Influence of flexure–torsion coupling on wave propagation in 2D thin-walled lattice

Wave propagation behavior of 2D lattices has been analyzed using frame elements; however, the influence of flexure–torsion coupling on wave propagation in periodic lattice structures with thin-walled members remains unexplored. This study focuses on simple square lattice architectures composed of thin-walled mono-symmetric beams with varying flange widths and orientation angles of cross-sectional members. Both in-plane and out-of-plane wave responses are analyzed to capture a comprehensive understanding of wave dispersion. Each lattice is modeled using a unit cell approach, where individual members are represented as thin-walled beams. Spectral element method is employed to capture the wave propagation behavior of the lattices. By applying Bloch–Floquet boundary conditions, periodicity in the structure is enforced, thereby evaluating the dispersion surfaces, isofrequency contours, group velocity maps, and directivity plots elucidate the wave propagation characteristics of the lattices. Our findings reveal that the thin-walled lattice with flexural–torsional coupling produces blind zones in wave propagation, while the simple lattice exhibits uniform directivity and group velocity distribution. The analysis reveals critical insights into the energy flow and directionality of waves, providing a deeper understanding of the spatial and wavenumber-dependent behavior of flexure–torsion-coupled lattice structures. These findings offer significant implications for the design and optimization of advanced lattice materials and wave-based engineering applications.