Curvilinear variable stiffness 3D printing technology for improved open-hole tensile strength

Abstract

Fused Filament Fabrication (FFF), one of the most popular processes of 3D printing, offers flexibility in manufacturing and introduces anisotropic properties to the final parts. With the use of Curvilinear Variable Stiffness (CVS) 3D printing technology, mechanical properties of the manufactured products can be further improved and optimized. In this work, we demonstrate how CVS design can improve open-hole tensile strength and failure strain of the manufactured specimens per ASTM D5766. In addition, the ratio of the specimen width to the hole diameter is considered as a design parameter and investigated. It is found that CVS design improves the failure strength by 38.0% for a larger hole diameter configuration (from 48.0 MPa to 66.2 MPa), while the improvement in failure strain (from 0.0125 mm/mm to 0.0130 mm/mm) is limited to only 4.0%. On the other hand, for a smaller hole diameter case, a substantial improvement of 52.5% in failure strain is obtained with the use of CVS design (from 0.0141 mm/mm to 0.0215 mm/mm), while 16.7% improvement in failure stress (76.0 MPa to 88.6 MPa) is less pronounced.