Abstract
The demand for additively manufactured polymer composites with increased specific properties and functional microstructure has drastically increased over the past decade. The ability to manufacture complex designs that can maximize strength while reducing weight in an automated fashion has made 3D-printed composites a popular research target in the field of engineering. However, a significant amount of understanding and basic research is still necessary to decode the fundamental process mechanisms of combining enhanced functionality and additively manufactured composites. In this review, external field-assisted additive manufacturing techniques for polymer composites are discussed with respect to (1) self-assembly into complex microstructures, (2) control of fiber orientation for improved interlayer mechanical properties, and (3) incorporation of multi-functionalities such as electrical conductivity, self-healing, sensing, and other functional capabilities. A comparison between reinforcement shapes and the type of external field used to achieve mechanical property improvements in printed composites is addressed. Research has shown the use of such materials in the production of parts exhibiting high strength-to-weight ratio for use in aerospace and automotive fields, sensors for monitoring stress and conducting electricity, and the production of flexible batteries.
Highlights
In recent years, additive manufacturing has seen a rise in the development of low-priced extrusion-based printers, for enthusiasts and designers in small office settings [1,2]
The combination of high-modulus and high strength fibers with a polymer matrix produces a composite with high stiffness, strength, and lower coefficient of thermal expansion, previous attempts to randomly introduce composites to additive manufacturing methods have raised many limitations and issues with regards to fiber size, non-uniformity, the ability of the matrix material to hold its shape after deposition, and energy absorption of metal fibers, to name a few [37,51,52,53]
Magnetic particles are typically used for prints in the millimeter to micrometer range, the Oakridge National Lab has implemented a composite material with 65 vol.% of NdFeB in Nylon-12 to manufacture large magnets using their Big Area Additive Manufacturing (BAAM) system and compared results with traditional injection-molded magnets to prove that BAAM is capable of producing a better hysteresis loop and higher intrinsic coercivity and remanence values [102]
Summary
Additive manufacturing has seen a rise in the development of low-priced extrusion-based printers, for enthusiasts and designers in small office settings [1,2]. CVD has shown to produce tailored shapes and structures such as 2D triangles, 3D pyramids, and hexagons just by varying the vertical distance between the substrate and the precursor, which is a major determining factor for the quality and microstructure of an additively manufactured part [28,29] Techniques such as aerosol jet process, and precision syringe-based nozzle dispensing processes, have the potential to be used for the production of high-resolution 3D microstructures [30]. Processes such as stereolithography (SLA), selective laser sintering (SLS), 3D printing (3DP), fused filament fabrication (FFF) and laminated object manufacturing (LOM) have been classified as a group of technologies that have the potential to efficiently fabricate intricate and complex 3D microstructures
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