After three years of collaborative research and development, the publicly funded WI-IN research project has been successfully completed. The project brought together industrial and academic partners with the shared ambition of combining Tape Winding and Injection Molding into a single integrated production process. By merging these technologies, the project aimed to enable the efficient production of hybrid hollow structures with reduced material consumption, shorter process chains, and improved sustainability.

Project details:

From Concept to Demonstrator

To validate the new manufacturing concept under realistic conditions, the consortium selected an ambitious demonstrator: a diamond core drill bit for concrete drilling applications.

Conventionally manufactured from steel, drill bits are exposed to demanding torsional, flexural, and axial loads during operation while also experiencing severe abrasive wear. Replacing such a component with a lightweight thermoplastic composite structure represented a significant engineering challenge.

Mitsui Chemicals' Material Technologies: A Key Enabler

Material selection played a decisive role in the success of the WI-IN project. The chosen materials had to meet the demanding mechanical requirements of a drill bit while also supporting the integrated winding and injection molding process and the project's sustainability objectives.

Based on the application requirements, polypropylene (PP) was selected as the primary matrix material for the WI-IN project. PP combines excellent chemical resistance to drilling mud, good mechanical performance when reinforced with fibers, low weight, and excellent recyclability. These properties made it an ideal foundation for the development of the sustainable composite drill bit demonstrator.

Building on this material strategy, Mitsui Chemicals contributed two key technologies to the project: TAFNEX™ PP-CF UD Tape for structural reinforcement and PP-based compounds for the injection-molded functional elements. Together, these materials enabled the development of lightweight, high-performance, and recyclable composite structures.

The project included comprehensive material characterization and application-oriented testing. Wear behavior was characterized using a friction wheel method based on ASTM G611. The results showed a wear rate reduction of at least 50 % compared to the steel reference and, in specific configurations, by up to a factor of ten. As wear governs the service life of the drill bit, these results indicate significant potential for extended durability.

Closing the Loop: Mechanical Recycling of TAFNEX™ Components

To support the project's sustainability goals, recycled PP-based compounds were investigated as an alternative to virgin PP-GF materials. Two recycling streams were evaluated: a closed-loop approach based on project-internal tube waste and end-of-life demonstrator components, and an open-loop approach using sheet-based composite waste from external industries such as mobility applications.

Both material streams were mechanically recycled, regranulated, and compounded into new PP-based materials, demonstrating the potential to reintroduce recycled composite feedstocks into demanding structural applications and support a more circular approach to composite manufacturing.

From Laboratory Testing to Field Validation

The demonstrators underwent extensive laboratory testing, including tensile, compression, flexural, and torsional load cases. The most successful manufacturing concept passed all functional substitution tests, demonstrating that the integrated winding-injection molding approach can meet demanding structural requirements.

The project culminated in field trials under realistic operating conditions. One of the composite drill bits was used to drill multiple holes in reinforced concrete. Despite being the first demonstrator of its kind, the hybrid composite drill bit successfully completed all drilling operations. While opportunities for further optimization were identified, the achieved performance significantly exceeded initial expectations and confirmed the technical feasibility of the concept.

Building the Future of Hybrid Composite Manufacturing

The WI-IN project demonstrates the potential of hybrid thermoplastic composite manufacturing to enhance technical components traditionally made from metal. The validated PP-based demonstrators offer several advantages over the steel reference.

The hybrid thermoplastic design reduces component mass by 65 - 70 %, saving approximately 1.4 kg per drill bit with a diameter of 82 mm and providing a direct ergonomic benefit for hand-guided operation. The excellent tribological behavior of the thermoplastic composite material resulted in a wear reduction of at least 50 % compared to the steel reference, indicating significant potential for extended durability. A sustainable component design, supported by the use of recycled feedstocks, can reduce CO₂-equivalent emissions by 22.5 - 37.5 % when the extended service life is taken into account.

Beyond the specific product, the process combination is broadly transferable. Wherever hollow, rotationally symmetric, or profiled lightweight structures require local functionalization, whether in automotive, aerospace, defense, or industrial equipment applications, the Inside-Molding process chain offers an efficient route to integrate structural reinforcement and functional elements within a single manufacturing sequence.

For more information about TAFNEX™ or the WI-IN project, please contact us via email.