07/12/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Master's Thesis defense by Mihir Nikunj Mehta on: "Polymer Foams with Spatially Variable Densities to Enable Topology Optimization in Additive Manufacturing of Cellular Material"

Candidate Name: Mihir Nikunj Mehta
Degree: Master’s
Defense Date: Friday, July, 26, 2024
Time: 10 a.m. to Noon
Location: Perry Hall, Room115

Committee:
Advisor: Amir Ameli, Ph.D., Assistant Professor, Plastic Engineering, UMass Lowell

Committee Members*
1. Jay Park, Ph.D., Assistant Professor, Plastic Engineering, UMass Lowell
2. Emily D. Sanders, Ph.D., Assistant Professor, Mechanical Engineering, Georgia Tech

Brief Abstract:
This study introduces a novel additive manufacturing method for in-situ 3D printing of thermoplastic materials featuring graded foam structures with controlled variable density. Leveraging the capabilities of topology optimization, this approach optimizes the material distribution within a design space to enhance the stiffness-to-weight ratio of printed structures. The methodology encompasses five primary stages: (1) production of expandable filaments via single screw extrusion of Polylactic Acid (PLA) and Nylon (PA12) mixed with thermally expandable microspheres (TEM) at different concentrations; (2) empirical determination of the relationships between flow rate and density, as well as density and modulus of elasticity in 3D printed foams; (3) application of topology optimization to generate designs with spatially variable density tailored to maximize structural efficiency; (4) conversion of optimized designs into modified G-code to map density profiles according to the optimized structure; and (5) the actual 3D printing of the topology-optimized foam structure. The integration of a MATLAB program to adjust the G-code enables precise control over density distribution by correlating it with specific flow rates. The resultant topology-optimized beam was successfully printed, demonstrating a close match between the predicted and actual densities, thereby validating the efficacy of the proposed method. This technique not only enhances the potential applications of 3D printed materials in various industries by allowing for customized density profiles within a single structure but also sets a foundation for further research into advanced manufacturing techniques that prioritize material efficiency and structural integrity.