Session: 03-08-02: Computational Modeling and Simulation for Advanced Manufacturing

Paper Number: 145087

145087 - Computational Model of Resin Curing Kinetics in Volumetric 3d Printing of Soft Structures 

Volumetric 3D printing (V3DP) has garnered considerable interest recently due to its potential to overcome some of the limitations of conventional layer-by-layer additive manufacturing techniques. Specifically, V3DP offers relatively fast print times, isotropic material properties, smooth surface finish, and the ability to print soft, complex structures without the need for support structures. Furthermore, V3DP technology has the potential to simultaneously print multiple materials and is compatible with a wide range of soft structures, including flexible foams, elastomers, hydrogels, and rubbers. The technology thus opens opportunities for numerous applications including soft robots and critical biomedical structures and implants. In particular, advancement in V3DP for bioprinting holds promise for personalized medicine and tissue engineering. However, this technology is still in its infancy with many challenges still to overcome before full-scale exploitation. This project aims to address one of such challenges by developing a numerical model of the photopolymerization curing process to systematically guide the V3DP process, an area that has received limited attention.

The curing kinetics is first modeled analytically with the relevant constants of the curing kinetic equation determined for various light intensities, temperatures, and photoinitiator concentrations from experiments utilizing a V3DP system. The thermal modeling of the printing process is then undertaken through solution of the energy equation with the above curing rate equation incorporated as a source term. Bulk convection is neglected. The boundary conditions assume insulated side wall and bottom wall, while the top surface is exposed to natural convection. The initial conditions for the stagnant resin are set using the initial resin temperature and experimentally determined resin property values as functions of local temperature. The system of equations, subject to the boundary and initial conditions, is solved with the commercial CFD solver Ansys Fluent for an axisymmetric 2D rectangular resin domain, consistent with the experimental setup. The computational model is used to predict the transient temperature distribution and the evolution of the degree of cure in the resin domain from which information regarding stress gradient, shrinkage, and cracks in the printed structure can be deduced. Due to the low thermal conductivity of resins, the temperature gradient in the resin domain, which relates to the stress distribution in the print, is expected to be significant despite the relatively low resin temperature during curing. The computational model is validated by comparison of the predicted temperatures with the experimental data obtained at specific landmarks within the resin using thermistors. The preliminary modeling results predict the general exponential and diffusive trends and patterns expected in a curing reaction and are generally in the consensus of the experimental observations.

Presenting Author: Jeevith Kanagarajan University of Central Florida

Presenting Author Biography: Jeevith Kanagarajan is currently pursuing his master's degree at the University of Central Florida under the supervision of Dr. Olusegun Ilegbusi, having previously completed his Bachelor's degree in mechanical engineering at the same institution. His research focuses on utilizing computational fluid dynamics to model the photopolymerization curing process in volumetric 3D printing, particularly in soft structures. Jeevith is passionate about learning more about volumetric 3D printing through computational methods, with potential implications for bioprinting applications.

Authors:

Jeevith Kanagarajan University of Central Florida
Olusegun Ilegbusi University of Central Florida