Material knowledge as the key to project success
Interview with Prof. Dr. Martin Bonnet, University of Applied Sciences Cologne
Material knowledge is crucial. Why?
Not only across a single class of materials, but also across disciplines: Metals, plastics, glass, and carbon fiber must be understood in order to create truly innovative solutions.
Many industries are not as open to use thermoplastic materials. Why?
Dirk Moses: Plastics and composites play an important role in many industries, from aviation to energy technology, while other sectors, such as the construction industry, are often more conservative. In your experience, why is that?
Prof. Dr. Martin Bonnet: In more conservative industries, a material is often only used once many years of experience have been gained. Fiber composites offer unique specific stiffness and strength properties. Applications only become possible or significantly better when composite materials are considered.
Dirk Moses: There are, of course, advantages and disadvantages to using composite materials. Which issues do you consider particularly critical? What should be taken into account?
Prof. Dr. Martin Bonnet: One classic issue that is often overlooked is the interface between the fiber and the matrix: the fiber-matrix bond. It is not enough to understand the matrix and fiber separately; the forces must be transferred from the matrix to the fiber for the reinforcement effect to occur. If, for example, glass fibers are simply inserted into polypropylene, the properties may even deteriorate without proper bonding. That is why surface modifications, sizing, or other treatment processes are crucial.
What is the best way to ensure optimal bonding?
Dirk Moses: In your opinion, what is the best way to ensure optimal bonding in such combinations?
Prof. Dr. Martin Bonnet: Pultrusion with polypropylene and glass fibers is unusual; many people immediately think of thermosetting systems such as epoxy when they hear the word “pultrusion.” With thermoplastic pultrusion approaches, the challenge is to sufficiently saturate the fine individual fibers with matrix material. The decisive factors are therefore the choice of matrix (operating temperature, chemical resistance), the type of fiber (glass vs. carbon vs. aramid), and the surface treatment of the fiber, such as coatings (sizing) or physical processes such as corona treatment to improve polarity and thus coupling.
Dirk Moses: Technoform deliberately relies on thermoplastic materials because subsequent overmolding, welding, or the use of the same material in the component brings advantages. What additional opportunities does this open up?
Thermoplastics simplify joining processes such as welding or overmolding because you stay with the same material. This also opens up recycling options: in many cases, the product can be shredded and the material reused. However, grain size and the resulting fiber length influence the properties: longer fibers increase impact strength, for example, while shorter fibers can influence stiffness and strength. Different fiber lengths, diameters, and coatings result in a wide range of properties; a component made of polyamide 6 with 30% glass fiber content is not always the same.
Prof. Dr. Martin Bonnet: You primarily use glass fiber and not carbon? Why? Carbon fiber is considered the “Rolls-Royce” when it comes to stiffness.
Dirk Moses: Technoform focuses on glass fiber solutions to create relatively inexpensive targeted stiffeners instead of thicker components or complex rib structures. This enables lightweight construction and material savings, especially in electric vehicles or sports cars, where new space concepts are emerging.
Are there product examples?
Prof. Dr. Martin Bonnet: Can you give specific product examples?
Dirk Moses: Our profiles are used as inserts or reinforcement elements, e.g., in injection-molded and pressed parts. One example would be elements for the front of the vehicle (frunk). A frunk is an element used as a tray in the front compartment of a car. The term “front trunk” becomes “frunk.” The idea is to enable higher load capacity while maintaining thin, lightweight shells.
The aim is to have a shell made of a single material. In this case, the material is polyamide. The polyamide frunk is therefore reinforced with polyamide inserts.
Prof. Dr. Martin Bonnet: Material knowledge is key, not only across a single class of materials, but also across disciplines: metals, plastics, glass, and carbon fiber must be understood in order to create truly innovative solutions. Those who have material knowledge can drive new developments in a targeted manner.