Multi-scale impact resilient smart composites (MIRACs) for hazard mitigation
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There is an increasing need to engineer structures resilient to multiple hazards, especially extreme dynamic loading such as impact, blast, and seismic loads. Material innovations in composites play an important role to meet this need. A two-phase experimental program has been developed, and it focuses on the discovery of Multi-scale Impact Resilient smArt Composites (MIRAC) while: (1) optimizing the impact toughness and fiber volume fraction; and (2) providing valuable experimental data on MIRACs. The Phase-I experimental program determines the compressive, tensile, and flexural strength of 15 specimen groups, as well as the impact toughness of MIRACs including carbon nanofibers. Based on a small-scale repeated impact test performed, the multi-scale fiber reinforced composites lead to increased impact resilience by tenfold. The Phase-II experimental program includes a drop-weight impact test of ten half-scale fiber reinforced composite beams. A steel impactor weighing 227 kg is dropped freely from a height of 6.1 m with an estimated velocity of 10.93 m/s. The results from the Phase-II test indicate that providing multi-scale (macro, micro, and nano) fiber reinforcement is essential to achieve a significant increase in impact resilience of cementitious composites as they effectively bridge different scale cracks and prevent coalescence of cracks.