Abstract
The development of new materials with reduced noise and vibration levels is an active area of research due to concerns in various aspects of environmental noise pollution and its effects on health. Excessive vibrations also reduce the service live of the structures and limit the fields of their utilization. In oscillations, the viscoelastic moduli of a material are complex and it is their loss part – the product of the stiffness part and loss tangent – that is commonly viewed as a figure of merit in noise and vibration damping applications. The stiffness modulus and loss tangent are usually mutually exclusive properties so it is a technological challenge to develop materials that simultaneously combine high stiffness and high loss. Here we achieve this rare balance of properties by filling a solid polymer matrix with rigid inorganic spheres coated by a sub-micron layer of a viscoelastic material with a high level of internal friction. We demonstrate that this combination can be experimentally realised and that the analytically predicted behaviour is closely reproduced, thereby escaping the often termed ‘Ashby’ limit for mechanical stiffness/damping trade-off and offering a new route for manufacturing advanced composite structures with markedly reduced noise and vibration levels.
Highlights
In a recent study entitled ‘Noise pollution: A modern plague’ Goines and Hagler[1] noted how noise pollution could have a significant impact on well-being and health and proposed a link between noise threshold and what they termed ‘displaced aggression’
(segmental) and side groups leads to viscoelasticity and high mechanical damping though leading to a low storage modulus
Hussein and Frazier[16] proposed periodic acoustic metamaterials which would show high levels of damping without sacrificing stiffness. This combination of high damping and high stiffness is the key aim of our work reported here, implemented in a polymer based composite material
Summary
In a recent study entitled ‘Noise pollution: A modern plague’ Goines and Hagler[1] noted how noise pollution could have a significant impact on well-being and health and proposed a link between noise threshold and what they termed ‘displaced aggression’. While there are a number of reported examples of materials that are able absorb sound waves, these normally involve designed meta-materials, with often complicated internal structures, which are not applied to most structures For this reason, in this work we have focussed our study on the second strategy, which is to rapidly decrease the amplitude of a vibrating structure. The loss modulus is the product of these two quantities and was considered by Chung, as a possible figure of merit for the ability of a material to reduce vibrations Another recent example is the work of Zhou et al.[12] who studied the damping properties of polyacrylate emulsion/hindered phenol hybrids. Hussein and Frazier[16] proposed periodic acoustic metamaterials (with local resonance properties) which would show high levels of damping without sacrificing stiffness
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