Multi-axis 3D printing of L-shaped honeycomb sandwich structure with continuous carbon fiber reinforced composites

Continuous carbon fiber reinforced composites (CCFRCs) sandwich structures are renowned for their exceptional bending stiffness and strength, making them ideal for aerospace and automotive applications. However, the design and fabrication of curved honeycomb composite structures remain challenging due to limitations of traditional mold-based manufacturing techniques. In this study, a multi-axis robotic 3D printing process for CCFRCs was established to fabricate curved honeycomb sandwich structure with variable reference surfaces, by taking L-shaped beam as an example. Two path planning strategies, normal offset and coaxial projection, were proposed for the top/bottom facesheets and honeycomb cores with controllable gestures of printing head. Three-point bending tests were conducted to analyze the bending behavior of L-shaped curved honeycomb sandwich structures with different curvature radii and path planning strategies. The results indicate both strategies effectively ensure bonding between the core and facesheets, and the bending stiffness increases with the curvature radius. Notably, the bending strength of structure formed by coaxial projection is more sensitive to curvature changes. When the curvature radius changes from 30 mm to 6 mm, the bending strength difference between the two strategies reaches 51.55 %. These studies provide valuable insights for the design and fabrication of curved honeycomb sandwich structures.