Doctor of Philosophy
Civil and Environmental Engineering
Moncef L. Nehdi
Extreme loading events such as impact, blast, and earthquakes have often led to partial or total collapse of structures, associated with economic and human life loss. Therefore, civil engineers have been seeking innovative materials and systems that would allow designing resilient and smart structures which can withstand such catastrophic events. Recently, engineered cementitious composites (ECC) and shape memory alloys (SMA) have emerged as strong contenders in the production of smart and resilient structural systems.
The aims of this study are to explore the possible synergy between ECC and SMA for developing a novel hybrid fibre-reinforced ECC incorporating randomly dispersed SMA and polyvinyl-alcohol short fibres (HECC-SMAF) with possible strain recovery and superior impact resistance. The mechanical properties of the composite, including uniaxial tensile and strain recovery performance, were examined. Moreover, the behaviour of the composite under impact loading was explored using a drop weight impact test. Test specimens were also heat-treated to investigate possible pre-stressing effects of SMA fibres on the impact resistance of the ECC. A two-parameter Weibull distribution was used to analyze variations in experimental results in terms of reliability function. Furthermore, numerical simulation was developed to predict the behaviour of the composite under impact loading.
Results indicate that SMA fibres significantly enhanced the performance of the composite both under static and dynamic loading. Adding fibres beyond a certain dosage led to fibre clustering, thus, no further gain in tensile and impact performance was measured. The impact resistance of HECC-SMAF specimens was further improved after exposure to heat treatment. This highlights the significant contribution imparted by the local pre-stressing effect of SMA fibres to the impact resistance of the composite. The Weibull distribution was adequate to predict the impact failure strength of the new composite, allowing to avert additional costly experiments. Also, numerical simulation predictions of the impact behaviour of the hybrid composite were in good agreement with experimental findings, thus offering a suitable predictive tool and allowing to preclude costly and time-consuming experiments.
This research underscores the potential to engineer new cementitious composites with superior tensile properties and impact resistance for the protection of critical infrastructure in the event of explosive or impact loading.
Ali, Mohamed Ali El-Sayed Mahmoud, "Tensile and Impact Behaviour of Shape Memory Alloy Fibre Reinforced Engineered Cementitious Composites" (2017). Electronic Thesis and Dissertation Repository. 4650.