The weak stiffness and strength of materials with negative Poisson’s ratio limits their application. In this paper, three types of novel lattices with negative Poisson’s ratio are proposed to improve not only stiffness and strength but also energy absorption capacity by embedding different ribs into a classic re-entrant structure. Unit cell analyses show these novel lattices have significantly increased Young’s modulus along the loading direction, and Type C can maintain sufficient negative Poisson’s ratio performance compared with the base lattice. In addition, the novel lattices exhibit higher yield stress, plateau stress and densification strain extracted from quasi-static compressive simulation. The lattices are prototyped by laser-based additive manufacturing and tested in quasi-static experiments, which show the experimental data match the numerical results within an error of margin. The work signifies the prospect of lattices with negative Poisson’s ratio in enhancing engineering-applicable structures, and indicates the potential of structural topology optimization in more sophisticated designs.

As a new approach to passive noise control in low frequency domain, the targeted energy transfer (TET) technique has been applied to the 3D fields of acoustics. The nonlinear membrane absorber based on the TET can reduce the low frequency noise inside the 3D acoustic cavity. The TET phenomenon inside the 3D acoustic cavity has firstly investigated by a two degrees-of-freedom (DOF) system, which is comprised by an acoustic mode and a nonlinear membrane without the pre-stress. In order to control the low frequency broadband noise inside 3D acoustic cavity and consider the influence of the pre-stress for the TET, a general model of the system with several acoustic modes of 3D acoustic cavity and one nonlinear membrane is built and studied in this paper. By using the harmonic balance method and the numerical method, the nonlinear normal modes and the forced responses are analyzed. Meanwhile, the influence of the pre-stress of the nonlinear membrane for the TET is investigated. The desired working zones of the nonlinear membrane absorber for the broadband noise are investigated. It can be helpful to design the nonlinear membrane according the dimension of 3D acoustic cavity to control the low frequency broadband noise.

The targeted energy transfer (TET) technique could be applied to reduce the low frequency noise by a nonlinear membrane absorber as nonlinear energy sink (NES) inside a tube or an acoustic cavity. The pre-stress of the nonlinear membrane can affect the desired working zone for the TET and also the suppressed amplitude of noise. In order to design the nonlinear membrane according to a given acoustic medium, the influence of the pre-stress of the nonlinear membrane is quantitatively studied in this paper. The analytical formulae over the pre-stress of the membrane are established based on a general model of the system with an acoustic mode of 3D acoustic cavity and one membrane. Meanwhile, the suppressed frequency bandwidth of noise is investigated under different pre-stress levels of the membrane by using harmonic balance method and numerical method. For convenient applications, the radial deformation analysis and the modal analysis of the membrane with the pre-stress are finally performed by finite element method (FEM) to obtain the relationship between the radial displacement and the first mode. It can be helpful to guide design of the pre-stress of the membrane NES according to the desired working zone for the practice engineering application in acoustic field.