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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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41 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Design and Use of a Penetrating Deposition Nozzle for Z-Pinning Additive Manufacturing

Fused Filament Fabrication (FFF) involves depositing material layer-by-layer to create athree-dimensional object. This method often demonstrates high mechanical anisotropy in theprinted structure, leading to a drop in the material strength of the part when comparing structuresalong the deposition plane (X/Y-Axis) versus across layers in the build direction (Z-Axis). Initialefforts to improve anisotropy led to the development of the Z-Pinning process, where continuouspins are deposited across layers in the Z-Axis. Z-pinning has demonstrated significant gains intoughness and inter-layer strength, particularly in fiber-reinforced materials. However, thisprocess can also create flaws in the structure that increase in severity and frequency as the pinsgrow in length and diameter. To mitigate this, a penetrating nozzle has been developed thatextends a fine-tipped extrusion nozzle deep into the pin cavity and simultaneously extrudesmaterial as it retracts. This study investigates the printability of the penetrating nozzle for simplegeometries and evaluates the resulting Z-pinning mesostructure. As a result of this study, theprototype penetrating nozzle design was analyzed and built. Through a pressure driven flowanalysis it was determined that the penetrating nozzle extruder can not only flow extrudefilament. After a transient thermal simulation it was found that after a pause of 15 secondsresume printing with no drop in heat at nozzle exit.

Bales, Brenin↗
DOE OSTI2022

Metal fiber composite additive manufacturing (MFC-AM) and composite structures formed by MFC-AM

In a metal fiber composite (MFC) additive manufacturing (AM) method, a layer of polymer structures is deposited using a fused filament fabrication (FFF) printer assembly comprising at least one nozzle. Subsequently, an MFC printer assembly is used to embed a continuous metal fiber into one or more of the polymer structures of the layer. The embedding is achieved by heating the metal fiber and applying pressure to the metal fiber using an embedding surface of the MFC printer assembly. The heated metal fiber melts polymer adjacent thereto, thereby allowing the pressure to embed the metal fiber into the polymer structure. Using the MFC-AM method, various composite structures can be formed, such as novel heat exchangers that may otherwise be difficult or impossible to fabricate via other manufacturing techniques.

Hymas, David M.↗
DOE OSTI2023

Experimental and Numerical Investigations on Dynamic Mechanical Properties of TPMS Structures

Triply Periodic Minimal Surface (TPMS) lattice structures have been of increasing interest due to their light weighting, enhanced mechanical properties, and energy absorption characteristics for automotive and biomedical applications. With the advent of additive manufacturing and geometric modeling software, TPMS lattices with complex geometries can be realized. In this work, TPMS lattice structures were fabricated with PLA using fused filament fabrication (FFF) and their dynamic properties are characterized through drop tower experiments. Although lightweight TPMS lattices are beneficial for their impact absorption capability, most of the existing works are limited to quasi-static compression and dynamic impact tests are rarely performed. The current study investigates the stress-strain and energy absorption characteristics of TPMS lattices through drop tower testing and numerical modeling. Finite element modeling for TPMS lattices is carried out to validate the experimental responses. The mechanical properties, deformation, and failure mechanisms of TPMS lattices under dynamic impact are summarized for potential future applications.

Pokkalla, Deepak↗
DOE OSTI2024

Toolpath considerations for extrusion: Pellet, filament, concrete, and thermoset

There are a variety of extrusion and deposition-based processes for additive manufacturing, such as fused deposition modeling (FDM), fused filament fabrication (FFF), and directed energy deposition (DED). These processes can use a variety of materials, including thermoplastic pellets, thermoplastic filament, thermoset, concrete, metal wire, metal powder, and more. For all these processes and materials, the underlying toolpath strategies for 3D-printing an object are the same: the object to be printed is sliced into layers, then the layer is optimally fit with toolpaths of a given width, based on specific user settings. However, based on the specific process being used, additional modifiers and toolpathing strategies may be employed to maximize the capabilities of the process and successfully construct an object. This chapter explores the different pathing considerations and additional strategies to be employed in extrusion processes that use thermoplastics, thermosets, and concretes.

Roschli, Alex↗
DOE OSTI2021

Development of Antimicrobial PLA Composites for Fused Filament Fabrication

In addition to possessing the desirable properties of being a biodegradable and biocompatible polymer fabricated from renewable resources, poly (lactic acid) (PLA) has useful mechanical and thermal attributes that has enabled it to be one of the most widely-used plastics for medicine, manufacturing, and agriculture. Yet, PLA composites have not been heavily explored for use in 3D-printing applications, and the range of feasible materials for the technology is limited, which inhibits its potential growth and industry adoption. In this study, tunable, multifunctional antimicrobial PLA composite filaments for 3D-printing have been fabricated and tested via chemical, thermal, mechanical, and antimicrobial experiments. Thermally stable antimicrobial ceramics, ZnO and TiO2, were used as fillers up to 30 wt%, and poly (ethylene glycol) (PEG) was used as a plasticizer to tune the physical material properties. Results demonstrate that the PLA composite filaments exhibit the thermal phase behaviors and thermal stability suitable for 3D-printing. Additionally, PEG can be used to tune the mechanical properties while not affecting the antimicrobial efficacy that ZnO and TiO2 imbue.

TiO2↗