Sound-absorbing coatings with nonlinear elastic modulus

Area of Science:

• Acoustics
• Materials Science
• Nonlinear Dynamics

Background:

• Cavity-type anechoic coatings are crucial for underwater acoustic management.
• Existing linear models struggle to accurately predict sound absorption under varying conditions.
• Material nonlinearity in coatings significantly impacts acoustic performance.

Purpose of the Study:

• To develop and validate a nonlinear model for cavity-type underwater anechoic coatings.
• To investigate the influence of acoustic frequency and incident sound pressure on coating performance.
• To enhance the prediction accuracy of sound absorption coefficients.

Main Methods:

• Utilized a complex Young's modulus dependent on acoustic frequency and sound pressure.
• Employed the Kraus model to represent the nonlinear modulus, fitting Dynamic Mechanical Analysis data.
• Implemented the Newton-Raphson method for iterative absorption calculations.
• Validated against analytical solutions (transfer matrix method) and experimental data.

Main Results:

• The nonlinear model accurately predicts enhanced and shifted resonance peaks compared to linear models.
• Model predictions show good agreement with experimental sound absorption data.
• Reduced prediction errors for peak frequencies by 33.0% to 55.9% compared to linear models.
• Demonstrated that acoustic frequency and incident sound pressure influence cavity resonance through the nonlinear modulus.

Conclusions:

• Material nonlinearity is essential for accurate modeling of underwater anechoic coatings.
• The proposed nonlinear model significantly improves prediction accuracy over linear approaches.
• The findings offer a more reliable tool for designing advanced underwater acoustic materials.