Alternating layered design of rubber composites: Synergistic roles of damping loss factor and modulus in structural vibration control

Layered design is a well-established strategy for enhancing the damping performance of materials. However, most existing studies have primarily focused on increasing the loss factor through layered architectures, while overlooking the concomitant changes in modulus. In vibration control applications, the effectiveness of damping materials depends not only on the loss factor but also on the modulus, as both parameters jointly influence vibration attenuation. Due to interdisciplinary barriers, the coupled effects of dynamic mechanical properties in layered materials on the vibration performance of practical composite structures remain insufficiently understood. In this study, we address this knowledge gap through a combined experimental and numerical investigation. Alternating multilayered specimens (A/B-MLD) with varying numbers of layers and layer-thickness ratios were fabricated via hot-press lamination using two nitrile butadiene rubbers (NBR-A and NBR-B) as base materials, and their dynamic mechanical properties were systematically characterized. The influence of layer architecture on the viscoelastic behavior of the materials was then analyzed, revealing how structural design can be used to tailor damping and modulus. Finite element models of cantilevered beams and plates—under both free and constrained damping configurations—were developed to investigate the mechanisms by which dynamic mechanical properties affect structural damping and broadband vibration suppression. The results show that, in the constrained damping configuration, the composite loss factor of the 8-layer A/B-MLD increased by 23.1% and 9.2% compared to NBR-A and NBR-B, respectively. The alternating layered design enhanced energy dissipation at low frequencies through an increased loss factor, while higher modulus enabled effective vibration control at higher frequencies. As a result, the first two resonance peaks of the 8-layer A/B-MLD structure were reduced by 2.8 dB and 1.2 dB compared to NBR-B, with significant vibration attenuation observed across the 250–1000 Hz bandwidth.