Malik A. Blackman

(Advisor: Prof. Meisha L. Shofner)

will propose a doctoral thesis entitled,

Exploring Fast Scanning Calorimetry as a Materials Screening Tool for Laser Powder Bed Fusion

On

Tuesday, December 10 at 11:00 a.m.

MRDC Room 2405

Abstract

While standard manufacturing remains the default method for material processing, additive manufacturing (AM) continues to see greater adoption in various application fields due to lower cost of production, decrease in time of fabrication, and increase in part complexity. Additive manufacturing (AM) continues to be favored over standard manufacturing due to lower cost of production, decrease in time of fabrication, and increase in part complexity for a number of materials. Out of the seven AM techniques that are available, laser powder bed fusion (PBF-LB) has been advocated due to its low anisotropy and no support structures required for printing. Considering PBF-LB, the polymer material library is currently dominated by polyamides. While it allowed for the exponential growth of AM as an alternative manufacturing technique, polyamides are not the ideal polymer for every application. There has been exploration into other polymer families other than polyamides however, but there is still a desire to add more polymers to the list for the ever-growing application areas for this material. Current processes involve characterization techniques to predict the thermal behavior of candidate materials, such as differential scanning calorimetry (DSC). However, the laser sintering involved PBF-LB on the order of degrees per second, while the DSC has heating rates on the order of degrees per minute.

Fast Scanning Calorimetry (FSC) is an alternative calorimetry technique that can reach heating rates up to tens of thousands of degrees per second. FSC has the potential to enhance the material screening of polymer powders by simulating the PBF-LB heating environment. A robust temperature protocol in FSC would then allow for accurate observations of material behavior and kinetic evolutions at rates comparable to laser sintering. Nonetheless, how laser parameters will correspond with temperature protocols to ultimately improve final end-part mechanical properties remain unresolved. Understanding the polymer structural evolution during heating will allow for more complex studies to investigate single layer and multilayer fusion PBF-LB printing as well. The type of polymer molecular structure observed in FSC experiments will depend on the particle dimensions of the commercially available powders and their coalescence behavior, the rates performed during experimentation, and accurate simulation of the PBF-LB heating environment. The proposed goal of this research is to investigate the capabilities of utilizing FSC as an alternative characterization tool to screen candidate polymer powders for their compatibility with PBF-LB by simulating the AM technique’s heating and cooling environment to uncover the expected material fusion behavior a priori. This proposal has three aims: (1) investigating the kinetic crosslinking evolution in select thermosets (2) investigating particle coalescence and crystallization dynamics in PBF-LB through temperature and laser parameter modulation and (3) Utilizing computational simulations to develop process-structure-property relationships with FSC. The successful outcomes with these aims will lead to a more robust methodology for material screening of candidate polymer powders for PBF-LB.

Committee

• Prof. Meisha L. Shofner – School of Materials Science and Engineering
• Dr. Camden A. Chatham – Savannah River National Laboratory 
• Prof. Natalie Stingelin – School of Materials Science and Engineering
• Prof. Tequila Harris – School of Mechanical Engineering
• Prof. Donggang Yao – School of Materials Science and Engineering