Abstract
In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites (SMAHCs) for aeronautical applications is analysed and compared by means of findings from numerical analyses and experimental tests. At first, experimental tests are performed by using a drop tower facility on both carbon fibre reinforced plastic samples and Carbon Fibre Reinforced Plastic (CFRP) samples hybridized with shape memory alloy materials. The materials properties and the different lower velocity impacts behaviours are simulated and validated by means of numerical models discretized in LS-Dyna explicit solver. For both configurations, the deformation mechanism for low intensity impacts, the absorbed energy, and the effect of rebounding upon the velocity change, and hence the amount of force, are investigated. Then, a configuration is prepared to withstand higher-energy impacts. Finally, the numerical analysis is extended for an innovative layup adapted on an aeronautical structure, which is subjected to the bird-strike phenomenon at 180 m/s and with an impacting mass of 1.8 kg according to the airworthiness requirements. In this study, SMAHCs are used to improve the composite impact response and energy absorption thanks to the superelastic effect.
Highlights
The properties of smart materials can be significantly modified by external causes, such as stress, temperature, humidity, electric or magnetic fields, and for this reason they offer unexpected potential compared to traditional ones [1]
This paper summarizes research on improving the impact performance of polymer matrix composites by embedding shape memory alloys, in order to increase the level of absorbed energy before failure, mainly ascribed to the ability of SMA materials to decrease the damage area resulting from an impact event, and due to the ability to undergo large amounts of elastic and plastic deformation, at moderately high stresses, due to the superelastic properties of TiNi shape memory alloy
The results demonstrated that hybrid composites structures embedded with shape memory alloys subjected to low velocity impacts are characterized by an increased damage resistance with respect to conventional composite structures
Summary
The properties of smart materials can be significantly modified by external causes, such as stress, temperature, humidity, electric or magnetic fields, and for this reason they offer unexpected potential compared to traditional ones [1]. This paper summarizes research on improving the impact performance of polymer matrix composites by embedding shape memory alloys, in order to increase the level of absorbed energy before failure, mainly ascribed to the ability of SMA materials to decrease the damage area resulting from an impact event, and due to the ability to undergo large amounts of elastic and plastic deformation, at moderately high stresses, due to the superelastic properties of TiNi shape memory alloy. Polymer-based composites are characterized by high strength and stiffness associated with a low weight [9,10,11] They have relatively limited applications due to their brittle behaviour, related to matrix–fibre interaction, with consequent poor performances in terms of damage resistance to impact if compared to ductile materials. The results demonstrated that hybrid composites structures embedded with shape memory alloys subjected to low velocity impacts are characterized by an increased damage resistance with respect to conventional composite structures. The impact energy is evenly distributed in the specimens by the hybrid fabric, as confirmed by the presented experimental tests
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