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The Arburg Plastic Freeforming process (APF) is a unique additive manufacturing material jetting method. In APF, a thermoplastic material is supplied as pellets, melted and selectively deposited as droplets, enabling the use of commercial materials in their original shape instead of filaments. The medical industry could significantly benefit from the use of additive manufacturing for the onsite fabrication of customized medical aids and therapeutic devices in a fast and economical way. In the medical field, the utilized materials need to be certified for such applications and cannot be altered in any way to make them printable, because modifications annul the certification. Therefore, it is necessary to modify the processing conditions rather than the materials for successful printing. In this research, a medical-grade poly(methyl methacrylate) was analyzed. The deposition parameters were kept constant, while the drop aspect ratio, discharge rate, melt temperatures, and build chamber temperature were varied to obtain specimens with different geometrical accuracy. Once satisfactory geometrical accuracy was obtained, tensile properties of specimens printed individually or in batches of five were tested in two different orientations. It was found that parts printed individually with an XY orientation showed the highest tensile properties; however, there is still room for improvement by optimizing the processing conditions to maximize the mechanical strength of printed specimens.

Material extrusion‐based additive manufacturing, also known as fused filament fabrication (FFF) or 3D printing facilitates the fabrication of cranial implants with different materials and complex internal structures. The impact behavior plays a key role in the designing process of cranial implants. Therefore, the performance of impact tests on novel implant materials is of utmost importance. This research focuses on investigating the dependency of the infill density and pattern on the impact properties of 3D‐printed poly(methyl methacrylate) (PMMA) sandwich specimens including internal rectilinear, gyroid, and 3D‐honeycomb (3D‐HC) structures. 3D‐HC structures show higher impact forces and dissipated energies as well as dynamic stiffness values compared to rectilinear and gyroid structures at the same infill density. 70% infill 3D‐HC and 100% infill rectilinear structures prove to be most promising. In addition, two different optimization techniques to further improve the impact properties of these specimens, namely a material and a topology optimization, are applied. Topology optimization shows promising results until first damage and material optimization regarding dissipated energies. However, both are not able to outperform the 3D‐HC pattern.

The aim of this study is to show the influence of using compliant interlayers as crack arresters for three-dimensional (3-D)-printed polymeric structures. To investigate the effectiveness of compliant interlayers, specimens consisting of a stiff and brittle matrix and thin compliant interlayers were printed. The results of these polymeric composites were compared to pure matrix material samples. To generate specimens, a commercially available material extrusion-based desktop 3-D-printer was used. Additively manufactured samples were tested in both impact as well as fracture mechanical tests. The application of a compliant interlayer as crack arrester showed high potential in both types of test. Instrumented Charpy impact tests according to EN ISO 179-2 revealed an increase of notched impact strength from 5.0 ± 0.1 kJm−2 to 25 kJm−2 (energy up to Fmax) and 136 ± 2.6 kJm−2 (total energy during testing), respectively. This indicates an increase of roughly 725% and 2,720%, while the maximum force during testing remained almost unchanged at approximately 200 N. Interestingly, the exact position as well as the number of compliant interlayers did not show a significant influence on the results. Therefore, tests that are more detailed were conducted on specimens including only a single interlayer. Further tests consisted of J-integral testing on specimens with aforementioned single compliant interlayers. Crack resistance (J-R curves) were generated using the multi-specimen approach and evaluation according to the protocol of the European Structural Integrity Society. Although a special data-shifting procedure has to be applied to interpret results more clearly, J-integral values showed a significant increase of 250 % at the interface between materials compared to the pure matrix material.