Study of Effects of Type and Amount of Steel Fibers and Diameter of Projectile on Impact Behavior of UHPSFRC

In this study, firstly the impact behavior of a kind of ultra-high performance steel fiber reinforced concrete (UHPSFRC) with one and two percent steel fiber by concrete volume are investigated under drop-weight test by using of constraint and simple supports condition. The results of tests show that fiber content has a significant effect on impact behavior of UHPFRCs, so that by increase of fiber content from one percent to two percent, the numbers of drops required to final failure of concrete targets are becoming nearly two times. Then, impact and penetration of high velocity projectile on UHPSFRC targets has been simulated by using of LS-DYNA software based on erosion algorithm. In this study, Elastic-Plastic Hydrodynamic material model has been used to modeling the behavior of concrete. This material model is able to consider the softening behavior of material due to post-yield damage by getting tabulated effective stress and effective plastic strain. Comparison between numerical and experimental results shows that the hydrodynamic model is able to describe the responses of UHPSFRC under impact loading. Besides, by adding of more fibers, concrete targets can obtain greater toughness due to higher residual strength and greater strains. It leads to reduce the penetration depth and the diameter of the cavity that are created in target due to impact of the projectile and spread of stress waves.