Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 99015

99015 - Buoyancy-Induced Convection Driven by Frontal Polymerization 

Frontal polymerization (FP) has been proposed to be a fast, energy-efficient, and environmentally friendly method for producing high-performance thermoset polymers, which is associated with a self-propagating exothermic reaction wave. The proposed study investigates the potential of realizing spontaneous morphogenic manufacturing with FP in buoyant fluid convection with a comprehensive study in numerical simulations and experiments. The research was done on low-viscosity monomer dicyclopentadiene (DCPD) with buoyancy-driven fluid convection, which affects the front propagation in terms of wavelength and magnitudes, resulting in tunable and distinct thermal-chemical patterns.

For numerical simulation, reaction-diffusion thermo-chemical equations written in temperature and degree of cure were coupled with the incompressible Navier-Stokes equation as governing partial differential equations. The system was solved using a designed multiphysics finite element solver with a core principle that the viscosity change of DCPD is driven by the degree of cure. The numerical simulations reported how high thermal gradients across the propagating front sustain fluid convection ahead of the front during the polymerization process transforming the DCPD liquid monomer into solid polymers. The reaction-diffusion dynamics were impacted by the natural fluid convection and thus, led to distinct front shapes as well as inclination angles. Experimental results showed high compliance with the simulation results demonstrating similar phenomena. Particle image velocimetry (PIV) was used to capture the velocity field of the fluid, front velocities, and front inclination angle in experiments to compare with numerical results.

A few dimensionless numbers were obtained by non-dimensionalizing the governing partial differential equations, which include the frontal Rayleigh (Ra) number measuring the effect of buoyancy with frontal polymerization. Ra was used to describe the proposed FP system with both numerical and experiment results supporting that the fluid momentum and front inclination angle linearly increase with the frontal Rayleigh number. To validate the scaling relationships, detailed numerical analyses and experiments were conducted under various initial temperatures and pre-gelling states.

Instability was observed in the system with higher Ra featuring multi-head spin modes near the front and led to chemical and thermal patterns in the FP domain. The wavelength of the chemical patterns and magnitudes of the thermal patterns were used to characterize the instability and were both affected by Ra. In addition, as Ra increases, one-way spinning modes were observed in comparison to the two-way spinning mode resulting in lower Ra, generating distinctive thermal and chemical patterns. Morphogenic manufacturing designs can be achieved by manipulating the reaction-diffusion dynamics and fluid convection.

Presenting Author: Manxin Chen University of Illinois at Urbana-Champaign

Presenting Author Biography: I'm a senior student at the University of Illinois at Urbana-Champaign Aerospace Engineering department. I'm currently an undergraduate research assistant in Professor Philippe Geubelle's research group.

Authors:

Manxin Chen University of Illinois at Urbana-Champaign
Yuan Gao University of Illinois Urbana-Champaign
Justine Paul University of Illinois Urbana-Champaign
Nancy Sottos University of Illinois Urbana-Champaign
Geubelle Philieppe University of Illinois Urbana-Champaign