Lightweight engineering is concerned with the aspects of component structure, material and manufacturing processes - and their interaction. Simulation and calculation are used to create component structures that are suitable for the loads which they are subjected to, taking into account the material and manufacturing process. The potential of lightweight construction to reduce costs lies in the interaction of these aspects.
Industries, product applications
Cars, motorcycles, racing, trucks. To meet standards, legal requirements and increase transport capacities (truck/aircraft).
- Exterior body parts (doors, bonnets, tailgates, fenders, spoilers)
- Interior (Seats, interior trim, load floors, shelves)
- Support structures (cross beams, roofs, floor assemblies)
- Covers (underbody panelling)
Aviation / aerospace
Mobile devices and components
- Medical devices: Emergency physician stretcher, couch, bar
- Gardening and agriculture: gardening tools
- Household: cleaning equipment
- Transport containers / pallets / packaging
Sports, Outdoor, Leisure
- Bicycle components and equipment
- Helmets (motorcycle helmet, ski helmet, climbing helmet)
- Ski poles / hiking poles
- Musical Instruments
A lightweight construction always brings advantages when one or more of the following points are decisive:
- Improvement of energy efficiency
- Ease of use
- legal compliance
Aspects of lightweight engineering
The component structure is dimensioned and designed to withstand the load from the very beginning of the design process. Topology optimization is the basis of this design compatible to the respective loads. For this CAE simulation, complete information must be available on
- Installation space
- Defined loads/load cases
- Boundary conditions
In lightweight construction there is often talk of "future materials". These are high-performance fiber composite plastics such as CFRP (carbon fiber reinforced plastic), GFRP (glass fiber reinforced plastic) and continuous fiber materials (continuous fiber reinforced thermoplastics). In general, materials such as tapes, carbon, carbon fiber, Kevlar and biocomposite materials are used.
Organic sheets are also used as thermoplastic semi-finished products. They are being overmolded with thermoplastics for functional integration. The starting material and the overmolding can be combined hassle-free.
Metallic materials are another group of lightweight construction materials: aluminum, magnesium, titanium and high-strength steels are suitable for lightweight structures. However, they are usually more cost-intensive than raw materials.
Plastics technology also plays a role in lightweight construction. Modern high-performance plastics are increasingly suitable for lightweight constructions.
There are different manufacturing processes in the lightweight construction sector, having different effects on component properties. The costs of tools, for example, also vary. Some typical manufacturing methods are:
- RTM (Resin Transfer Molding), HP-RTM
- CRTM (Compression RTM)
- SMC (Sheet Molding Compound) - for processing thermoset materials. Requires reworking e.g. at edges and joints
- CCW (Crush Core Wetpressing)
- Mucell process
- Water Injection Molding
- Injection molding for large series
- Thermoforming - suitable especially for smaller series (for economic reasons)
Processes of generative manufacturing or "additive manufacturing" are considered to be "dreams of the future". Additive manufacturing allows for high degrees of freedom in the component structure ("complexity for free") and any number of variants ("variants on demand"). In principle, it is a kind of "3D printing of structural components". This allows for more freedom in design and development and goes as far as tool-less production or manufacturing without set-up times.
Exemplary processes are
- Selective Laser Melting (SLM)
- Fused Deposition Modelling (FDM)
- Stereolithography (SLA)
- Selective Laser Sintering (SLS)
In lightweight construction, the development process differs from the "conventional" construction method. The basic component structure is largely determined by simulation, even before the actual construction or component design: Topology optimization calculates the force flows within the installation space based on the load cases and the resulting material distribution. This is the basis for the component design or component structure. In this way, a load-compliant design is created right from the start.
A prerequisite for this is that all load cases are known already at the beginning of the design phase: When do which load cases occur? Do load cases act simultaneously? Are all load requirements for the component known? Only if all load cases are available for the calculation, it is possible to avoid oversizing.
The parallel consideration of different materials and manufacturing concepts is also typical for lightweight construction.
Challenges and risks in lightweight construction
Economy / Cost
Little is still known concerning some process and material issues in lightweight construction. Therefore, the cost can depend significantly on individual procedures. Essentially, the following areas are concerned:
- Component/unit cost
Development & Design
- A mere 1:1 substitution with existing components (metal substitution, metal replacement) is often not feasible. Instead, the overall concept must be considered.
- It is crucial that all requirements for the component are known. All processes and loads during transport, handling and processing must be included.
- In some manufacturing processes, experience is less extensive in comparison with other, established and conventional manufacturing processes.
- The availability of some materials is partially limited. Certain orders of magnitude in series production may therefore not be feasible at all.
- The number of possible suppliers, both for materials and production, is also limited in some cases.
Life cycle assessment, failure assessment
In lightweight construction, the question how damage to components and entire products can be assessed often arises during the product life cycle . Which method can be used to determine whether a repair is possible or whether a part or component must be replaced completely? The replacement of parts or components must be taken into account in the design & development from the very beginning.
How to deal with damaged and destroyed components? Are there possibilities to use the raw materials economically again?
Lightweight engineering made in Aachen
M.TEC is a founding member of the AZL (Aachener Zentrum für Leichtbau - Aachen Centre for Lightweight Engineering) and is regularly involved in this lightweight technology network in the vicinity of RWTH Aachen University.