PulFlex – PulBraiding and bending of thermoplastic fiber composites

The PulFlex project is dedicated to developing a novel process chain for manufacturing curved, continuous fiber-reinforced thermoplastic composites. The aim is to produce a crossbeam made of thermoplastic glass fiber-reinforced plastic (GRP) for high-voltage power lines that is not only lightweight and durable, but also fully recyclable.This involves combining two key technologies: PulBraiding for producing complex fiber architectures and a bending process that enables shaping after production. Implementation is taking place as part of a Eurostars project in an international consortium: CIKONI GmbH (Germany) – project coordination, responsible for simulation and virtual process development. BIRKA COMPOSITES S.L. (Spain) – Application partner specializing in PulBraiding and composite cross-arms for power poles. Fraunhofer IGCV (Germany) – Research partner with expertise in pultrusion, bending, and material characterization.

PulFlex not only creates a new generation of power pole crossarms, but above all a continuous process chain for the production of lightweight, formable, and recyclable thermoplastic profiles. The project combines material development, bending, and simulation into a holistic approach that significantly facilitates industrial implementation. The result is a process that is efficient, sustainable, and flexibly transferable to various applications—representing an important step toward forward-looking composite technologies.

The energy infrastructure is facing profound change: the demand for lightweight, durable, and low-maintenance components is growing, especially in the context of electrification and grid expansion. Conventional metal crossbeams are heavy, susceptible to corrosion, and costly to install. Thermoset composites also offer good mechanical properties, but they are not thermally formable and are difficult to recycle. This is where PulFlex comes in: with thermoplastic GRP profiles that can be bent, recycled, and adapted to specific applications.

Forming:

The thermosetting materials used to date cannot be formed. To avoid joints, the new thermoplastic profiles must be bent—a process that is not yet technologically mature.

Recycling:

Thermosets are hardly recyclable. Thermoplastics, on the other hand, offer the possibility of reusing components after their life cycle.

Development efficiency:

Without simulation, bending is experimentally complex, as fiber repositioning, creasing, and stress distribution are difficult to predict. Simulating the bending process significantly reduces development time and the number of experimental trials, as virtual tests can be used to exclude or specifically select certain configurations in advance.

PulBraiding:

Production of continuously fiber-reinforced thermoplastic profiles with specifically designed bending zones. The combination of braiding and pultrusion enables precise control of the fiber architecture and thus the mechanical properties.

Bending:

After pultrusion, the thermoplastic profiles are heated and shaped into the desired geometry—without any metal connecting elements. This reduces weight, assembly costs, and potential weak points in the component.

Simulation:

At the same time, project partner Cikoni is developing a simulation model that maps the bending process. This enables the prediction of fiber rearrangements, creasing, and springback, thereby significantly reducing the amount of experimentation required. The simulation also serves to optimize layer structure and bending radii. Another focus is on the further development of a thermoplastic resin system that offers not only high mechanical performance but also flame retardancy and electrical insulation – essential requirements for use in energy infrastructure. Material development is accompanied by comprehensive characterization, including mechanical testing, flame retardancy testing, and electrical breakdown strength testing. 

A key objective of PulFlex is to ensure that the components developed are recyclable. An accompanying study is investigating how the thermoplastic profiles can be shredded at the end of their life cycle and reused in injection molding. The properties of the recycled materials are being analyzed and potential follow-up applications identified—an important contribution to the circular economy in lightweight construction.

At the end of the project, a demonstrator will be produced: a curved crossbeam for electricity pylons that proves the industrial feasibility of the developed process chain. In addition, the transferability of the technology to other industries will be investigated – for example, in aviation, automotive engineering, or architecture, where similar requirements exist in terms of weight, formability, and sustainability.