Multiphysics modeling of frontal polymerization-assisted layer-by-layer additive manufacturing of thermoset polymer components

Abstract

Frontal polymerization (FP) is a novel curing strategy that relies on a self-propagating exothermic reaction front to polymerize thermoset resins rapidly. Due to its energy-efficiency and rapid curing of thermosets, a series of applications related to polymer and polymer composite manufacturing have been developed based on FP, in particular additive manufacturing (AM). While the current research demonstrates successful printing of 1D, 2D and 3D structures based on FP, a key challenge is the determination of the printing parameters through trial-and-error, which hinders its large-scale application. To better understand how different process parameters affect the front behavior and the printing process, and eventually enable fast printing of complex parts without trial-and-error, computational modeling of the printing process is highly desired. For the first time, we develop a multiphysics finite element model for simulating FP-assisted AM which accounts for both the thermal-chemical process and the ink deposition in a real printing process. To simulate the dynamic ink deposition process, element activation is used that constantly adds elements to the simulation domain following a predefined printing path and velocity. A coupled thermo-chemical partial differential equation system is solved over the changing ink domain to simulate the heat transfer and chemical reaction during the printing process. The model is first validated by comparing the front temperature history during the printing process with the experimental infrared thermal measurements. The validated model enables the determination of proper printing velocity range, within which the polymerization front can follow the printing such that the ink will not deform before curing, which is critical to ensure printing accuracy. Furthermore, the simulation reveals the change of front temperature and degree of cure between different layers, and their dependency on layer length and printing velocity, providing insights into the printing experiments for processing parameters selection.