Functionally Graded Metamaterials (FGMMs) constitute an innovative class of materials within the realm of additive manufacturing (AM), attracting substantial attention from material science and research communities. These materials, characterized by unique designs and gradient properties, are not commonly found in nature but are deliberately engineered through the arrangement of subwavelength structures. The distinct attributes of such materials have propelled them into significant prominence across various industries, including automotive, aerospace, medical, electronics, and agriculture. This review paper aims to present a comprehensive overview of a range of techniques applied in the fabrication, design, theoretical models, and simulation methods related to these materials. It delves into the assessment of such material’s performance, specifically focusing on mechanical, thermal, and electromagnetic properties. Moreover, this review addresses advancements, challenges, and potential solutions in the field. Ultimately, it delivers valuable insights to researchers, practitioners, and stakeholders, enhancing their understanding of FGMMs and their significance in the broader context.

The present work deals with the study of active constrained layer damping treatment of multiscale carbon nanotube-based hybrid carbon fiber-reinforced composite plates. The distinctive feature of novel multiscale hybrid carbon fiber-reinforced composites is that the wavy/straight carbon nanotubes are distributed uniformly in the matrix phase of hybrid carbon fiber-reinforced composites, and the waviness of carbon nanotubes is considered to be coplanar with two mutually orthogonal planes. Firstly, the effective elastic properties of hybrid carbon fiber-reinforced composites are estimated using the Mori-Tanaka method. The outcomes of the Mori-Tanaka method suggest that the transverse effective elastic properties of hybrid carbon fiber-reinforced composites containing wavy carbon nanotubes are better than those of hybrid carbon fiber-reinforced composites with straight carbon nanotubes. Secondly, a finite element model using the layer-wise first-order shear deformation theory is developed to study the damping performance of hybrid carbon fiber-reinforced composite plates integrated with the active constrained layer damping treatment. The constraining layer of active constrained layer damping treatment is a 1–3 piezoelectric composite layer with vertically/obliquely-oriented piezo-fibers. The piezo-fibers make an angle [ ] with the vertical plane of a layer coplanar with the xz- or yz-plane. The effect of the orientation of piezo-fibers angle on the control authority of active constrained layer damping treatment patches is investigated. Our results reveal that the performance of multiscale hybrid carbon fiber-reinforced composite plates has improved due to the incorporation of wavy carbon nanotubes, and the orientation angle of piezo-fibers has a major impact on the control authority of active constrained layer damping patches. The proposed multiscale composite with the combination of wavy carbon nanotubes and active constrained layer damping patches can be actively used in the aerospace and transport industries to control the mechanical vibrations of structures.