Fiber reinforced composite laminates are increasingly replacing traditional metallic materials. The manufacturing process and service of the composite laminates frequently lead to delamination. Vibration analysis is an integral part of most engineering structures. In the present article we provide a relevant survey on the various analytical models and numerical analyses for the free vibration of delaminated composites. A basic understanding of the influence of the delamination on the natural frequencies and the mode shapes of composite laminates is presented. In addition, other factors affecting the vibration of the delaminated composites are discussed. Particular attention is given to composite laminates having piezoelectric sensors and actuators, and ones subjected to axial loadings.

Auxetic metamaterials attract wide attention due to their unusual mechanical behaviours. This work explores the tunability of the bidirectionally hyperbolic deformation of thin plates under uniaxial compression, instead of the Euler buckling deformation. Inspired by the horseshoe structures, through tuning the radius and thickness of the central circles of the horseshoes, as well as the thickness and subtending arc angles of the four branches, bidirectionally hyperbolic out of plane deformation was achieved together with auxetic behaviour. Finally, finite element simulations, theoretical analyses, and experimental verifications have been carried out to design the out of plane bidirectionally hyperbolic deformation by the tailorable temperature sensitivity and shape memory effect in unit cells.