Mechanical anisotropy in polymer composites produced by material extrusion additive manufacturing

Hmeidat, Nadim S.; Pack, Robert C.; Talley, Samantha J.; Moore, Robert B.; Compton, Brett G.

doi:10.1016/j.addma.2020.101385

Cited by 50 publications

(35 citation statements)

References 45 publications

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“…Aiming to achieve the stiffest shell and lowest‐density core possible utilizing the chosen ink constituents, both shell and core inks were formulated (Table S1, Supporting Information) to attain the highest practical volume loading of CF or GMB while still resulting in consistent extrusion and printing. 18 vol% CF loading in epoxy is comparable to, or higher than most examples of 3D‐printed epoxy composites in the literature, [ 11,21–24,31 ] with the notable exception of Nawafleh and Celik, [ 32 ] who achieved up to 46 vol% CF in printed epoxy composites by utilizing a novel vibration‐assisted print head. Rheological behavior (Figure S1, Supporting Information) reveals both inks display prominent shear thinning and similar viscosities of ≈10 3 Pa∙s at a 1 s −1 shear rate.…”

Section: Figurementioning

confidence: 63%

“…[11,22] An epoxy resin (Epon 826), latent curing agent, diluent, nanoclay, and CFs (18% by volume, 6 mm initial length) were utilized. While nanoclay has been shown to increase the strength and stiffness of printed epoxy composites, [9,21] it primarily serves as the rheological modifier, imparting the shear thinning and yield stress behavior required for DIW printing. Additionally, a diluent reduces initial viscosity in the epoxy resin allowing higher solids loading and a latent curing agent provides an extended printing window.…”

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confidence: 99%

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Carbon Fiber and Syntactic Foam Hybrid Materials via Core–Shell Material Extrusion Additive Manufacturing

Pack

Romberg

Badran

et al. 2020

Adv Materials Technologies

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alone, [4] thereby enabling significantly higher bending stiffness and buckling resistance in the natural hybrid architecture, and enabling optimal structural and functional performance to the organism at minimal metabolic cost. Additive manufacturing, which offers novel capabilities absent in traditional manufacturing, [7] enables fabrication of bioinspired architectures such as the C-S motif described above. In particular, direct ink writing (DIW), a type of material extrusion additive manufacturing, allows precise patterning of viscoelastic feedstock materials at ambient temperatures to build structural and/or functional components in a layer-by-layer fashion. [8] A wide variety of feedstock inks have been formulated for DIW, allowing fabrication of a broad range of materials including polymers, [9-12] ceramics, [13-15] metals, [16-18] and composites. For example, epoxy-based composite feedstocks reinforced with silicon carbide whiskers, [19-21] nanoclay, [9] graphene, [12] and carbon fibers (CFs) [11,22-24] have been explored recently to improve strength and stiffness in printed materials. Further mechanical improvement can be realized by applying the C-S architecture to high stiffness CF inks coupled with low-density foam inks for the shell and core materials, respectively. Here, we report for the first time a new C-S printhead (Figure 1b) specifically designed to print highly loaded, fiberfilled inks, as well as a new low-density syntactic epoxy foam ink for use as a low-density core material in hybrid C-S architectures. Composite-foam C-S architectures exhibit up to 25% higher specific flexural stiffness (E 1/3 /ρ) than either of the constituents alone, while the printable foam is ≈40% less dense than the existing printed polymers with comparable mechanical properties. Implementation of the C-S architecture via DIW has been investigated for both functional and structural applications with polymers and other material systems. For example, Moon et al. fabricated hollow-core ceramics by extruding a fugitive camphene core surrounded by a camphene/alumina shell, followed by sintering to densify the alumina framework. [25] Fu et al. printed carbon core-alumina shell filaments in a truss structure utilizing a piston-driven co-extrusion unit with alumina-and carbon-filled aqueous colloidal gels. [26] For lightweight hierarchical ceramic architectures, Muth et al. printed hollow C-S struts using an aqueous particle-stabilized foam Biological materials often employ hybrid architectures, such as the core-shell (C-S) motif present in porcupine quills and plant stems, to achieve unique specific properties and performance. Drawing inspiration from these natural materials, a new method to fabricate lightweight and stiff C-S architected filaments is reported. Specifically, a C-S printhead conducive to printing highly loaded fiber-filled inks, as well as a new low-density syntactic foam ink, are utilized to 3D-print C-S architectures consisting of a syntactic epoxy foam core surrounded by a stiff carbon fiber-reinforced ep...

