# An Overview of Smart Composites for the Aerospace Sector
## 1 Introduction  
The continuous advancement of aerospace technology has pushed the need for innovative materials that enhance structural performance, fuel efficiency, and operational safety. Materials play a crucial role as safety-critical components in aerospace structures, forming the wings, fuselage, empennage, landing gear, tail boom, and rotor blades of helicopters, aircraft, satellites, or unmanned aerial systems (UAS) [1, 2]. Here, smart composites have emerged as a transformative class of materials capable of self-monitoring structural health, responding to external stimuli, and adapting to environmental conditions [3, 4]. The multi-functionality of these materials is particularly relevant in aerospace applications, where weight reduction, durability, and real-time health monitoring are crucial factors [5, 6]. There is an increasing interest in the development of adequate inspection techniques for Structural Health Monitoring (SHM) applications. Here, sensors are utilized to collect data, which is then processed and analyzed to build a control system that will be in place for the duration of an asset's life [7]. Several traditional SHM methods, including guided waves, acoustic emission, and ultrasonic, rely on intricate statistical and mathematical methods and do not provide complete real-time information regarding the condition of the structure. For this reason, it is necessary to explore other options. In this regard, smart composites present a promising solution for SHM. On the one hand, piezoelectric composites raise the ability of certain materials to generate an electric response to mechanical stress. These composites typically consist of piezoelectric ceramics (PZT, BaTiO\({}_{3}\), PbTiO\({}_{3}\), KNbO\({}_{3}\)...) embedded in a polymer matrix, allowing them to function as both sensors and actuators [8, 9]. On the other hand, piezoresistive composites incorporate conductive elements such as carbon or metal nanoparticles in polymer matrices, which enable real-timemonitoring of structural integrity through changes in their electrical properties. The reason for interest is that, as has been well documented, their incorporation into these insulating systems enables the development of percolating electrical networks, fostering a widespread improvement in electrical conductivity [10; 11; 12]. More specifically, the electrical properties of these nanocomposites are primarily influenced by three key factors: the intrinsic resistivity of the nanoparticles, the contact resistance between adjacent particles, and the tunneling effect occurring between neighboring nanoparticles [13]. This means that their electrical resistivity changes when subjected to damage or mechanical strain. Recent studies have also focused on the development of electromagnetic interference (EMI) shielding composites that enhance the resilience of aerospace electronics. With the increasing reliance on electronic systems in modern aircraft, protecting sensitive avionics from external electromagnetic disturbances is a growing priority [14; 15]. Carbon-based nanomaterials, such as graphene and carbon nanotubes, have demonstrated exceptional EMI shielding capabilities while maintaining mechanical integrity, making them ideal candidates for next-generation aerospace applications [16; 17]. In addition, smart composite-based adaptive and morphing structures are opening opportunities for revolutionary improvements in flight performance and aerodynamics. These structures can alter their shape in response to external stimuli, such as temperature changes or aerodynamic forces, optimizing flight efficiency under varying conditions. For example, self-healing materials enable autonomous or stimuli-triggered repair of structural damage that can mitigate the effects of microcracks and fatigue-induced damage, extending the lifespan of critical components and reducing maintenance costs [18; 19].