Enhanced Mechanical Performance of 3D Printed Thermoset Composites With Bi-Modal Fiber Alignment

Abstract This study presents a new additive manufacturing methodology for short fiber reinforced thermoset composites, aimed at enhancing mechanical performance. Under complex mechanical loading, where normal and shear stresses occur simultaneously, a Bi-Modal fiber alignment approach can optimize material architecture. This method involves 3D printing composites with two fiber alignment types: aligned and random. Aligned fibers are strategically placed where one principal stress dominates, while random fibers are used when both principal stresses are similar in magnitude. The Bi-Modal 3D printing process begins with a finite element analysis to identify principal stresses under specified loading conditions. Based on this analysis, a custom G-code is generated to determine the optimal placement of aligned and random fibers according to their magnitudes and directions. Comparative tests of additively manufactured Bi-Modal composites against various fiber orientation configurations revealed significant improvements in mechanical performance. Specifically, the new Bi-Modal composite structures exhibited a 16% increase in maximum failure force. Additionally, the Bi-Modal specimens demonstrated greater fracture resistance, with longer crack paths that were at least 20% more extensive than any of the other configurations. Overall, this research highlights the substantial mechanical performance improvements achievable through principal stress-based Bi-Modal composite printing in 3D-printed CFRP structures.