## 1 Introduction
Additionally, the performance of the lattice structure and the damping materials cannot be decoupled, complicating theoretical analysis and hindering the replacement of damping materials after failure. Furthermore, the aforementioned research primarily focused on vibration damping, aiming to enhance damping performance while maintaining a relatively high natural frequency, with the frequency range of interest being below the natural frequency of the lattice structure [28]. However, the vibration isolation performance of the composite structure has not been investigated. To enhance the damping performance and shock resistance of lattice structures, several studies have been conducted. The damping performance of lattice structures was enhanced by applying a polyurea coating to the surfaces of beams with a negative Poisson's ratio lattice and the energy absorption characteristics of the composite structure under shock loading were analyzed [14]. However, this damping method makes it difficult to control the coating thickness for optimal damping performance and does not decouple the performance of the lattice structure and the damping material, complicating theoretical analysis. Additionally, its focus is primarily on preventing structural damage. A composite polyurea foam was proposed, which was created by infiltrating polyurea foam into a lattice structure made of polyurea. Stress-strain characteristics, energy absorption, and cushioning efficiency were analyzed by quasi-static and dynamic strain rate experiments [29]. However, the aforementioned studies primarily focused on energy absorption and did not investigate vibration transmission under shock loading. In summary, existing studies have predominantly examined the vibration damping and energy absorption properties of composite structures while largely neglecting their vibration transmission behavior under vibration and shock loading conditions. Furthermore, the potential for enhancing their vibration isolation and shock resistance capabilities remains unexplored. This study focuses on vibration isolation and shock resistance for large power equipment operating in extreme environments, such as those involving strong radiation and severe corrosion. A parallel polyurea method for enhancing the damping characteristics of metal lattice structures is proposed, which utilizes the metal lattice structure to achieve a large load-bearing capacity and leverages the parallel polyurea's viscoelastic properties to improve the system's damping performance. The dynamic properties of polyurea materials are investigated, and a metal lattice-polyurea parallel composite vibration isolation system is designed. A theoretical model of the composite system is established, followed by a theoretical analysis of its damping performance, shock resistance, and vibration isolation effectiveness. The analytical results are subsequently validated through semi-sinusoidal shock and swept-frequency experiments. The rest of this paper is structured as follows: Section 2 introduces the metal lattice-polyurea parallel composite structure and presents the theoretical modeling of the corresponding composite vibration isolation system. Section 3 outlines the experimental methodology, including dynamic mechanical property tests of polyurea materials and shock and swept-frequency excitation tests of the metal lattice-polyurea parallel composite vibration isolation system. Section 4 is the results and discussion. Section 5 is the conclusion of the paper.