Additive manufacturing of high-performance polymers—such as PA12, PPS, PEEK, and PEKK—combined with industrial-grade carbon fibers with a high fiber volume ratio of up to 60% allows a weight reduction of over 40% compared to classic metal construction. Typically, these 3D-printed composites have a porosity of 10–30% depending on the material and the printing process parameters, which significantly reduces the quality of the part. Therefore, the additive manufacturing of load-bearing structural applications requires a proper consolidation after the printing process—the so-called ‘additive fusion technology’—allowing close to zero void content in the consolidated part. By means of the upfront digital modeling of the consolidation process, a highly optimized composite component can be produced while decreasing the number of expensive prototyping iterations. In this study, advanced numerical methods are presented to describe the consolidation process of additive manufactured continuous carbon fiber reinforced composite parts based on the polyamide 12 (PA12) matrix. The simulation of the additive fusion step/consolidation provides immediate accuracy in determining the final degree of crystallization, process-induced deformation and residual stresses, final engineering constants, as well as porosity. The developed simulation workflow is demonstrated and validated with experimental data from consolidation tests on the final porosity, thickness, and fiber–volume ratio.

This paper describes the application of poly(ether-block-amide) polymers, so-called Pebax, in fused filament fabrication (FFF). Pebax® is a thermoplastic elastomer (TPE), a copolymer based on rigid polyamide and soft polyether blocks. By variation of the blocks, unique properties such as soft or rigid behaviour are tailored without additional additives and plasticisers. Pebax®Rnew® polyamide blocks are bio-based and made from castor beans that allow the design of sustainable applications. In this study, two types of Pebax were selected, processing parameters were characterised, filaments were extruded and applied to FFF printing, and the final mechanical characteristics were determined. Both types were suitable for FFF processing with improved process stability due to less shear thinning and good mechanical performance. The connection strength between the grades was also described in the design context for complex parts with tailored soft or hard regions. Combining the two materials in one design is a promising concept, and the adhesion strength is close to the strength in the Z-direction of the flexible Pebax®Rnew®35R53 grade.

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Substitution of conventional metal structures with fiber-reinforced polymers is possible because of their sustainable performance. One of the primary disadvantages of these composite materials is their high cost due to labor-intensive manufacturing. Because the fiber path can be steered directly along the load path, structures can be manufactured in a near-net shape, and a high degree of reproducibility with low scrap rates can be achieved. Additive manufacturing of these composite structures could enable cost efficiency with a high degree of complexity. However, the high degree of porosity and high void content between the printed fiber filaments results in unacceptable structural performance. Following the printing process, a post-consolidation process (additive fusion) can be performed to improve the mechanical performance of the part and use fiber-reinforced polymers for load-bearing applications. Numerical simulation of the consolidation process enables the production of these complex parts without expensive prototyping iterations. Because of the rapid and local changes in material stiffness, the simulation of the consolidation process is combined with a set of numerical model convergence problems. An advanced finite-element numerical model for simulating the consolidation process of additive manufactured continuous fiber composite parts is presented in this paper. The additive fusion step simulation allows for the evaluation of process-induced deformations, final engineering constants, and porosity. The simulation workflow is demonstrated and validated using experimental data from the manufacturing process of a typical aerospace part, specifically a helicopter hinge element.

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