Recent progress on polymer materials for additive manufacturing

https://onlinelibrary.wiley.com/doi/pdf/10.1002/app.48545

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

Comparison study of the ignition and combustion characteristics of directly-written Al/PVDF, Al/Viton and Al/THV composites

Silicon carbide (SiC) ceramic and related materials are widely used in various military and engineering fields. The emergence of additive manufacturing (AM) technologies provides a new approach for the fabrication of SiC ceramic products. This article systematically reviews the additive manufacturing technologies of SiC ceramic developed in recent years, including Indirect Additive Manufacturing (Indirect AM) and Direct Additive Manufacturing (Direct AM) technologies. This review also summarizes the key scientific and technological challenges for the additive manufacturing of SiC ceramic, and also forecasts its possible future opportunities. This paper aims to provide a helpful guidance for the additive manufacturing of SiC ceramic and other structural ceramics.

/pdf/progress-and-challenges-towards-additive-manufacturing-of-1xhctqjcru.pdf

Progress and challenges towards additive manufacturing of SiC ceramic

The effective solid propellant burning rate in a rocket depends on surface area and propellant composition. Currently, the surface area geometry in a rocket is limited to what can be practically cast using molds, etc. Additive manufacturing (AM) could allow the production of unique propellant grain geometries, however printing propellants with high solids loadings and viscosities is not readily possible using currently available printers. A new AM direct write system developed recently in our laboratory, is capable of printing visibly low-void propellants with high end mix viscosities into highly resolved geometries. The system was used to print ammonium perchlorate (AP) composite propellants at 85% solids loading using hydroxyl-terminated polybutadiene (HTPB) and a UV-curable polyurethane binder. The change in HTPB propellant viscosity with time after mixing was measured and the microstructure of the strands was evaluated with X-ray tomography scans. The burning rate of printed and cast strands was measured to compare the quality of the strands at high pressure, since propellants with significant voids should catastrophically fail due to flame spreading. The printed samples burned in a planar fashion up to pressures of 10.34 MPa with consistent rates that were comparable to the cast propellants. The HTPB propellant used was not optimized and showed some porosity due to gas generation, but strands printed with the UV binder exhibited extremely low porosity. A strand printed with no gaps in one half and gaps in the other failed catastrophically where intended at high pressure, demonstrating the ability to spatially grade propellants. This new system can produce adequate strands of composite propellant with high solids loadings without the addition of solvents, special binders (low viscosity, thermal softening, etc.), or restricting use to formulations with lower viscosities, and enables the fabrication of complex propellant grain geometries.

Additive manufacturing of ammonium perchlorate composite propellant with high solids loadings

Heterogeneous materials used in biomedical, structural and electronics applications contain a high fraction of solids (>60 vol.%) and exhibit extremely high viscosities (μ > 1000 Pa s), which hinders their 3D printing using existing technologies. This study shows that inducing high-amplitude ultrasonic vibrations within a nozzle imparts sufficient inertial forces to these materials to drastically reduce effective wall friction and flow stresses, enabling their 3D printing with moderate back pressures (

Monique McClain

Papers

Additive manufacturing of ammonium perchlorate composite propellant with high solids loadings

3D printing of extremely viscous materials using ultrasonic vibrations

Development and Characterization of a Photopolymeric Binder for Additively Manufactured Composite Solid Propellant Using Vibration Assisted Printing

Investigation of Additively Manufactured Layered Composite Solid Propellant

Solid Propellant with Embedded Additively Manufactured Reactive Components