## 8 Conclusions  
Experimental testing and numerical simulations were carried out in the present study to investigate the behavior under impact loading of a novel composite endowed with strain recovery, which is made of an engineered cementitious composite incorporating hybrid SMA and PVA short fibers. Impact loading was conducted at different drop levels using a drop weight impact test, and numerical simulations of the composite's impact behavior were performed. The following conclusions can be drawn based on this research:  
* The tensile properties of the ECC composite were generally enhanced owing to SMA fiber addition. All ECC mixtures achieved a tensile strain of up to 8%. Among the tested mixtures, the  
Figure 26: Impact energy sustained by composite specimens: (**a**) 1 st crack and (**b**) failure. composite incorporating 2% PVA and 1% SMA fibers achieved the highest tensile properties and impact resistance. * Generally, the impact resistance of the composite was improved owing to SMA fiber addition. Upon multiple impacts, the energy dissipation capability of the HECC-SMAF composite was increased by about 23.39%, 30.43%, and 11.53% owing to SMA fiber addition of 0.5%, 1%, and 1.5% by volume fraction, respectively, compared to that of the ECC specimen incorporating 2% PVA fibers alone. * The impact penetration depth tended to decrease upon SMA fiber addition. For instance, the ECC2-0.5, ECC2-1, and ECC2-1.5 specimens had 6.3%, 10.1%, and 2.6% lower penetration depth compared to that of the control PVA-ECC specimen, respectively. * The heat treatment process led to the melting of the PVA fibers with the associated loss in mechanical properties. Yet, the heat treatment stimulated the SMA fibers to locally prestress the composite's matrix owing to its shape memory effect. Consequently, an overall enhancement in the energy absorption capacity of the heated HECC-SMAF hybrid composite over that of its non-heated counterpart was observed. * The superior impact performance of the hybrid composite and similar composites [50] make such novel materials the strong contenders for constructing protective structures, with a potential to enhance the safety of critical infrastructure assets against explosions and impact events. * Plasticity models, coupled with the add-erosion option and maximum principal strain, were appropriate for simulating the behavior of the ECC composite under impact loading. * The numerical simulation results using the Concrete Damage Plasticity were in closer agreement with the corresponding experimental data than that of the Drucker/Prager model in terms of energy dissipation capability and maximum penetration depth. The numerically estimated results in terms of the energy dissipation ability using the CDP and DP models were 24.4% and 61.5% lower than that of the corresponding experimental data, respectively, while it was higher than that of the corresponding experimental data by 12.1% and 25.1% in terms of the total penetration depth, respectively. * Generally, the stress distribution, crack propagation, and failure criterion of the numerically simulated ECC specimens were in good agreement with the experimentally observed behavior of the ECC specimens under impact loading. However, the tolerance in the applied impact load evaluated using the DP model was about four times that of the CDP model compared to that estimated experimentally. * This study demonstrates the feasibility of using numerical simulation to reasonably predict the behavior of the hybrid composite developed in this study under impact loading. The model can be further enhanced to capture additional aspects related to the fiber type, dosage, strain rate, and other relevant parameters that were not within the scope of the current study. Developing a comprehensive and robust model can save time, effort, and cost associated with laborious experimental testing. [PERSON] developed the scientific concept of the study and its plan. [PERSON] also wrote the final version of the manuscript.