Novel multifunctional lattice composite structures with superior load-bearing capacities and radar absorption characteristics

Multifunctional composite structures have attracted increasing interest in design of ultra-lightweight for aerospace and marine applications. However, an optimized configuration together with precise theoretical prediction models still is urgently needed. In this work, a novel impedance-type square lattice composite structure (ISLCS) with superior out-of-plane load-bearing capacities and broadband radar absorption characteristics was designed. Two theoretical prediction models were developed for optimizing both mechanical and electromagnetic properties considering the shearing deformation of the Timoshenko beam and the scale effect of the electromagnetic wave frequency. The inherent effect mechanism between unit cell geometries and electromagnetic properties was firstly revealed. An integrated molding technology was adopted to fabricate a series of specimens composed of glass fiber reinforced polymer (GFRP) and resistance material. The reliabilities of the proposed models and simulations were verified by the out-of-plane compression and electromagnetic reflectivity tests. The optimized results revealed an average critical compressive stress of 40 MPa and an absorbing band of 5.4–18 GHz, consistent with the mechanical and electromagnetic simulations and experiments. Further simulations with different structural parameters confirmed the wide application scope and equivalence deduction between unit period and sheet resistance. In sum, this study provides a reference for future multi-objective optimization design of three-dimensional radar absorbing structures (3D-RASs).