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Additive manufacturing (AM) of polymer composites with continuous fibers could play a major role in the future of aerospace and beyond but will require printed materials to achieve new levels of reliability. This study characterized the strength distribution of selected thermoplastic matrix composites as a func- tion of printing via fused filament fabrication (FFF). Experimental and commercial composite filaments of continuous carbon or Kevlar fibers were printed with volume fraction (Vf) ranging from approximately 28 to 56 %. The strength was evaluated under uniaxial tension after specific stages of printing and Weibull statistics were applied to characterize the strength distribution. There was a significant reduction in strength of the printed material with respect to the unprinted condition, regardless of reinforcement type, fiber volume fraction or printer used. Damage introduced by feed extrusion of the filament, and fiber failures induced at material deposition were most detrimental. For carbon fiber filaments, the reduc- tion ranged from approximately 10 % for an experimental material to over 60 % for a commercial filament. There was no correlation in the strength degradation or variability with Vf. The prevention of process-related fiber damage is key to advancing AM for continuous fiber composite and application to designs intended for stress-critical applications.
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Continuous multi-filament 3D printing for tension-compression structure components
In this research, we propose a Multi-Filament Fused Deposit Modelling (MFFMD) printer and a respective generator that can be used to produce structural parts with locally tailored functional properties. 3D-printed structural components can highly benefit from multi-material printing with tuneable functional properties. Currently, multi-material printing is mainly achieved using multiple separate nozzles, leading to discontinuous flow in switching materials. This limitation results in material interface delamination, minimal control in the continuous transition of material properties, and longer production time.To address this, we first design and build an MFFMD printer with a single customized nozzle allowing seamless switching between multiple filaments. We then develop a method that generates a continuous toolpath of a given geometry and differentiates materials based on various stress conditions at particular regions. To illustrate, we fabricate a Pratt truss as an example of a tension-compression structure as a case study. In one go, the MFFMD printer deposits resistant filament, respectively, at tension- or compression-concentrated regions based on local stress conditions. Comparative load tests are conducted to validate the performance enhancement of multi-filament prints against single-filament prints. Our proposed method is a prototypical study conducted on a small scale. While it mainly uses thermal plastic filaments, it can be expanded to other construction materials and scales in the future.
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- Award ID(s):
- 2037097
- PAR ID:
- 10465100
- Date Published:
- Journal Name:
- Proceedings of the IASS Annual Symposium 2023
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Commercially available fused deposition modeling (FDM) printers have yet to bridge the gap between printing soft, flexible materials and printing hard, rigid materials. This work presents a custom printer solution, based on open-source hardware and software, which allows a user to print both flexible and rigid polymer materials. The materials printed include NinjaFlex, SemiFlex, acrylonitrile-butadiene-styrene (ABS), Nylon, and Polycarbonate. In order to print rigid materials, a custom, high-temperature heated bed was designed to act as a print stage. Additionally, high temperature extruders were included in the design to accommodate the printing requirements of both flexible and rigid filaments. Across 25 equally spaced points on the print plate, the maximum temperature difference between any two points on the heated bed was found to be ∼9°C for a target temperature of 170°C. With a uniform temperature profile across the plate, functional prints were achieved in each material. The print quality varied, dependent on material; however, the standard deviation of layer thicknesses and size measurements of the parts were comparable to those produced on a Zortrax M200 printer. After calibration and further process development, the custom printer will be integrated into the NEXUS system — a multiscale additive manufacturing instrument with integrated 3D printing and robotic assembly (NSF Award #1828355).more » « less
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Abstract Among the wide range of additive manufacturing — or “three-dimensional (3D) printing” — technologies, “material jetting” approaches are distinctively suited for multi-material fabrication. Because material jetting strategies, such as “PolyJet 3D printing”, harness inkjets that allow for multiple photopolymer droplets (and sacrificial support materials) to be dispensed in parallel to build 3D objects, distinct materials with unique properties can be readily unified in a single print akin to combining multiple-colored inks using a conventional 2D color printer. Although researchers have leveraged this multi-material capability to achieve, for example, 3D functionally graded and bi-material composite systems, there are cases in which the interface between distinct materials can become a key region of mechanical failure if not designed properly. To elucidate potential design factors that contribute to such failure modes, here we investigate the relationship between the interface design and tensile mechanical failure dynamics for PolyJet-printed bi-material coupons. Experimental results for a select set of bi-material sample designs that were 3D printed using a Stratasys Objet500 Connex3 PolyJet 3D printer and subjected to uniaxial tensile testing using a Tinius Olsen H25K-T benchtop universal testing machine under uniaxial strain revealed that increasing the surface contact area between two distinct materials via changes in geometric design does not necessarily increase the interface strength based on the length scales and loading conditions investigated in the current study and that further studies of the role of multi-material geometric designs in interface integrity are warranted to understand potential mechanisms underlying these results. Given the increasing interest in material jetting — and PolyJet 3D printing in particular — as a pathway to multi-material manufacturing in fields including robotics and fluidic circuitry, this study suggests that multi-material interface geometry should be considered appropriately for future applications.more » « less
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Eds: Babski-Reeves, K; Eksioglu, B; Hampton, D. (Ed.)The emerging field of three-dimensional bio-printing seeks to recreate functional tissues for medical and pharmaceutical purposes. With the ability to print diverse materials containing different living cells, this growing area may bring us closer to achieving tissue regeneration. In previous research, we developed a Y-shaped nozzle connection device that facilitated the continuous deposition of materials across multiple filaments. This plastic device had a fixed switching angle and was intended for single use. In this study, we present an extension of our previous nozzle system. To fabricate the nozzle connectors, we chose stainless steel and considered angles of 300, 450, and 900 (both vertical and tilted) between the two materials. The total material switching time was recorded and compared to analyze the effects of these angles. We used our previously developed hybrid hydrogel (4% Alginate and 4% Carboxymethyl Cellulose, CMC) as a test material to flow through the nozzle system. These in-house fabricated nozzle connectors are reusable, and sterile and enable smooth material transition and flow.more » « less
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Abstract Three-dimensional (3D) bio-printing is a rapidly growing field attempting to recreate functional tissues for medical and pharmaceutical purposes. The printability of multiple materials encapsulating various living cells can take this emerging effort closer to tissue regeneration. In our earlier research, we designed a Y-like nozzle connector system capable of switching materials between more than one filament with continuous deposition. The device had a fixed switching angle, was made from plastic, and was suitable for one-time use. This paper presents the extension of our previously proposed nozzle system. We considered 30°, 45°, 60°, and 90° angles (vertical and tilted) between the two materials and chose stainless steel as a material to fabricate those nozzle connectors. The overall material switching time was recorded and compared to analyze the effects of those various angles. Our previously developed hybrid hydrogel (4% Alginate and 4% Carboxymethyl Cellulose, CMC) was used as a test material to flow through the nozzle system. These in-house fabricated nozzle connectors are reusable, easy to clean, and sterile, allowing smooth material transition and flow.more » « less
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