Behavior of hybrid-fiber engineered cementitious composites subjected to dynamic tensile loading and projectile impact

The characteristics of engineered cementitious composites (ECCs) subjected to dynamic tensile loading and high-velocity projectile impact have been investigated and are reported in this paper. Hybrid-fiber ECC containing a combination of high-modulLIS steel fibers and relatively low modulus polyethylene fibers was adopted to achieve a desired balance between the ultimate strength and the strain capacity of the material required for impact- and blast-resistant structures. Dynamic uniaxial tensile tests at varying strain rates of 2 X 10(-6) to 0.2 s(-1) were carried out, and ECC was found to be able to provide much higher enhancement in tensile strength than plain concrete and still be able to maintain pronounced tensile strain-hardening behavior. At higher rates of strain, ECC showed multiple cracking behavior, similar to that observed from quasi-static tests, with tight crack width of about 0.1 mm. The results from high-velocity (300-750 m/s) impact tests demonstrated the potential of ECC in providing improved functionality (compared with concrete) as a protective material in aspects such as increased shatter resistance with reduction in damage arising from scabbing, spalling, and energy absorption associated with distributed microcracking.