High-Performance Polyamide/Carbon Fiber Composites for Fused Filament Fabrication: Mechanical and Functional Performances Sithiprumnea Dul, Luca Fambri, and Alessandro Pegoretti Submitted: 17 December 2020 / Revised: 22 February 2021 / Accepted: 27 February 2021 / Published online: 19 April 2021 This study is focused on the 3D printing by fused filament fabrication (FFF) process of short carbon-fiber- reinforced polyamide (PA) composites. In particular, the effect of short carbon fiber (CF) on the mechanical, electrical and piezoresistivity properties of 3D-printed polyamide (PA) composite parts has been analyzed. In comparison with neat PA, the results revealed that the carbon fibers effectively improved all assessed mechanical properties of PA/CF composites. In particular, in XY build orientation, PA/CF 3D- printed composites exhibited a tensile strength of 96 MPa and a tensile modulus of 7.9 GPa, with an increment of + 34 and + 147%, respectively, when compared to the neat PA. Interlayer strength of 3D- printed PA and PA/CF composites reaches similar values, in the range 26-28 MPa. The impact strength of 3D-printed XY parts was reduced by the presence of CF. However, the fracture toughness of PA/CF composite 3D-printed parts was slightly higher in comparison with that of neat PA. Electrical resistivity of PA/CF 3D-printed parts is gradually decreasing from 1.7 3 10 4 to 0.7 3 10 4 X cm in the temperature range from 2 16 to 100 °C. The piezoresistivity tests revealed that an exponential resistance change occurs for both compression-molded and 3D-printed PA/CF samples once strained in tension. A gauge factor of 3D-printed parts of about 65 ± 5 was determined from cyclic strains in the elastic region. Keywords additive manufacturing, carbon fiber-reinforced composites, high-temperature composites, mechanical properties, piezoresistivity, polyamide 1. Introduction Additive manufacturing (AM), also known as 3D printing, is a technology to build objects layer by layer based on computer- aided design (CAD). In the fabrication process of a 3D object, successive layers are laid down starting from various forms of liquid, powder or sheet materials by using an AM machine. This technology has several benefits such as the possibility to fabricate a final part without using auxiliary tool/molds and offering solutions for the manufacturing of parts that are difficult to be produced by conventional methods. It also exhibits clear advantages over removal or subtractive manu- facturing methodologies because no waste material is gener- ated. Additive manufacturing is more suitable for customized products and prototypes, but also for relatively low-volume end-use productions. According to ASTM Committee F42 (Ref 1) on additive manufacturing technologies, all additive manufacturing tech- niques can be classified into seven categories: materials extrusion, powder bed fusion, vat photopolymerization, binder jetting, materials jetting, sheet lamination and directed energy deposition. Fused filament fabrication (FFF) is a technique in the subgroup of materials extrusion, which is among the leading 3D-printing methods. In this process, a thermoplastic- based filament is extruded at a temperature above its glass transition (by about 100-150 °C) or melting (by about 20- 30 °C) temperatures through a nozzle and deposited layer by layer on a platform to build a 3D object. The FFF process is characterized by various parameters which can influence the quality of the 3D-printed components such as build orientation, layer height, infill pattern and density, printing temperature (at nozzle, bed and printing environment) (Ref 2-4). Since 3D printing leads to non-isotropic parts, the build orientation is a critical parameter. The mechanical and functional properties of thermoplastic composite materials can be targeted in view of specific applications. In general, fiber-reinforced (e.g., glass fiber, carbon fiber) composites have remarkable mechanical proper- ties, leading to successful uses in various applications (Ref 5). In the meantime, 3D printing of fiber-reinforced composites is a new field in additive manufacturing. The mechanical properties of 3D-printed composite parts containing short fibers are inferior to those of continuous-fiber reinforced composites. However, 3D printing of short-fiber composites is more economical and feasible by direct printing with low-cost commercially available 3D printers. The use of fiber-reinforced composites and nanocomposites in 3D printing has been widely This invited article is part of a special topical focus in the Journal of Materials Engineering and Performance on Additive Manufacturing. The issue was organized by Dr. William Frazier, Pilgrim Consulting, LLC; Mr. Rick Russell, NASA; Dr. Yan Lu, NIST; Dr. Brandon D. Ribic, America Makes; and Caroline Vail, NSWC Carderock. Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s11665-02 1-05635-1. Sithiprumnea Dul, Luca Fambri, and Alessandro Pegoretti, Department of Industrial Engineering and INSTM Research Unit, University of Trento, Via Sommarive 9, 38123 Trento, Italy. Contact e-mail: [email protected]. JMEPEG (2021) 30:5066–5085 ÓThe Author(s) https://doi.org/10.1007/s11665-021-05635-1 1059-9495/$19.00 5066—Volume 30(7) July 2021 Journal of Materials Engineering and Performance
High-Performance Polyamide/Carbon Fiber Composites for Fused Filament Fabrication: Mechanical and Functional Performances
Jun 24, 2023
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