Acoustic wave propagation through three-dimensional architected auxetic honeycomb-core cylindrical shells under external mean flow

The main purpose of this study is to explore the sound transmission loss (STL) performance of cylindrical shells incorporating a three-dimensional angle-graded auxetic honeycomb (3D AGAH) core, a specialized form of architected auxetic honeycomb structure, under external flow conditions. Initially, the structure is modeled using the state-space method, with the aid of 3D elasticity theory. In addition, the out-of-plane elastic characteristics of the 3D AGAH core are adopted. Subsequently, the STL is computed using appropriate boundary conditions, and the results showed excellent agreement with other studies. The study further examines the effects of shell curvature, incorporation of the 3D AGAH core, and external flow on the STL. It is found that increasing the Mach number (M = 0–0.5) leads to a higher STL across the 1–10 000 Hz frequency range, by modifying the pressure distribution and structural–acoustic interaction. Furthermore, this study analyzes how various factors affect the STL of sandwich cylindrical shells with 3D AGAH cores. Key findings indicate that at low frequencies, doubling the 3D AGAH core thickness results in an approximately 6 dB increase in the STL. Moreover, incorporating a 3D AGAH core with a lower mass than the aluminum structure enhances the STL of the cylindrical shell, particularly above the ring frequency, due to its greater thickness, which increases its flexural rigidity and rotational inertia. Consequently, the 3D AGAH core improves soundproofing performance while reducing the overall mass of the structure, making it particularly advantageous for mechanical applications where lightweight design and acoustic insulation are critical.