Influence of Transfer Film Formation Mechanisms on the Friction and Wear of Polymer Matrix Composites

• Applicant: Dr.-Ing. Bernd Wetzel
• Subject Area: Polymeric and Biogenic Materials and Derived Composites
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389811744

Previous studies performed during the last two years revealed the capability of silica nanoparticles towards forming a wear-resistant film at a specific pv-load range which overcomes the unacceptable macroscopic wear of the conventional composite without nanofiller. Furthermore, it was observed that a certain roughness of the counterbody and minimum pv-load is essential for obtaining well adhering transfer films of the desired structure and properties. These well adhering transfer films are made of almost exclusively nanofillers.Our hypothesis is that filler size and counterbody roughness should be of the similar magnitude in order to obtain optimum conditions for in situ generating protecting films. If this consideration is right, an optimum surface topography applies for each filler size. Furthermore, by applying higher loads in the running-in regime, it is possible to generate protecting films that can be used in lower loads afterwards. Finally, due to the fact that almost no matrix material is in transfer film, the formation mechanisms of this well adhering transfer film might be transferable to other polymers. The main goal of the new proposal is to prove these hypotheses by experimental and numerical approaches while also fundamentally investigating transfer film properties such as film thickness and distribution.For the experimental approach, silica particles in the size range 50, 250, and 1000 nm will be synthesized and used in polymer composites, while appropriate surface structuring will be performed by laser treatment. Multimodal particle size distribution will be considered as well, e.g. the combination of 50 nm and 250 nm sized particles in one specific composite. Target is to derive influences of particle size and surface topography on the formation mechanisms of the resultant transfer films. In the second series of tests, the influence of the load history test under both increasing and decreasing pv-loads are conducted. The objective is to utilize the results to create well adhering transfer films in the running-in regime, and for lower loads in the steady-state regime afterwards. Finally, by replacing the epoxy matrix for a thermoplastic matrix, the transferability of the so far identified transfer film formation mechanisms is investigated. The results will have a major impact on customizing well defined tribological properties according to demands.Tribofilm formation modelling will be performed by the movable cellular automata method. The automata size will be varied in the same range as the silica particle size (50 to 1000 nm, multimodal). Loads and the roughness of the counterpart surface will be adjusted accordingly.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research
• Co-Investigator: Professor Dr.-Ing. Klaus Friedrich (†)
• Cooperation Partner: Professor Andrey I. Dmitriev, Ph.D.