Improvement and Characterization of Direct-Ink-Write Manufactured Continuous Fiber Reinforced Photopolymer Matrix Composites

Abstract

Fiber reinforced polymer (FRP) composites play a significant and continuously growing role in engineering applications that require high strength, weight optimized structural components. Additive manufacturing (AM) has proven to be an extremely powerful tool in expanding the limits of part complexity and optimization. The present work aims to combine the two by reliably and efficiently additively manufacturing continuous fiber reinforced thermoset polymer composites. Building off previous efforts, a novel 3D printer was refined that utilizes direct ink write (DIW) technology to simultaneously extrude both an in-situ cured UV resin and continuous reinforcing fiber. Improvements to the system ensured that the most common failures were significantly mitigated or eliminated. The capabilities of the printer, specifically the maximum print size, were also increased by a wide margin. The printer’s more predictable state allowed the creation of samples for material characterization. Tensile specimens showed strengths as high as 209 MPa and an average tensile modulus of 19.5 MPa. Volume fraction testing using carbonization in a nitrogen atmosphere gave an average fiber volume fraction of 8.3%. These are competitive with the results of other investigations of similar continuous fiber AM processes. The printed material was further characterized with scanning electron microscopy, showing that the bonding between matrix layers and resin impregnation within fibers were both ideal. Printed cones and honeycombs also showed that the process can produce complex geometry. Future efforts can serve to increase the fiber volume fraction and overall strength optimization of the printed material. The introduction of new materials into the process, like fiberglass or nanoparticles, could also change the properties of the products to have better curing behavior or higher strength.