Fracture mechanical characterization and lifetime estimation of near-homogeneous components produced by fused filament fabrication

Huber

et al. 2019

Macro Materials & Eng

Self Cite

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.

“…This indicates excellent inter‐ and intra‐layer bonding (Figure c), similarly to refs. . Furthermore, it affirms the assumption of an almost homogeneous material, as indicated above.…”

Section: Resultssupporting

confidence: 83%

Section: Methodsmentioning

confidence: 90%

Impact Optimization of 3D‐Printed Poly(methyl methacrylate) for Cranial Implants

Petersmann

Huber

et al. 2019

Macro Materials & Eng

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“…Concurrently, if the viscosity is high, the filament needs to reveal an improved strength and stiffness to be able to pass through the nozzle . However, high viscosities can be counteracted by increased nozzle temperatures or by implementing additional hardware like an ultrasonic transducer at the nozzle, resulting in an easier dispensability of the melt . For composites, although, highly viscous materials tend to agglomerate, which can result in clogged printing nozzles .…”

Section: Introductionmentioning

confidence: 99%

Material extrusion‐based additive manufacturing of polypropylene: A review on how to improve dimensional inaccuracy and warpage

J of Applied Polymer Sci

Holzer

González-Gutiérrez

2019

Self Cite

201

172

Material extrusion-based additive manufacturing (ME-AM) is an emerging processing technique that is characterized by the selective deposition of thermoplastic filaments in a layer-by-layer manner based on digital part models. Recently, it has attracted considerable attention, as this technique offers manifold benefits over conventional manufacturing technologies. However, to meet the challenges of complex industrial applications, certain shortcomings of ME-AM still need to be overcome. A case in point is the limited amount of semicrystalline thermoplastics, which are still not established as reliable, commercial filament materials. Particularly, polypropylene (PP) offers attractive properties that are unique among the ME-AM material portfolio. This review describes the current approaches of fabricating PP components by ME-AM. Both commercial and scientific strategies to make PP 3D-printable are elaborated and compared. As dimensional issues are especially problematic for PP, a comprehensive section of this review focuses on the strategies developed for mitigating warpage for PP parts fabricated by ME-AM.

“…The process relies on the selective deposition of thermoplastic strands according to a computer aided design (CAD)‐defined contour, in which successive layers are stacked upon each other. Therefore, a flexible filament is continuously transported by two counter‐rotating driving wheels through a liquefier and a moving nozzle until the desired part is shaped . This technique allows the rapid, flexible, and cost‐effective fabrication of diverse customized products .…”

Section: Introductionmentioning

confidence: 99%

Polypropylene Filled With Glass Spheres in Extrusion‐Based Additive Manufacturing: Effect of Filler Size and Printing Chamber Temperature

Arbeiter

Raguž

et al. 2018

Macro Materials & Eng

Self Cite

108

A challenge in extrusion‐based additive manufacturing of polypropylene (PP) filled with spherical particles is the combination of decent processability, excellent warpage control, and the retention of the tensile strength of neat PP. This study addresses this issue by adopting two approaches. Firstly, different size fractions of borosilicate glass spheres incorporated into PP are compared. Secondly, the temperature of the printing chamber (TCh) is varied. The effects of these features on the thermal, crystalline, morphological, tensile, impact, and warpage properties of 3D‐printed parts are examined. Smaller glass spheres (<12 µm) are found to be superior to larger fractions in all investigated aspects. Notably, the corresponding composites show higher tensile strengths than neat PP. An increase in TCh results in a more homogeneous temperature distribution within the printing chamber and promotes annealing during printing. Consequently, the dimensional accuracy of printed parts is improved. Additionally, β‐crystals and larger spherulites are formed at a higher TCh.