A comprehensive review on in-plane and through-the-thickness auxeticity in composite laminates for structural applications.

Auxetic laminates are part of a fascinating branch of materials denominated as auxetics, which display a NPR (Negative Poisson's Ratio), an uncommon property in the engineering world. Auxeticity is at the root of enhancements in shear and indentation resistance, fracture toughness and energy absorption, making the design of NPR a desirable feat in structural engineering. In composite laminates made of conventional, i.e. positive Poissons ratio, materials, auxeticity is a result of the combination between particular angular configurations and anisotropic materials. Such laminates can be used in a wide array of engineering applications, especially those which require high energy absorption capacity, including aerospace, personal defense and sports industries. This review focuses on particular property enhancements reported in the scientific world brought about by the design and application of IP (In-plane) and TTT (Through-the-thickness) NPR fibre-reinforced polymer laminates under QSI (Quasi-static indentation), LVI (Low-velocity impact) and fatigue solicitations. Furthermore, some insight is given on some possible future paths for further investigation of this topic. [ABSTRACT FROM AUTHOR]