The Durohyb project, funded under the German Federal Ministry of Education and Research (grant code 03XP0268C), ran from 1 March 2020 to 28 February 2023. Eight partners collaborated, with DEWE Brünofix GmbH acting as one of the eight contributors. The project’s aim was to develop methods and technologies for designing, manufacturing and testing long‑term operation‑safe metal‑duroplastic composites for highly demanding components. The overall goal was to improve the bond between metal and duroplastic by applying targeted surface pre‑treatments to the metal.
The technical work focused on surface preparation, phosphating, cleaning, coating, and adhesion testing. DEWE Brünofix performed the surface cleaning and phosphating of metal inserts and test specimens. A cleaning protocol was established to achieve a minimum surface tension of 38 mN m⁻¹, ensuring a reproducible starting condition for all subsequent processes. The phosphating experiments investigated three coating chemistries: zinc phosphate, zinc‑calcium phosphate, and manganese phosphate. For 16 MnCr5, 100 Cr6 and S355 steels, coating thicknesses ranged from 0.8 µm to 2.5 µm. In total, 207 sheets were phosphated, and 20–20–17 sheets were used for each coating type in the initial batch. Thin zinc‑phosphate layers produced the best adhesion results in preliminary tests, and laser‑structured surfaces further enhanced bonding, yielding unexpectedly high adhesion strengths. Adhesion tests were carried out at Hexion GmbH (formerly Bakelite) and interface investigations at the Technical University of Chemnitz. The project also produced a demonstrator rotor shaft, a handling line for demonstrator production, and a set of components for the demonstrator. The demonstrator was designed to validate the long‑term performance of the metal‑duroplastic joint under realistic loading conditions.
Only 918 of the originally planned 3 480 hours were executed, representing 26.5 % of the planned effort. The most time‑intensive work package was 2.4, “structuring and modification of metal inserts,” which was curtailed due to COVID‑19 restrictions and inter‑partner dependencies. Work packages 1.4 (specification preparation), 6.5 (component manufacturing and delivery for the demonstrator), and 9 (reporting and documentation) were completed. The project produced a final report, a technical documentation package, and a set of test results that demonstrate the feasibility of the developed surface treatments.
Schaeffler Technologies AG & Co. KG supplied metal inserts and provided the mechanical design of the demonstrator. Hexion GmbH performed adhesion testing, while TU Chemnitz conducted interface analyses. TRUMPF GmbH + Co. KG carried out laser structuring of the metal surfaces. The collaboration was coordinated by Holger Kaup of Schaeffler Technologies, who served as project coordinator. The project’s outcomes include validated phosphating recipes, a reproducible cleaning protocol, and evidence that laser‑structured, phosphated metal surfaces can achieve strong, durable bonds with duroplastic, paving the way for future high‑performance composite components.