Experimental study on the dynamic compression behaviors of steel-polyethylene hybrid fiber reinforced engineered cementitious composites under combined static-dynamic loading

In actual engineering structures, static and dynamic loads frequently coexist. To enhance the physical and mechanical properties of engineered cementitious composite (ECC) materials and improve their durability, this study prepared six types of steel-polyethylene hybrid fiber reinforced engineered cementitious composites (ST/PE-HFRECC) by incorporating varying volume contents of steel and polyethylene (PE) fibers. Dynamic compression tests were conducted at three loading rates using a split Hopkinson pressure bar capable of pre-applied static loads. The experimental results are summarized as follows: (1) The dynamic compressive strength, dynamic peak strain, pre-peak toughness, and dynamic increase factor (DIF) of ST/PE-HFRECC exhibit significant strain rate strengthening effects under combined static and dynamic loading. Specifically, a pre-applied static load at the 15 % level can enhance the dynamic compressive strength of the material. Moreover, under the 30 % and 45 % pre-applied static loads, the increase in the dynamic peak strain becomes more pronounced. The DIF reaches its peak value when the pre-applied static load is at the 15 % level. (2) The damage extent of the specimens increases with higher pre-static load levels. Steel fibers primarily bridge large cracks, while PE fibers bridge micro-cracks. (3) Pre-applied static loads exhibit both weakening and strengthening effects on the dynamic mechanical properties of ST/PE-HFRECC. Consequently, studying the dynamic mechanical behavior of hybrid fiber-cement composites under static and dynamic loading conditions is not only beneficial for evaluating structural safety but also provides crucial insights for the design of structural components.