Additive Manufacturing of Frontally-Polymerizable Continuous Carbon Fiber Tow-Based Composites

Additive manufacturing (AM) of high-performance thermoset polymer-matrix composites has important applications in many fields, including the aerospace, energy and automotive industries. Current AM methods for thermoset composite often require a thermal post-cure or result in lower mechanical properties compared to conventional composite manufacturing techniques. Frontal polymerization (FP) presents an alternative curing strategy that utilizes a self-sustaining exothermic reaction that propagates through a monomer as a front to convert it to a hardened thermoset polymer. In this work, we develop an extrusion-based AM process to deposit dicyclopentadiene (DCPD)-impregnated carbon fiber tows which undergo FP. The tow is deposited on a thermally conductive, heated bed to supply the thermal energy required to initiate FP. We investigate the effect of bed temperature on the front speed, front temperature, and degree of cure of the printed composite tows. A finite-element model based on a homogenized thermo-chemical formulation is developed to capture the deposition of the tow on the substrate, the heat transfer in the tow, the cure kinetics of the matrix material, and the impact of key process parameters, including the fiber volume fraction, bed temperature and deposition speed. This numerical model is then used to predict the front properties and maximum degree of cure, and is compared to experimental results.