Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150949

150949 - Improving the Interlayer Bonding Strength of Additively Manufactured Polymer Composites via an Alternating Thermal Stimulus 

Additive manufacturing of polymer composites offers many benefits over traditional composite manufacturing methods. Existing methods for composite manufacturing involve costly tooling and long, energy-intensive processes. This results in high manufacturing costs, limited design complexity, and slow production rates. In contrast, additive manufacturing is rapid, scalable, and material-efficient, decreasing manufacturing time and reducing energy consumption. One such method is 3D printing of thermoset polymers via in-situ polymerization using a thermal stimulus. These thermoresponsive thermoset polymers cure by a polymerization reaction when exposed to heat. Utilizing a low-power laser source, the polymer is heated and cured in-situ during the printing process. However, a major weakness of additive manufacturing processes is the anisotropic properties resulting from relatively weak bonding between subsequent layers. This work aims to improve the interlayer bonding strength of 3D-printed composites by varying the intensity of the thermal stimulus and cure along the printed region. By pulsing the laser during printing, sections of each layer are left uncured, while other sections are fully cured. When the next layer is deposited, the fully cured sections overlap the uncured sections of the previous layer, allowing both layers to cure together via local thermal processing. This method is expected to result in significantly better bonding strength compared to layers that are fully cured upon deposition. This 3D printing process involves extruding resin ink via a three-axis gantry system. A laser attached to the print head is pulsed in short increments to cure specific sections of each layer. Once the printed samples are prepared, they are tested using a custom-designed tensile testing system to determine the interlayer bonding strength. The samples will be fixed in the center of a traditionally manufactured ASTM tensile testing specimen and pulled to failure, which is expected to occur along the layer lines of the part. The samples will be compared to control specimens produced with the laser continuously on, as well as samples with the laser entirely on or off in alternating layers. Our hypothesis is for the samples with the pulsed laser to perform the best, as the subsequent layers will bond strongly by curing simultaneously. The specimens are tested using differential scanning calorimetry (DSC) to verify that the printing process results in fully cured parts. The parts are expected to be fully cured, due to the propagation of the polymerization reaction through the layers of the part. This method of laser pulsing is expected to significantly improve the interlayer bonding strength of 3D printed polymers, eliminating a major weakness of additively manufactured composites. 

Presenting Author: Leo Allen Colorado State University

Presenting Author Biography: Leo Allen is an undergraduate summer research student with Colorado State University, advised by Professor Mostafa Yourdkhani. He is also an undergraduate student at Case Western Reserve University pursuing a degree in mechanical engineering, with a minor in computer science. Leo is passionate about the field of manufacturing and automation, and is currently performing research in additive manufacturing of composite materials.

Authors:

Leo Allen Colorado State University
Carter Dojan Colorado State University
Mostafa Yourdkhani Colorado State University