Objective To address the trade-off between lightweight design and low-noise performance in composite unmanned surface vehicles (USVs) structures and to enhance the hull's underwater acoustic stealth capability, this study systematically investigates the acoustic radiation characteristics and thickness optimization of composite sandwich structures used in USVs.

Methods Based on vibro-acoustic coupling theory, a finite element acoustic model of a USV sandwich structure composed of glass fiber-reinforced polymer (GFRP) skins and a PVC foam core is established to numerically predict underwater acoustic radiation in the frequency range of 10–50 Hz. Parametric analyses are performed to systematically examine the effects of variations in GFRP skin thickness and PVC core thickness on the acoustic radiation performance of the structure. On this basis, a bi-objective optimization model is developed with structural weight and total radiated sound pressure level (TRSPL) as the objectives. Gaussian Process Regression (GPR) is employed to construct a surrogate model describing the relationship between structural thickness parameters and acoustic response. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is integrated to perform multi-objective optimization, thereby obtaining the Pareto optimal solution set within the continuous thickness design space.

Results The results demonstrate that the acoustic radiation performance of the sandwich structure is sensitive to variations in both skin and core thickness. The PVC foam core thickness plays a dominant role in improving acoustic performance, whereas the GFRP skin thickness varies within a relatively narrow range once structural requirements are satisfied. The Pareto front obtained from multi-objective optimization exhibits a clear characteristic of diminishing marginal returns. Based on an analysis of the Pareto solution set, three representative thickness-matching schemes are identified: lightweight, performance-balanced, and enhanced noise-reduction configurations. For instance, the performance-balanced scheme, with a skin thickness of approximately 3–4 mm and a core thickness of approximately 10–18 mm, can achieve a reduction of approximately 3–5 dB in the total radiated sound pressure level while maintaining a controllable structural weight.

Conclusions The proposed analysis and optimization approach provides a quantitative engineering reference for the low-noise design of composite sandwich structures in USVs.