Behaviour of a novel functionally graded 3D re-entrant lattice reinforced high-performance concrete under static and dynamic compression

This paper presents a systematic experimental study on the static and dynamic mechanical behaviour of high-performance concrete (HPC) reinforced with 3D re-entrant lattice, accounting for the effect of functionally gradient design. The uniform 3D re-entrant lattice (U) and the corresponding vertically positively and negatively graded lattices (FG1 and FG2) were designed and manufactured with 3D printing. The plain HPC (P-HPC) and HPC reinforced with U (U-HPC), FG1 (G1-HPC) and FG2 (G2-HPC) were fabricated accordingly. Static compressive and split Hopkinson pressure bar tests were then conducted to investigate the static and dynamic compressive behaviour of 3D re-entrant lattice reinforced HPC under various strain rates (i.e., 0, 28.1, 50.6, 72.0 and 100.6 s⁻¹). Results indicate that the static compressive strength of HPC specimens is slightly improved owing to re-entrant lattice reinforcement, while the static dissipated energy of P-HPC is 55.7 %, 53.2 % and 57.5 % lower than that of U-HPC, G1-HPC and G2-HPC, respectively. Regarding dynamic compressive behaviour, although the dynamic strength of P-HPC is 11.3–24.6 % higher than that of lattice reinforced HPC at a strain rate of around 30 s⁻¹, with the further increase of strain rates, the re-entrant lattice reinforced HPC presents higher strength improvement. G2-HPC has the highest dynamic compressive strength of 198.3 MPa at a strain rate of approximately 100.6 s⁻¹, followed by G1-HPC, P-HPC and U-HPC. At low strain rates, the plain and lattice reinforced HPC exhibit the similar energy absorption. When the strain rate reaches around 100.6 s⁻¹, U-HPC, G1-HPC and G2-HPC exhibit a 29.8 %, 36.8 % and 54.3 %, respectively higher dissipated energy than P-HPC. The gradient design of lattice reinforcement brings a more gradual and smooth dissipation of energy, thereby improving the overall energy absorption capacity. The excellent dynamic compressive behaviour of functionally graded 3D re-entrant lattice reinforced HPC offers a promising solution for protective structures subjected to high strain rates, including impact, blast, and seismic loadings.