Effect of Loading Rate and Fiber Content on the Dynamic Compression Behaviors of Steel–Polyethylene Hybrid Fiber Reinforced Engineered Cementitious Composites

The incorporation of a single fiber into engineered cementitious composites (ECC) has relatively limited effects on improving their performance. To further enhance the physical and mechanical behaviors of ECC and improve their durability, steel–polyethylene hybrid fiber reinforced engineered cementitious composites (ST/PE-HFRECC) specimens were prepared by mixing steel fibers and polyethylene (PE) fibers by different volume fractions. Using a split Hopkinson pressure bar (SHPB), dynamic compression tests were conducted under three different loading rates. The effect of loading rate and fiber volume fraction on the dynamic compression behaviors of ST/PE-HFRECC was investigated. Based on the experimental results the following conclusions can be obtained: (1) The dynamic compressive strength, peak strain, pre-peak stress toughness, and dynamic increase factor (DIF) of ST/PE-HFRECC exhibit significant strain rate strengthening effects under dynamic loading. (2) The ST/PE-HFRECC exhibited superior dynamic performance and crack-bridging capability compared to composites reinforced solely with steel or PE fibers. Steel fibers significantly improved the dynamic compressive strength, while PE fibers better enhanced the ductility and toughness of the material. (3) Among the hybrid formulations of steel and PE fibers, the S0.5E1.5 (0.5% steel fiber and 1.5% PE fiber by volume) demonstrated optimal resistance to high rate compressive failure, reflected in reduced specimen damage, higher dynamic compressive strength, peak strain, and pre-peak stress toughness.