood drops to less than 100 °C only 10-15 mm from the active charring zone. Compared to other building and construction materials, burning occurs slowly and regular. Due to the high thermal stability of the wood structure, there is no sudden structural failure, making the fire event calculable and regulable by the choice of material cross-sections. Whether this applies also to small cross-sections as in the present research project cannot be answered at present and will be investigated in this research project.
• Wood modification and fire protection of wood
  A significant increase of the flash point (400 °C) and reduction of the burning rates can be achieved by wood modification. In addition to commercially available impregnates, water glass can also be used for flame retardancy that is as biologically harmless as possible. However, these approaches have to be investigated with regard to the requirements from the mobility sector (outgassing behavior, burning rate, etc).
• Battery housing
  Li-ion batteries generate heat during (dis)charging processes. Whiloe excessive heat can cause irreparable damage to the battery, very low temperatures will result in poor performance. Therefore, battery systems must be designed to run cells within optimized temperatures (15-35°C) to maximize performance, efficiency, and longevity while ensuring safety. Current and future safety guidelines regarding electric vehicle safety require a warning period of 5 minutes. During this time period, the battery must not pose any danger to the occupant, even if thermal runaway of cells has already started. To extend this period, thermal propagation from cell to cell must be prevented. On cell level e.g. by "shut-down" separators or flame retardant electrolytes. At a higher level (cell stack, module, subpack, pack, battery), the following strategies can be considered on the material side: (1) Endothermic materials, which extract energy from the exothermic TR, e.g., by phase transformation. (2) Highly insulating materials, which reduce heat exchange or increase thermal resistance. As with the vehicle chassis, a scalable and modular design has become established in current battery enclosures. These designs are usually based on a frame, stiffened by an internal lattice structure or cross-member and closed by a base plate with underbody protection and cooling system, as well as a housing cover. The frame usually also contains the mechanical connection points to the vehicle structure. Functional integration is currently being researched to reduce weight. It has been shown that by combining thermal and mechanical properties, a reduction of subshell mass by 23% could be achieved.

• Ecologically effective weight reduction
  • Battery housings are large. Therefore, there is a high potential for effective weight reduction of the overall vehicle and thus for improving the energy balance.
  • Thanks to an advanced integral design, in which several functions are covered by the laminated components at the sdame time, a reduction of the total weight and installation space is achieved.
  • Compared to other common lightweight materials, it is shown that steel-wood laminates offer a balanced combination of low weight, low manufacturing costs and a low environmental footprint over the entire life cycle.
  • Not only technical properties are surveyed, but a holistic evaluation is performed: Cost, weight, environmental footprint, socio-economic effect.
• Functional integration through wood material
  • The favorable properties of wood are widely known and used in civil engineering (thermal insulation, fire protection) and the sport goods industry (high specific stiffness
    and strength, high vibration damping). Taking into account the already existing knowledge from these areas, the concept appears promising.

Wood modification is necessary to ensure a good durability of the wooden product. However, wood modifications as well as good-quality and durable adhesive systems are often expensive. In BioLIB, these challenges are approached as follows:

• Locally restricted and target-oriented wood modification
  Modificated wood is only used in the outer veneer layers where it is really necessary and protects the inner non-modified veneer layers. This way a good durability can be achieved at minimal costs.
• Integrated joining technology