Broadening the Vibration Attenuation of Locally Resonant Metamaterials Using Multimaterial Injection Molding

Abstract Lightweight materials and design, though economically and ecologically attractive, typically suffer from poor vibro-acoustic performance, for which locally resonant metamaterials have recently emerged as promising solutions. They enable stop bands, targeted frequency zones of strong vibration attenuation, through subwavelength integration of resonant inclusions to a host structure. However, their limited broadband performance and lack of mass-manufacturing methods currently hinder industrial adoption. Injection molding is therefore gaining attention as a viable manufacturing process. To transition toward mass-manufacturable metamaterials with broadband-enhanced vibration attenuation, this work investigates how advanced multimaterial injection molding strategies may be leveraged. In particular, a design methodology is introduced for multimaterial resonant inclusions where mass is efficiently added via small inserts and overmolding to tune the targeted frequency bands, while highly damped material is strategically applied to widen and even merge stop bands. Specifically, acrylonitrile-butadiene-styrene (ABS) provides strength and stiffness, and thermoplastic polyurethane (TPU) increases material damping. First, the influence of different ABS–TPU distributions and interfaces on the bond strength and resulting stiffness and damping is investigated. The outcomes reveal how material layout may be best leveraged in resonator design for broadband performance. Next, the parametrized ABS–TPU layout within the resonator is optimized to enhance broadband vibration attenuation. Small masses are included to tune the resonance frequencies. Vibration measurements on the manufactured metamaterial plate with optimized multimaterial resonator additions confirm broadened vibration attenuation, demonstrating the potential of multimaterial injection molding for mass-manufacturing of locally resonant metamaterials with broadband-enhanced performance.