3D Printing of Continuous Fiber/ Acrylate Resin-Based Thermoset Composites

Carbon fiber reinforced polymer composites (CFRP) are attractive candidates for different engineering applications due to their exceptional stiffness, strength, toughness, chemical stability, corrosion resistance, and low weight. The combination of these desirable properties and the recent advances in additive manufacturing has motivated researchers to investigate 3D printing technologies for CFRP composites in order to overcome some of the challenges associated with their traditional manufacturing processes. Most of the reported works in the literature (that focused on the 3D printing of short/ continuous CFRP composites) utilized the fused filament fabrication technique where a thermoplastic filament is fed into a print-head, melted at high temperature, and eventually extruded onto the print bed in a layer by layer manner. In this work, we report the direct ink writing of continuous Carbon fiber-reinforced composites with UV-curable thermosetting resins. Our printer consists of a print-head (that can move on the XZ plane and serves as the ink container) and a moving stage (that moves along the Y direction and serves as the print bed). During printing, commercially available continuous Carbon fiber tow (without any sizing/ pre-treatment) is impregnated with UV-curable acrylate ink inside the print head and then extruded onto the print bed (at room temperature) where it is cured with a UV light source. We investigated the effects of resin viscosity, shear-thinning agent, deposition pressure, printing nozzle size, and printing speed on the print quality of composite filaments and Carbon fiber volume fractions. We characterized the mechanical properties of composite specimens and printed different types of complex 3D structures such as star pentagon, interconnected quadrilaterals, models of structural load-bearing components, woodpile, and honeycomb lattice structures. We also demonstrated the conformal coating of curved 3D surfaces through the printing of composite filaments. For this, we developed an algorithm to generate the print path (filament printing direction, curvature profile, and interfilament distance) based on the contour of the 3D surface to be coated. Then we optimized the print speed, deposition pressure, nozzle size, and resin viscosity to print curved composite filaments along the prescribed print path. The findings reported in this work could contribute toward the rapid design and manufacturing of components with new and emerging functionalities for the automotive, defense, and aerospace industries.