Fiber‐filled composite materials offer a unique pathway to enable new functionalities for systems built via extrusion‐based additive manufacturing (or “3D printing”); however, challenges remain in controlling the fiber orientations that govern ultimate performance. In this work, a multi‐material, shape‐changing nozzle—constructed by means of PolyJet 3D printing—is presented that allows for the spatial distribution of short fibers embedded in polymer matrices to be modulated on demand throughout extrusion‐based deposition processes. Specifically, the nozzle comprises flexible bladders that can be inflated pneumatically to alter the geometry of the material extrusion channel from a straight to a converging–diverging configuration, and in turn, the directional orientation of fibers within printed filaments. Experimental results for printing carbon microfiber‐hydrogel composites reveal that increasing the nozzle actuation pressure from 0 to 100 kPa reduced the proportion of aligned fibers, and notably, prompted a transition from anisotropic to isotropic water‐induced swelling properties (i.e., the ratio of transverse to longitudinal swelling strain decreased from 1.73
Composites play progressively significant roles across a spectrum of applications involving high‐performance materials and products within industries such as aerospace, naval, automotive, construction, missiles, and defense technology. Notably, oriented fiber composites have garnered substantial attention due to their advantageous attributes like a high strength‐to‐weight ratio and controlled anisotropy. Nonetheless, challenges persist in uneven fiber alignment, fiber clustering within the matrix material, and constraints on fiber volume, impeding the mass production of oriented fiber‐reinforced composites. In this study, we present a novel approach to 3D printing of uniformly aligned short fiber reinforcement in a composite of heavily loaded carbon and nylon. Capitalizing on the additive manufacturing potential of rapidity and precision, the extrusion process induces carbon fiber (CF) alignments in filaments via shear forces. The 3D‐printed structures that were created displayed impressive potential for customization. They consistently demonstrated improved mechanical and thermal properties when compared to the original nylon structures. Our methodology for producing uniformly dispersed and aligned short fiber reinforcement in polymer composites promises to propel the advancement of design and manufacturing for high‐performance composite materials and components.
more » « less- Award ID(s):
- 2409815
- NSF-PAR ID:
- 10479569
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science
- ISSN:
- 2642-4150
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract ± 0.37 to 0.93± 0.39, respectively). In addition, dynamically varying the nozzle geometry during the extrusion of continuous composite filaments effects distinct swelling behaviors in adjacent regions, suggesting potential utility of the presented approach for emerging “4D printing” applications. -
null (Ed.)Abstract Pellet-based extrusion deposition of carbon fiber-reinforced composites at high material deposition rates has recently gained much attention due to its applications in large-scale additive manufacturing. The mechanical and physical properties of large-volume components largely depend on their reinforcing fiber length. However, very few studies have been done thus far to have a direct comparison of additively fabricated composites reinforced with different carbon fiber lengths. In this study, a new additive manufacturing (AM) approach to fabricate long fiber-reinforced polymer (LFRP) was first proposed. A pellet-based extrusion deposition method was implemented, which directly used thermoplastic pellets and continuous fiber tows as feedstock materials. Discontinuous long carbon fibers, with an average fiber length of 20.1 mm, were successfully incorporated into printed LFRP samples. The printed LFRP samples were compared with short fiber-reinforced polymer (SFRP) and continuous fiber-reinforced polymer (CFRP) counterparts through mechanical tests and microstructural analyses. The carbon fiber dispersion, distribution of carbon fiber length and orientation, and fiber wetting were studied. As expected, a steady increase in flexural strength was observed with increasing fiber length. The carbon fibers were highly oriented along the printing direction. A more uniformly distributed discontinuous fiber reinforcement was found within printed SFRP and LFRP samples. Due to decreased fiber impregnation time and lowered impregnation rate, the printed CFRP samples showed a lower degree of impregnation and worse fiber wetting conditions. The feasibility of the proposed AM methods was further demonstrated by fabricating large-volume components with complex geometries.more » « less
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