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

Paper Number: 150821

150821 - Additive Manufacturing of Thermoset Polymer Composites via In-Situ Thermal Curing 

Carbon fiber polymer composites (CFPC) are utilized in various industries, including aerospace and automotive, due to their remarkable lightweight characteristics and high strength and stiffness. However, traditional manufacturing techniques for CFPCs utilizing thermoset resins must be cured at elevated temperatures using an oven or autoclave. These bulk thermal curing processes are energy intensive, require long cure cycles, and limit final part size to the dimensions of the utilized curing equipment. Additionally molds or tooling are required to define the part geometry, limiting part geometry, restricting design changes, and contributing significantly to the production cost.

Additive manufacturing (AM) is a promising alternative technique for rapid and cost-effective manufacturing of CFPCs. Using AM to manufacture CFPCs reduces or eliminates the need for tooling, and significantly reduces the required time and labor for part production. Furthermore, AM facilitates the creation of complex geometries that are impossible to achieve using conventional techniques Commonly used approaches for AM of CFPCs include fused filament fabrication with thermoplastic matrices or UV-curable thermoset systems, but these approaches generally result in final parts with poor concentrations of fibers, poor mechanical properties, or a post cure in the case of UV-cured material.

This work presents an alternative approach using a thermoresponsive thermoset resin cured instantaneously in-situ via an external energy stimulus. This technique deposits discontinuous or continuous carbon fibers impregnated with the resin from a nozzle of a printing robot and then cures the material in-situ after deposition, resulting in a ready to use part. The developed process requires no post curing step, eliminating the need for expensive equipment and removing restrictions on part dimensions. Due to instantaneously curing and rigidizing the material, AM of CFPCs can be performed both on a tooled surface or freeform in-the-air without the need for support materials or tooling. Combining the ability to freeform print with robotic systems allows for the creation of complex geometries that are not achievable using conventional manufacturing processes.

To verify the thermoset material is being fully cured during the printing process, differential scanning calorimetry was used and found the printed CFPCs reached above 95% degree of cure at print speeds up to 1.5 m/min. The quality of the printed CFPCs was analyzed via digital microscopy showing high fiber content between 50-70% and a low void content of 0.5%. Mechanical properties were assessed using flexural testing and dynamic mechanical analysis. The developed process enables AM of fully cured, high quality CFPCs at printing speeds up to 1.5 m/min without necessitating any post-production processing or post-curing.

Presenting Author: Carter Dojan Colorado State University

Presenting Author Biography: Carter is a PhD student at Colorado State University in the School of Materials Science and Engineering. His research is focused on advanced manufacturing of fiber reinforced composite materials.

Authors:

Carter Dojan Colorado State University
Morteza Ziaee Colorado State University
Alireza Masoumipour Colorado State University
Mostafa Yourdkhani Colorado State University