Effect of fiber hybridization on the electromagnetic shielding of UHPFRCC panel

Interest in electromagnetic shielding of cement-based materials is increasing to protect human health and electronic equipment from electromagnetic interference (EMI). EMI shielding effectiveness of cement-based materials can be reduced by cracking, and thus cracking behavior is a major factor influencing EMI shielding effectiveness reduction of cracked cementitious composites. In this study, the effects of hybridization of fibers on the cracking behavior and EMI shielding effectiveness of non-cracked and cracked ultra-high-performance fiber-reinforced cementitious composite (UHPFRCC) were investigated. UHPFRCC containing 1.5 vol% long steel fibers was considered as a control variable, and substitution with 0.5 vol% short steel fibers, PE fibers, and carbon fibers was considered as experimental variables. Compressive strength, density, direct tensile behavior, electrical conductivity, and capacitance tests were conducted. After that, crack length, width, area, and EMI shielding effectiveness of panels that were cracked by step-by-step loading were measured. According to the test results, the effect of short steel fiber substitution was insignificant. PE fibers significantly improved tensile strain performance, but it decreased EMI shielding effectiveness when the thickness of the panel decreased. On the other hand, carbon fiber substitution decreased mechanical performance and electrical conductivity due to dispersion problems, but it improved EMI shielding effectiveness at 1 GHz by 30.0–62.9% by dielectric polarization. The total crack length at each displacement level increased logarithmically with the increase in normalized toughness, and carbon fiber substitution showed the lowest crack dispersion capacity. However, carbon fiber substitution has been shown to alleviate the degree of deterioration of EMI shielding effectiveness after cracking.