Multiple Impact Resistance of Hybrid Fiber Ultrahigh Toughness Cementitious Composites with Different Degrees of Initial Damage

Abstract

In this research, the multiple impact resistance of hybrid fiber ultrahigh toughness cementitious composites (UHTCC) was studied. By varying the impact velocity, different degrees of initial damage were first induced in the specimens. Then the multiple impact behavior of these specimens, including stress-strain relationship, energy absorption capability, degree of damage, and microstructure of damaged material were investigated and discussed. The results revealed that hybrid fiber UHTCC specimens could maintain their integrity even though the dynamic peak stress was below 10.0 MPa, which significantly reduced the surface spalling of fragments. The specimens with a low-degree initial damage showed improved multiple impact resistance over those without initial damage, because the microstructure of specimens was densified under the low-velocity initial impact load. Through the comparison among four groups of specimens with 2.0% of polyvinyl alcohol (PVA) fiber and different volume fractions (0.0%, 0.5%, 1.0%, and 1.5%) of steel fiber, the specimens with 1.0% steel fiber showed the highest energy absorption capability and sustained the largest number of impacts.