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Previous work showed that thermoplastic composite sandwich structures offer great potential to meet the demands of lightweight structures for aviation applications. In this study, the influence of several processing parameters on the mechanical properties of thermoplastic sandwich components, consisting of carbon fibre reinforced polyetheretherketone skins and polyetherimide foam cores, is characterised. Sandwich specimens are manufactured with varying skin temperatures, core compaction distances and different polyetherimide concentrations at the skin–core interface. Following, sandwich samples are mechanically tested to characterise the bond strength, the core performance as well as the performance of the whole sandwich. The results show that in most cases the processing parameters significantly affect the cell structure of the sandwich core, provided that a proper fusion bond between skins and core exists. Thereby, the core performance seems to be weakened and failure predominantly occurs in the transition between affected and original cell structures.

The additive manufacturing industry shows annual growth of more than 10 %. Therefore, the requirements for produced components are increasing, especially for individual medical technology applications printed from poly(ether ether ketone) (PEEK). This paper focuses on an investigation of an uninterrupted nozzle system for printing the high‐performance thermoplastic PEEK with short fiber reinforcements. A custom‐made nozzle design with variable outlet angle is presented and the achievable fiber length distribution and fiber orientation in the printed material are investigated. The applied nozzle angles are 60 °, 90 ° and 120 °. The geometric shape of the tip of the custom‐made nozzles is comparable to that of a reference nozzle. With regard to the height profile, the inner surface is up to three times smoother. With a decreasing nozzle angle, a lower degree of fiber damage caused by deposition can be demonstrated. Thus, the process‐induced shortening of the fibers decreases. The enhanced flow profile for small angles outweighs the simultaneous disadvantageous due to friction loss, shear stress and pressure drop. A clear result for the fiber orientation cannot be deduced. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

The market segment of additive manufacturing is showing an annual growth of more than ten percent, with extrusion-based processes being the larger segment of the market. The scope of use is limited to secondary structures. Equipment manufacturers try to guarantee constant material characteristics by closed systems. The characteristic values are up to 50% below the ones from injection molding. The processing of high-performance polymers with reinforcing fibers is an additional challenge. Further development requires an opening of the material and manufacturing systems. The guidelines and standardization for this are still missing. For this reason, a functional analysis (FA) according to TRIZ ("theory of the resolution of invention-related tasks") is performed within this study. This identifies the undesired functions and quantifies their coupling with process components and parameters. In the FA, the manufactured part is the target component in order to address its quality. This way the FA identifies five undesirable functions in the process. These are: deform, cool, weaken, swell and shape. For hightemperature thermoplastics, thermal shrinkage is the primary cause of geometric tolerance. Therefore, the deformation is largely dependent on the cooling mechanism. For a detailed analysis, the polymer melt is further disassembled. The results are six sub-components. The weakening is mainly due to the physical phase of the voids, which exists during the entire processing. The breakdown comprises physical fields such as stress, temperature and flow. These determine the output properties as well as the bonding between the layers. The associated functions are the swelling and shaping. In order to generate broadly applicable standardizations, research questions for further investigation are derived from this study.

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