The convergence of carbon nanomaterials and functional polymers has led to the emergence of smart carbon–polymer nanocomposites (CPNCs), which possess exceptional potential for next-generation sensing and actuation systems. These hybrid materials exhibit unique combinations of electrical, thermal, and mechanical properties, along with tunable responsiveness to external stimuli such as strain, pressure, temperature, light, and chemical environments. This review provides a comprehensive overview of recent advances in the design and synthesis of CPNCs, focusing on their application in multifunctional sensors and actuator technologies. Key carbon nanomaterials including graphene, carbon nanotubes (CNTs), and MXenes were examined in the context of their integration into polymer matrices to enhance performance parameters such as sensitivity, flexibility, response time, and durability. The review also highlights novel fabrication techniques, such as 3D printing, self-assembly, and in situ polymerization, that are driving innovation in device architectures. Applications in wearable electronics, soft robotics, biomedical diagnostics, and environmental monitoring are discussed to illustrate the transformative impact of CPNCs. Finally, this review addresses current challenges and outlines future research directions toward scalable manufacturing, environmental stability, and multifunctional integration for the real-world deployment of smart sensing and actuation systems.

Polymer composites have opened a novel innovation phase in additive manufacturing (AM), and now lightweight, high-strength, and geometrical advanced components with tailored functionalities can be produced. The present study introduces advances in polymer composite materials and their integration into AM processes, particularly in rapidly growing industries such as aerospace, automotive, biomedical, and electronics. The embedding of cutting-edge reinforcement materials, such as nanoparticles, carbon fibers, and natural fibers, into polymer matrices enhances mechanical, thermal, electrical, and multifunctional properties. These material developments are combined with advanced fabrication techniques, including multi-material printing, in situ curing, and functionally graded manufacturing, which achieves accurate regulation of microstructures and properties. Furthermore, high-impact innovations such as smart polymer composites with self-healing or stimuli-responsive behaviors, the growing shift toward sustainable, bio-based composite alternatives, are driving progress. Despite significant advances, challenges remain in interfacial bonding, printability, process repeatability, and long-term durability. This review offers a comprehensive overview of current advancements and outlines future directions in polymer composite–based AM.

The aviation industry is a major source of greenhouse‐gas emissions and faces urgent pressure to transition to sustainable energy solutions. In this context, hydrogen energy emerges as a promising alternative to conventional jet fuels, offering the potential for zero in‐flight CO ₂ emissions. This paper critically reviews hydrogen's role in aviation, covering production methods, propulsion technologies (fuel cells and hydrogen combustion engines), and cryogenic‐storage systems. Key challenges are identified, including infrastructure development, storage complexity, safety, regulatory barriers, and economic viability. Notably, adopting liquid hydrogen is projected to increase direct operating costs by 10%–70% for short‐range and 15%–102% for medium‐range flights, mainly due to storage and supply‐chain demands. Moreover, persistent issues such as contrail formation and NO _X emissions require further attention. Despite these hurdles, hydrogen offers promising decarbonization potential through diverse propulsion pathways, including direct combustion, fuel‐cell systems, and hybrid configurations. The paper proposes a phased integration roadmap: near‐term adoption in regional aircraft, mid‐term retrofitting of existing fleets, and long‐term sector‐wide decarbonization by 2050. Coordinated policy, sustained investment, and industry‐wide collaboration are essential to overcome barriers and accelerate aviation's clean energy transition.