Effects of printing parameters on the quasi-static and dynamic compression behaviour of 3D-printed re-entrant auxetic structures

• Effects of various printing parameters on re-entrant structures are revealed. • Peak force and energy absorption are greatly enhanced by proper printing direction. • Including short carbon fibres in PLA increases stiffness but induces brittleness. • Nozzle diameter has minor, inconsistent effects on mechanical properties. • Failure mechanisms are affected by printing parameters, materials and loading speed. This study examines the effects of manufacturing parameters on the mechanical properties of 3D-printed re-entrant auxetic structures under quasi-static and dynamic compression conditions. The influences of base material (PLA and short carbon fibre-reinforced PLA), nozzle diameter (0.4 mm and 0.6 mm), and printing direction were systematically analysed. Experimental results revealed that peak force and energy absorption could be significantly enhanced by proper printing direction. While the addition of short carbon fibres effectively increased stiffness, it also introduced brittleness that was detrimental to energy absorption. However, the impact of nozzle diameter was relatively minor and varied with test conditions. Microscopic analysis of printing quality and fracture surface morphology provided further insights into the fundamental roles of manufacturing parameters in determining the mechanical behaviour of re-entrant structures.