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Section: Figurementioning

confidence: 63%

mentioning

confidence: 99%

Carbon Fiber and Syntactic Foam Hybrid Materials via Core–Shell Material Extrusion Additive Manufacturing

Pack

Romberg

Badran

et al. 2020

Adv Materials Technologies

Self Cite

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“…Many works show evidence of the preferential alignment of the fibers because of shear and extensional flow developing within the nozzle during extrusion [ 30 , 31 , 32 ]. As a consequence, Equation (2) is quite conservative since it considers that the fibers will pass through the nozzle perpendicular to the flow direction.…”

Section: Resultsmentioning

confidence: 99%

“…As a consequence, to prevent the clogging of the nozzle in this study, the maximum fiber length value is 160 µm with a nozzle diameter of 1 mm. Many works show evidence of the preferential alignment of the fibers because of shear and extensional flow developing within the nozzle during extrusion [30][31][32]. As a consequence, equation 2 is quite conservative since it considers that the fibers will pass through the nozzle perpendicular to the flow direction.…”

Section: Uv-ldm and Glass Fibers Requirementsmentioning

confidence: 99%

Additive Re-Manufacturing of Mechanically Recycled End-of-Life Glass Fiber-Reinforced Polymers for Value-Added Circular Design

et al. 2020

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Despite the large use of composites for industrial applications, their end-of-life management is still an open issue for manufacturing, especially in the wind energy sector. Additive manufacturing technology has been emerging as a solution, enhancing circular economy models, and using recycled composites for glass fiber-reinforced polymers is spreading as a new additive manufacturing trend. Nevertheless, their mechanical properties are still not comparable to pristine materials. The purpose of this paper is to examine the additive re-manufacturing of end-of-life glass fiber composites with mechanical performances that are comparable to virgin glass fiber-reinforced materials. Through a systematic characterization of the recyclate, requirements of the filler for the liquid deposition modeling process were identified. Printability and material surface quality of different formulations were analyzed using a low-cost modified 3D printer. Two hypothetical design concepts were also manufactured to validate the field of application. Furthermore, an understanding of the mechanical behavior was accomplished by means of tensile tests, and the results were compared with a benchmark formulation with virgin glass fibers. Mechanically recycled glass fibers show the capability to substitute pristine fillers, unlocking their use for new fields of application.

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“…Anisotropy of the printed material can be expected for all AM technologies [ 163 , 164 , 165 , 166 ]. Anisotropy limits the engineering applications of AM manufactured parts.…”

Section: Reinforcements In 3d Printed Partsmentioning

confidence: 99%

An Overview of Additive Manufacturing of Polymers and Associated Composites

2020

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Additive manufacturing is rapidly evolving and opening new possibilities for many industries. This article gives an overview of the current status of additive manufacturing with polymers and polymer composites. Various types of reinforcements in polymers and architectured cellular material printing including the auxetic metamaterials and the triply periodic minimal surface structures are discussed. Finally, applications, current challenges, and future directions are highlighted here.

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Mechanical anisotropy in polymer composites produced by material extrusion additive manufacturing

Cited by 50 publications

References 45 publications

Carbon Fiber and Syntactic Foam Hybrid Materials via Core–Shell Material Extrusion Additive Manufacturing

Carbon Fiber and Syntactic Foam Hybrid Materials via Core–Shell Material Extrusion Additive Manufacturing

Additive Re-Manufacturing of Mechanically Recycled End-of-Life Glass Fiber-Reinforced Polymers for Value-Added Circular Design

An Overview of Additive Manufacturing of Polymers and Associated Composites

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