Energy-efficient manufacturing of multifunctional vascularized composites

The retention and transport of different fluids inside synthetic microvascular fiber-reinforced polymer (FRP) composites enable environmentally adaptive functions, including thermal regulation, self-healing, and electromagnetic modulation. However, manufacturing of vascularized components involves an energy- and time-intensive multistep process to cure the host matrix (several hours at elevated temperature) and then evacuate the embedded sacrificial template (12–24 h at 200°C under vacuum). Here, we demonstrate rapid (minutes), energy-efficient, and scalable fabrication of vascularized FRP composites at room temperature using the exothermic frontal polymerization of a dicyclopentadiene host matrix. The chemical energy released during frontal curing of the host resin facilitates the endothermic depolymerization of an embedded sacrificial thermoplastic to create structures with high-fidelity microchannels, reducing the thermal energy for fabrication by nearly four orders of magnitude compared to previous methods. The presence of fiber reinforcement in this tandem curing and vascularization strategy presents several challenges related to successful frontal curing and microchannel formation. Increasing the volume fraction of fiber reinforcement (V_f) decreases the volume of the host resin matrix, generating less energy for sustaining the curing and vascularization processes. Heat retention for several minutes after completion of frontal curing using thermally insulating tooling is crucial for obtaining clear microchannels in composite specimens with V_f = 60%. Simulation of the vascularization process confirms the slower depolymerization of the sacrificial templates in high-V_f composites. A nominal decrease in channel circularity also occurs with an increase in the compaction pressure required for high V_f of composite panels. We leverage this rapid manufacturing strategy to fabricate hybrid composites with vascular networks that span the bulk of the composite and a surface coating for potential self-healing applications.