Fraunhofer Institute for Machine Tools and Forming Technology
Fraunhofer Institute for Machine Tools and Forming Technology

Processing of hybrid composite materials

Each structural material has specific properties and, therefore, distinct primary fields of application. The increasing requirements placed on components regarding strength, stiffness, weight, and damping behavior can usually not be optimally fulfilled by a single material alone. The intelligent combination of different materials offers significant potential to achieve the required component properties.

In this context, metallic materials are combined with other metallic materials (e.g. tailored blanks made of aluminum and steel) or with polymers or fiber‑reinforced polymers.

Processing of hybrid components

Formable hybrid semi‑finished products typically consist of two metallic face sheets and a polymer core layer. In addition to high specific stiffness, these hybrid materials exhibit excellent damping behavior, resulting in a broad range of applications spanning from the consumer appliances (“white goods”) sector through classical mechanical engineering to the automotive industry.

To unlock the potential of these flat multilayer composites for large‑scale series production, processing using established conventional sheet‑metal forming methods is required – from blank cutting and forming through to subsequent joining of the components. For the robust and efficient design of these processes, we offer long-standing expertise covering material characterization, process planning and simulation, as well as tool manufacturing and component testing.

Manufacturing of hybrid components

The manufacturing of hybrid components made of metallic and polymer materials was originally carried out in multi‑stage processes. In these approaches, the metallic component was first produced, for example by deep drawing, and subsequently used merely as an insert in the injection‑molding process.

The focus of Fraunhofer IWU’s work on the manufacturing of hybrid components lies on so‑called in‑situ processes, in which primary shaping, forming, and joining are combined within a single process step. The resulting short process chains enable more cost‑efficient production of components; however, they also increase process complexity and therefore require robust and well‑controlled process design and process control.

The most important process combinations are presented below.

Process combination of hydroforming and injection molding

This process combination integrates hydroforming and injection molding into a single tool and process. As a result, the lightweight potential of hollow profiles and the high functionality of injection‑molded components can be combined in a single part. In industrial applications, such components are used, for example, as front‑end carriers or cockpit cross members in passenger cars.

In addition to process and component design, the research focus of Fraunhofer IWU is primarily on process control, the cost‑effective realization of composite bonding, and the use of fiber‑reinforced plastic tubes for the hydroformed component.

Process combination of deep drawing and injection molding

The process combination of deep drawing and injection molding offers the possibility of manufacturing deep‑drawn components in a single process step that are stiffened and functionalized by means of injection-molded plastic structures. The stiffening can serve to modify the acoustic properties of the component or to increase its load‑bearing capacity. For further functionalization, threaded inserts, for example, can be integrated. In the deep drawing and injection molding process, the deep drawing operation is carried out first. At the dead center of the tool, the plastic component is then overmolded.

Manufacturing of hybrid sheet‑metal composites in the forming process

The core of Fraunhofer IWU’s work is the manufacturing of hybrid FRP–metal components within an intrinsic manufacturing process. This means that hybridization – the joining of the composite components – is directly integrated into the forming process. As a result, highly efficient yet highly complex manufacturing processes are achieved.

To master these processes, we pursue a holistic approach ranging from component design through material selection and characterization to simulation‑based process design and prototypical implementation. A key focus of our work is the investigation of innovative joining concepts for the optimal design of the interface between the composite components. In addition to conventional FRP materials, we are increasingly using bio‑based natural fiber‑reinforced plastics (bio‑NFRP) as one of the composite components.

Our range of services

Development of tailored process chains for the forming of hybrid materials

  • Characterization of the hybrid materials and their individual components
  • Process design (simulation, fundamental forming trials)
  • Tool design
  • Process control and monitoring

Reference projects

Process combination of deep drawing, injection molding and forming with the melt

The manufacturing of metal-plastic hybrid components is still highly labor‑ and cost‑intensive. Within the German Cluster of Excellence “MERGE”, a single‑step process has been developed that enables the production of hybrid components at low cost.

Efficient lightweight design through intrinsic hybridization

Fiber‑reinforced plastic composites are preferred lightweight materials. However, a remaining drawback is their insufficient energy absorption in the event of failure. Improvements can be achieved by selectively reinforcing the FRP structure with ductile metallic inserts. Using a multi‑scale forming process, such hybrid components can be manufactured efficiently and with optimized properties.

Processing of NFRP using intelligent coating systems

Within the project, multifunctional coating systems were developed that not only reduce wear on injection‑molding tools but also enable the monitoring of process parameters such as temperature distribution and contact areas. The coatings were tested and further refined both under laboratory conditions and in real production environments. In addition, a test rig for optical wear detection was developed, allowing reliable fault identification and the rapid initiation of appropriate corrective measures.