Out‐of‐Plane Compression Behavior and Energy Absorption Characteristics of Carbon Fiber Reinforced Epoxy Composite Honeycomb Cores With Various Cell Geometric Configurations Fabricated via Direct Ink Writing
Anirban Mondal, Mrinal C. Saha
Abstract
ABSTRACT This study explores the out‐of‐plane compression and energy absorption behavior of carbon fiber‐reinforced epoxy composite honeycomb cores with hexagonal (H), square (S), and triangular (T) geometries. These cores were fabricated using direct ink writing (DIW), a 3D printing method, with specially formulated inks containing 10–40 wt% short carbon fibers, silica, and additives. The inks were engineered to exhibit shear‐thinning behavior, enabling mold‐free printing of bioinspired structures with enhanced surface finish and dimensional precision. Mechanical properties were tailored by varying geometry, material composition, and infill density (30%–40%). Out‐of‐plane compression tests revealed improved load‐bearing capacity with increased infill density: 11.7% for hexagonal, 98% for square, and 80.8% for triangular. Crashworthiness analysis revealed square cores had the highest energy absorption (EA), outperforming hexagonal and triangular designs. Specific energy absorption (SEA of hexagonal—23–45 J/g, square—23–42 J/g, triangular—16–32 J/g) and crushing force efficiency (CFE of hexagonal—59–76, square—59–73, triangular—42–79) metrics validated the DIW‐printed cores' performance as comparable to or better than cores made from continuous fibers, metals, thermoplastics, foams, and polymers. This detailed study highlights DIW's ability to produce advanced composite honeycomb cores with customized properties, paving the way for applications in lightweight, high‐performance crashworthy structural designs.