An Adhesive-Free Integrated Sound Absorption and Insulation Structure Based on Light-Weight Three-Dimensional Graphene Oxide/Melamine Sponge

Integrated sound absorption and sound insulation materials (SAM-SIM) are widely used for noise control. While adhesive bonding is commonly employed to fabricate SAM-SIM composites, this approach carries inherent risks of interfacial failure. To enhance structural stability, a method combining vacuum impregnation and polymer curing at the bottom of porous sound-absorbing materials is proposed to obtain a double-layer SAM-SIM structure. In this study, graphene oxide (GO) modified melamine (MA) sponge synthesized by freeze drying served dual roles: as the SAM layer and as a component in the SIM layer. High-damping polyurethane (PU) was used as the polymer matrix in the SIM layer. GO content in the MA sponge and PU composites was modulated by adjusting the GO solution concentration. Sound absorption performance of GO/MA, as well as mechanical, damping and sound insulation performance of GO/MA/PU were studied systematically. Results indicate that GO improved the sound absorption performance of GO/MA and significantly improved the damping properties of GO/MA/PU composites. The double-layer structure with 12.5 mm thickness of SAM and 2.5 mm thickness of SIM derived from GO/MA composite sponge treated with 5 mg/mL GO solution possessed average sound absorption coefficient (SAC) of 0.547 and average transmission loss (TL) of 41.88 dB in the frequency range from 1000 to 6300 Hz. These values align closely with adhesive-bonded SAM-SIM with the same material system, demonstrating that vacuum impregnation of elastomers in porous SAM offers a viable alternative for developing stable SAM-SIM composites.