Manufacturing of Continuous Carbon Fiber Composites Using Ultraviolet Laser-Assisted Direct Ink Write 3D Printing

Abstract

Additive manufacturing (AM), commonly referred to as 3D printing, is a quickly growing field with numerous techniques available to manufacture parts which are stronger, lighter, and more complex than those which could be traditionally manufactured. With the goal of creating stronger parts, a new 3D printing technique was developed which combined properties of several different methods in order to print continuous carbon fiber-reinforced thermosets. This new method is called continuous fiber direct writing (CFDW). The process works by extruding continuous fiber and ultraviolet (UV) curable resin out of a syringe simultaneously and curing the resin immediately upon extrusion via UV lasers aimed at the extrusion point. This was created using the principles behind direct ink writing (DIW), stereolithography (SLA), and fused deposition modeling (FDM). It utilizes DIW technology to extrude liquid resin out of the syringe, SLA technology to cure the resin in situ, and FDM technology to deposit the fiber and resin onto the print path. In order to test this novel method, a custom extrusion system and print head was designed and adapted onto an existing consumer FDM printer. The developed printer is able to successfully print continuous fiber-reinforced samples with control over the fiber direction and fiber volume fraction. Several experiments were conducted in order to characterize the various printing parameters. The largest focus was on the two most important parameters: deposition speed and extrusion pressure. The deposition speed, or feed rate, describes how quickly the print head moves across the build plate, while the extrusion pressure describes how much pressure is applied to extrude the resin out of the syringe. These two parameters together greatly affect the resulting width and shape of a printed line of fiber. In general, increasing the pressure or decreasing the feed rate creates a larger line width. This is very important as it affects the hatch spacing which in turn affects the fiber volume fraction. Additionally, these factors can affect the top surface finish of the resulting part. In addition to these parameter-based studies, bulk rectangular samples and complex samples were printed in order to demonstrate the capabilities of the printer. The CFDW method works well and is fairly consistent with the proper printing parameters. Through future development of this process, composite samples can be made with individual tows of fibers oriented according to the geometry of the part, allowing for reduced weight and increased strength of the additively manufactured components.