MULTISCALE TOUGHENING MECHANISM IN HYBRID FIBER REINFORCED CEMENT-BASED NANOCOMPOSITES

In this study a thorough evaluation of the toughening mechanism in cement-based nanocomposites reinforced with hybrid networks of carbon nanofibers (CNFs) and polypropylene microfibers (PPs) took place. The critical values of fracture toughness/stress intensity factor, KIC, were experimentally determined on prismatic notched specimens of nano and micro scale fiber reinforced cementitious composites using the two parameter fracture model (TPFM). The post-crack energy absorption capacity of the hybrid-composites was assessed by evaluating the dimensionless toughness index, I20, calculated through linear elastic fracture mechanics (LEFM) tests. The addition of CNF/PP networks at low volume fractions of about 0.1 vol% in cementitious matrix results in a significant improvement in the KIC (85-240%) and 1.6 – 10x higher I20 compared to the CNF or PP reinforced materials. Relative to the single-scale fiber reinforcement, the synergy between the nano- and micro- scale fibers results in a multi-scale crack arresting distinctively increasing the toughening effect in the hybrid fiber-cementitious mortar nanocomposites.
EXTENDED ABSTRACT