New publication: Effect of fiber content and fiber orientation on mechanical behavior of fused filament fabricated continuous-glass-fiber-reinforced nylon

Effect of fiber content and fiber orientation on mechanical behavior of fused filament fabricated continuous-glass-fiber-reinforced nylon

1. Luke^a, D. Soares^a,b, J. Marshall^a, J. Shedden^b, O. Keles^a*

 ^aDepartment of Chemical and Materials Engineering, San José State University, 1 Washington Sq, San José, CA 95192, United States

^bTenCate Advanced Composites, 18410 Butterfield Blvd., Morgan Hill, CA 95037, United States

Rapid Prototyping Journal, 2021, In press.

https://www-emerald-com.libaccess.sjlibrary.org/insight/content/doi/10.1108/RPJ-01-2021-0003/full/html

Abstract
Purpose – Fused filament fabrication of continuous fiber reinforced polymers is a promising technique to achieve customized high-performance compos- ites. However, the off-axis tensile strength and Mode I fracture toughness of fused filament fabricated (FFFed) continuous-glass-fiber-reinforced (CGFR) nylon are unknown. This study investigated the mechanical and fracture behav- ior of FFFed CGFR nylon with various fiber content and off-axis fiber alignment.    Design/methodology/approach – Tensile tests were performed on FFFed CGFR-nylon with 10.7, 22.4, and 33.5 fiber vol. %. Tensile strength (TS) was tested with fiber orientations between 00 and 900 at 150 intervals. Double can- tilever beam tests were performed to reveal the Mode I fracture toughness of FFFed composites.
Findings – TS increased with increasing fiber vol. % from 122 MPa at 10.7 vol. % to 291 MPa at 28 vol. %. FFFed nylon with a triangular infill resulted in 37 vol. % porosity and a TS of 12 MPa. Composite samples had 11-12 vol. % porosity. TS decreased by 78 % from 291 MPa to 64 MPa for a change in fiber angle θ from 00 (parallel to the tensile stress) to 150. TS was between 27 and 17 MPa for 300 ď θ ď 900. Mode I fracture toughness of all the composites were lower than „332 J/m2.
Practical implications – Practical applications of FFFed continuous fiber re- inforced (CFR) nylon should be limited to designs where tensile stresses align within 150 of the fiber orientation. Interlayer fracture toughness of FFFed CFR composites should be confirmed for product designs that operate under Mode I loading.
Originality/value –The first study showing a) the effects of fiber orientation on the mechanical behavior and b) effects of the fiber content on the Mode I frac- ture toughness of FFFed CGFR nylon.
Keywords FDM, fused deposition modeling, porosity, unidirectional fiber composite, additive manufacturing