Nano-reinforcements in carbon fibre-reinforced polymer (CFRP) have proven to enhance the mechanical properties considering quasi-static, as well as fatigue load and, are a promising option with regard to CFRP performance optimisation. While general knowledge about the nanofiller content and its influence in CFRP is well documented, the use of alignment techniques for a specific orientation of the nano-reinforcements is still insufficiently studied. In this work, the influence of oriented carbon nanofibres (CNF) on the mechanical properties of bidirectional CFRP is investigated. CFRP was produced CNF-reinforced with and without orientation using a hot press, where an electric field was applied during curing. The laminates were characterised with respect to dispersion quality, pore volume, quasi-static properties (tensile and bending tests) and dynamic properties (fatigue tests). Electrical resistance measurement was applied together with digital image correlation and in situ computed tomography to generate knowledge about the fatigue-related damage evolution and evaluate the sensors for viable use of condition monitoring. Results show that the orientation of CNF has a significant impact on both quasi-static and fatigue properties, increasing the strength while reducing and slowing down the introduced damage. Orientation of nanofillers thus shows large optimization potential of mechanical properties of CFRP components.

The knowledge of alloy–process–structure–property relationships is of particular interest for several safety-critical brazed components and requires a detailed characterization. Thus, three different nickel-based brazing filler metals were produced with varying chromium and molybdenum content and were used to braze butt joints of the austenitic stainless steel AISI 304L under vacuum. Two holding times were used to evaluate diffusion-related differences, resulting in six specimen variations. Significant microstructural changes due to the formation and location of borides and silicides were demonstrated. Using X-ray diffraction, alloy-dependent residual stress gradients from the brazing seam to the base material were determined and the thermal-induced residual stresses were shown through simulations. For mechanical characterization, impact tests were carried out to determine the impact toughness, as well as tensile tests at low and high strain rates to evaluate the strain-rate-dependent tensile strength of the brazed joints. Further thermal, electrical, and magnetic measurements enabled an understanding of the deformation mechanisms. The negative influence of brittle phases in the seam center could be quantified and showed the most significant effects under impact loading. Fractographic investigations subsequently enabled an enhanced understanding of the fracture mechanisms.

Additive manufacturing techniques enable the fabrication of new lightweight components with tailored mechanical properties. Considering current application fields, components are often over-dimensioned since a lack of data regarding the mechanical properties under compression or tensile loading at high strain rates is present. In this work, the influence of various strain rates on the mechanical properties of electron beam powder bed fusion Ti6Al4V lattice structures was investigated. In order to capture the damage mechanisms that occurred, a single unit cell plane was considered. In terms of mechanical characterization, high-speed tensile tests at nominal strain rates from 0.025 to 250 s-1 were carried out. By the additional use of a high-speed camera system and subsequent digital image correlation, an investigation of material reactions during shortest test times was enabled. Based on the results, a positive strain rate dependency was identified for yield and ultimate tensile strength for both investigated lattice types. In detail, an increase in ultimate tensile strength of 16 % for BCC- and 20 % for F2CCZ-specimens could be detected.

Laser cutting of carbon fibre-reinforced plastics (CFRP) is a promising alternative to traditional manufacturing methods due to its non-contact nature and high automation potential. To establish the process for an industrial application, it is necessary to predict the temperature fields arising as a result of the laser energy input. Elevated temperatures during the cutting process can lead to damage in the composite’s matrix material, resulting in local changes in the structural properties and reduced material strength. To address this, a three-dimensional finite element model is developed to predict the temporal and spatial temperature evolution during laser cutting. Experimental values are compared with simulated temperatures, and the cutting kerf geometry is examined. Experiments are conducted at 45° and 90° cutting angles relative to the main fibre orientation using a 1.1 mm thick epoxy-based laminate. The simulation accurately captures the overall temperature field expansion caused by multiple laser beam passes over the workpiece. The influence of fibre orientation is evident, with deviations in specific temperature data indicating differences between the estimated and real material properties. The model tends to overestimate the ablation rate in the kerf geometry, attributed to mesh resolution limitations. Within the parameters investigated, hardly any expansion of a heat affected zone (HAZ) is visible, which is confirmed by the simulation results.

Additive manufacturing of polymers via material extrusion and its future applications are gaining interest. Supporting the evolution from prototype to serial applications, additional testing conditions are needed. The additively manufactured and anisotropic polymers often show a weak point in the interlayer contact area in the manufacturing direction. Different process parameters, such as layer height, play a key role for generating the interlayer contact area. Since the manufacturing productivity depends on the layer height as well, a special focus is placed on this process parameter. A small layer height has the objective of achieving better material performance, whereas a larger layer height is characterized by better economy. Therefore, the capability- and economy-oriented variation was investigated for strain rates between 2.5 and 250 s⁻¹ under tensile and shear load conditions. The test series with dynamic loadings were designed monitoring future applications. The interlayer tensile tests were performed with a special specimen geometry, which enables a correction of the force measurement. By using a small specimen geometry with a force measurement directly on the specimen, the influence of travelling stress waves, which occur due to the impact at high strain rates, is reduced. The interlayer tensile tests indicate a strain rate dependency of additively manufactured polymers. The capability-oriented variation achieves a higher ultimate tensile and shear strength compared to the economy-oriented variation. The external and internal quality assessment indicates an increasing primary surface profile and void volume content for increasing the layer height.