Geförderte OA-Publikationen

In this study, different disc brakes and friction materials are evaluated with respect to particle emission output and characteristic features are derived. The measurements take place on an inertia dynamometer using a constant volume sampling system. Brake wear particle emission factors of different disc concepts in different sizes are determined and compared, using a grey cast iron disc, a tungsten carbide-coated disc and a carbon ceramic disc. The brakes were tested over a section (trip #10) novel test cycle developed from the database of the worldwide harmonized Light-Duty vehicles Test Procedure (WLTP). First, brake emission factors were determined along the bedding process using a series of trip-10 tests. The tests were performed starting from unconditioned pads, to characterize the evolution of emissions until their stabilization. In addition to number- and mass-related emission factors (PM2.5-PM10), the particle size distribution was determined. Another focus was the evaluation of temperature ranges and the associated challenges in the use of temperature readings in a potential regulation of brake wear particle emissions. The results illustrate the challenges associated with establishing a universal bedding procedure and using disc temperature measurements for the control of a representative braking procedure. Using tungsten carbide coated discs and carbon ceramic discs, emission reduction potentials of up to 70% (PM10) could be demonstrated along the WLTP brake cycle. The reduction potential is primarily the result of the high wear resistance of the disc, but is additionally influenced by the pad composition and the temperature in the friction contact area.

Hierarchical assembly architectures of functional polymer particles are promising because of their physicochemical and surface properties for multi-labeling and sensing to catalysis and biomedical applications. While polymer nanoparticles' interior is mainly made up of the cross-linked network, their surface can be tailored with soft, flexible, and responsive molecules and macromolecules as potential support for the controlled particulate assemblies. Molecular surfactants and polyelectrolytes as interfacial agents improve the stability of the nanoparticles whereas swellable and soft shell-like cross-linked polymeric layer at the interface can significantly enhance the uptake of guest nano-constituents during assemblies. Besides, layer-by-layer surface-functionalization holds the ability to provide a high variability in assembly architectures of different interfacial properties. Considering these aspects, various assembly architectures of polymer nanoparticles of tunable size, shapes, morphology, and tailored interfaces together with controllable interfacial interactions are constructed here. The microfluidic-mediated platform has been used for the synthesis of constituents polymer nanoparticles of various structural and interfacial properties, and their assemblies are conducted in batch or flow conditions. The assemblies presented in this progress report is divided into three main categories: cross-linked polymeric network's fusion-based self-assembly, electrostatic-driven assemblies, and assembly formed by encapsulating smaller nanoparticles into larger microparticles.

This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material.