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5 3 I H I G H L I G H T S 2 0 2 5

PRINCIPAL PUBLICATION

Towards in situ and real time characterization of flow-induced phenomena during material extrusion of polymer composites using 3D X-ray microtomography, A.D. Betené Omgba et al., Addit. Manuf. 100, 104683 (2025); https:/doi.org/10.1016/j.addma.2025.104683

Fig. 40: a) Evolution of the mean pore volume fraction across different zones (Z2-Cr, Z2-Co, Z3-Cr, Z3-Co, Z3-Ch). b) Evolution of mean glass fibre length measured across seven distinctive nozzle zones with various output channel diameters (d = 0.4 mm and d = 0.6 mm). c) 3D images of the pore phase developing in zones Z2 and Z3 of a nozzle with an 0.4 mm-diameter output channel, along with corresponding 3D images of the fibre phase showing strong fibre alignment in the output channel

The experiment

In situ interrupted printing experiments, coupled with 3D X-ray microtomography imaging, were carried out at the BM05 beamline using a specifically designed FFF device (Figure 39) and glass-fibre-reinforced polyamide (GF30-PA6). Nozzles of various output diameters, channel lengths, and convergent angles were tested. In addition, in situ and real-time X-ray microtomography experiments were conducted at the ID19 beamline using glass-fibre polycarbonate (GF30-PC).

These experiments revealed pronounced microstructural evolution within the nozzle. Observations included pore formation linked to the deconsolidation of the molten filament, as well as pore transport and subsequent disappearance through the convergent region – attributed to the dissolution of pore gases within the polymer matrix

(Figures 40a and 40c). Furthermore, significant fibre shortening was observed (Figure 40b), along with lower-than-expected fibre alignment in the extruded filaments and fibre accumulation near the convergent zone (Figure 40c), which can contribute to nozzle clogging. The results also demonstrate the impact of nozzle geometry (e.g., convergent angle and output channel) on these mechanisms. Three-dimensional images acquired during dynamic printing experiments corroborated the findings from interrupted tests, highlighting the complex pore dynamics within the nozzle cavity and the processes that cause them to disappear through the convergent channel.

The findings provide a critical foundation for the rational design of optimised, next-generation extrusion nozzles, enabling greater control over microstructural evolution and improving the quality and consistency of polymer composite additive manufacturing.