Modeling the through-thickness frontal polymerization of unidirectional carbon fiber thermoset composites: Effect of microstructures

The frontal polymerization is a technique that creates a self-sustaining “cure front” that propagates through the thermoset resin material. Such a technique is potentially capable of substantially reducing the curing time of thermoset resin fiber composites from several hours to only a few minutes or even seconds, which is promising for the additive manufacturing and repair of thermoset fiber composites. In this study, the effect of the microstructures (i.e., fiber volume fraction, fiber tow size, and fiber tow shape) of unidirectional fiber composites on the frontal polymerization initiated in the through-thickness direction of the composites is investigated through computational modeling. The computational model is verified through comparisons with experimental data. The simulation results show that the frontal polymerization process is largely affected by the fiber volume fraction and the fiber tow shape and is insensitive to the fiber tow size. The average front velocity decreases significantly as the fiber volume fraction increases from 0% to 30% and then decreases mildly from 30% to 46%. Above 46%, the average front velocity plateaus. Moreover, the average front velocity decreases in an approximately linear fashion as the ratio between the major radius and minor radius of the elliptical cross section of fiber tow increases.