# An Overview of Smart Composites for the Aerospace Sector
## 4 Discussion
### Trends in Top Publications  
The most impactful publications indicated in Table 4 show four main trends that have guided research in recent years. These lines of development stand out for their focus on (i) electromagnetic interference (EMI) shielding, (ii) additive manufacturing of smart materials, (iii) piezoelectric materials and smart sensors, and (iv) aerogels and ultralight materials. The first trend responds to the growing demand for EMI shielding, driven by the expanding use of electronic devices in areas such as aviation, defense, and intelligent systems. In this context, various advanced material solutions have demonstrated their potential to enhance protection against electromagnetic interference. Here, carbon-based nanoparticles such as graphene, carbon nanotubes, and MXene have gained a great deal of attention. On the one hand, MXenes have emerged as promising alternatives to graphene for EMI applications due to their high electrical conductivity. A recent development has led to the creation of a flexible, hydrophobic, and lightweight MXene foam with a \begin{table}
\begin{tabular}{c c c c c} \hline
**Reference** & **Authors** & **TC** & **TC per Year** & **Normalized TC** \\ \hline
[26] & [PERSON] et al. & 1468 & 163.11 & 30.32 \\
[27] & [PERSON] et al. & 762 & 69.27 & 19.02 \\
[28] & [PERSON] et al. & 647 & 107.83 & 18.52 \\
[29] & [PERSON] et al. & 499 & 49.9 & 11.36 \\
[30] & [PERSON] et al. & 415 & 46.11 & 8.57 \\
[31] & [PERSON] et al. & 361 & 40.11 & 7.46 \\
[32] & [PERSON] et al. & 337 & 42.13 & 9.85 \\
[33] & [PERSON] el al. & 333 & 55.50 & 9.53 \\
[34] & [PERSON] et al. & 324 & 29.45 & 8.09 \\
[35] & [PERSON] et al. & 280 & 35 & 8.19 \\ \hline \end{tabular}
\end{table} 
Table 4: Top-cited publications by total and annual citations. \begin{table}
\begin{tabular}{c c c} \hline
**Country** & **TC** & **Average Article Citations** \\ \hline China & 17,761 & 28.10 \\ USA & 3313 & 23.80 \\ India & 2974 & 14.20 \\ Korea & 2316 & 23.90 \\ Italy & 2209 & 22.10 \\ Iran & 2111 & 20.90 \\ Canada & 1421 & 26.80 \\ \hline \end{tabular}
\end{table} 
Table 3: Most cited countries. shielding effectiveness of approximately 70 dB, surpassing the 53 dB of its non-foamed equivalents [26]. Another innovative approach involves the fabrication of MXene paper nanocomposites combined with silver nanowires, enabling the development of ultraflexible materials with an electrical conductivity of up to 3725.6 S-cm\({}^{-1}\) and an EMI effectiveness close to 80 dB [28]. On the other hand, hybrid nanocomposites such as hybrid silver-carbon foams have proven to be another effective solution with an EMI effectiveness of 70.1 dB and an extremely low density of 0.00382 g/cm\({}^{3}\), promoting flexibility, corrosion resistance, and high electron transport efficiency, making it ideal for aerospace applications and portable electronic devices [32]. Moreover, combining graphene with MXene has led to the creation of a hybrid foam with an EMI effectiveness of 50.7 dB and a shielding effectiveness per density ratio (SSE) of 6217 cm\({}^{3}\)/g [33]. The second trend is related to the additive manufacturing (3D and 4D printing) of smart materials. From one perspective, 3D printing using digital light processing has enabled the production of conductive nanocomposites, allowing the creation of hollow capacitive sensors, flexible circuits, and shape-memory materials for advanced electronics and sensing without compromising mechanical properties [31]. From another perspective, 4D printing enables new possibilities in soft robotics, flexible electronics, and minimally invasive medicine, with architectures that can transform between different configurations (e.g., 3D-1D-3D or 3D-2D-3D) using thermal or magnetic stimuli, expanding adaptive and dynamic system applications [30].