Hybrid Manufacturing of Epoxy-Infused Lattice Structures for Marine Use

Material Extrusion (MEX) is among the most accessible Additive Manufacturing (AM) processes but remains limited by low mechanical strength, directional anisotropy, and poor water resistance. This study introduces a hybrid manufacturing method that integrates MEX-printed thermoplastic lattice structures with epoxy resin infusion to overcome these limitations and achieve near-isotropic, high-strength performance. Lattice geometries, including gyroid, body-centered cubic (BCC), and simple cubic (SC) infill patterns, were designed and fabricated using Acrylonitrile Butadiene Styrene (ABS), Carbon Fiber (CF) ABS, and Fiberglass (FG) ABS filaments. Following fabrication, the specimens were vacuum-infused using a custom magnetically actuated epoxy infusion system to ensure complete void filling and structural sealing. All mechanical evaluations were performed under ASTM tensile and compression standards. The results demonstrated that epoxy-infused lattice specimens significantly outperformed solid plastic counterparts in both tensile and compressive strength while reducing anisotropy. CF ABS and shell-based geometries provided the most consistent mechanical enhancement, and fracture surface analysis confirmed that continuous epoxy penetration played a critical role in crack arrest and damage tolerance. This scalable, low-cost hybrid process bridges the gap between polymer AM and composite manufacturing, enabling the creation of waterproof, structurally efficient components suitable for marine and underwater applications. Future research aims to incorporate advanced thermoplastics, Carbon Nanotube (CNT)-reinforced epoxy systems, and numerical validation through an underwater drone case study to further advance mechanical modeling and design optimization for hybrid AM systems.