Direct ink writing of hexagonal honeycomb carbon fiber‐reinforced epoxy composites with varying cell geometric parameters and tailored in‐plane compressive properties

Abstract This study examines the fabrication and characterization of high‐strength‐to‐density ratio, short carbon fiber‐reinforced epoxy composite honeycomb structures using Direct Ink Writing (DIW) and engineered inks. The epoxy inks, with 10–40 wt% carbon fibers and other precursors, were tailored to desired viscoelastic and shear‐thinning properties for 3D printing, enabling precise DIW printing of bioinspired hexagonal honeycomb structures. These formulated inks in combination with DIW facilitated honeycomb production with variable cell sizes and geometries without the need for molds. DIW 3D printing ensured precise material deposition, controlled composition, superior surface finish, and shape fidelity when compared to conventional methods. The mechanical performance of these structures was tailored through varying the base material composition and by changing the infill densities from 30% to 50%. In‐plane compressive testing demonstrated nominal increases of 86% in stiffness and 204% in strength for specimens printed with 20 wt% carbon fibers as infill density increased from 30% to 50%. Specific stiffness and strength showed similar trends. Comparisons with scaling laws revealed higher‐than‐expected strength, exceeding values reported in published studies. These findings showcase DIW with engineered inks as a pathway to fabricate advanced honeycomb composite structures, enabling tailored designs and properties for innovative, lightweight, high‐strength structural design and applications. Highlights Developed carbon fiber‐reinforced viscoelastic inks (10–40 wt%) for DIW. Used viscoelastic inks with DIW to create honeycombs with diverse geometries. Attained superior print quality in honeycombs over PLA/fiber composites. Compression tests showed increased stiffness and strength with higher infill. Outstanding compressive performance exceeding strength expectations.