Mechanical Reinforcement of Porous DLP 3D-Printed Structure via Epoxy Infiltration

Abstract This study presents an effective reinforcement strategy for brittle photocurable polymer structures fabricated by digital light processing (DLP) 3D printing. A porous architecture with an interconnected nanoscale pore network was generated through UV-induced phase separation using a water-soluble PEG additive. Epoxy resin was subsequently infiltrated into the porous structures by immersion and thermal curing, forming an interpenetrating composite phase throughout the internal pore channels. Quantitative mechanical testing revealed that epoxy infiltration dramatically enhanced the performance of the porous structures, resulting in an approximately 42.5 times increase in compressive strength, and 146 times increase in Young’s modulus. In contrast, the solid structures, which allowed only superficial epoxy coating, exhibited much smaller improvements of 8 times in compressive strength and 22 times in modulus. The porous/epoxy specimens further demonstrated delayed failure and multi-stage deformation, indicating significantly improved energy absorption and structural stability. These results highlight the novelty and scientific impact of the proposed method: a simple infiltration–curing process can effectively transform a DLP-printed porous resin into a high-performance composite architecture. This approach offers a practical pathway for enhancing the mechanical durability of 3D-printed polymer structures for lightweight structural, shock-absorbing, and functional composite applications.