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The objective of this paper is to investigate the vibration isolation performance of an impact testing machine mounted on elastomeric nanocomposite mounts. An effective analytical-experimental test method was implemented in this paper to characterize the vibration isolation performance of acrylonitrile-butadiene rubber (NBR) mounts reinforced with multi-walled carbon nanotubes (MWCNTs). This method utilizes modal tests in order to measure experimental transfer functions (TFs) of a impact testing machine as a correlation parameter to analyticalexperimental determined TFs. The optimization procedure is carried out using a genetic algorithm (GA) by minimizing the difference between the experimental data from modal tests and the calculated response. A series of NBR mounts were manufactured with different concentrations of MWCNTs. The vibration isolation capacity of the machine mounts was determined through the transmissibility of a suitably designed test system. Elastomers' vibration isolation performance was ameliorated with the inclusion of MWCNTs, signifying that the enhancement of the elastomers with MWCNTs was rather effective. It is also shown that the stiffness of an elastomer and its damping capacity can be tuned by adjusting the proportion of MWCNTs. The vibration level of the impact-testing machine was decreased to 91% by incorporating the optimal concentration of MWCNTs in NBR mounts. [ABSTRACT FROM AUTHOR]

In the current paper, the modal characterisation of aramid–carbon fiber hybrid composites (ACFRP) and ACFRP reinforced with silica nanoparticles (nACFRP) is investigated through the analytical-experimental transfer function method. The modal properties, such as resonant frequencies and modal loss factors, are measured by vibrating cantilever beam specimens with an impact hammer, while the vibratory response is detected through an acceleration transducer. The procedure for the identification of analytical-experimental transfer functions is carried out using a genetic algorithm by minimising the difference between the measured response from tests and the calculated response, which is a function of the modal parameters. The analytical transfer functions provide a substructuring process to identify modes, as a function of damped natural frequencies and loss factors of a complex structure, and it is insensitive to experimental noise as well as the modal coupling effect. The validation of the proposed method is verified with 10 degrees of freedom mass-spring dashpot model. The effectiveness of the proposed method is demonstrated by investigating the static and dynamic behaviour of the ACFRP and nACFRP specimens. Results indicate that the inclusion of nanosilica particles increase the stiffness of the ACFRP, although the damping response of the reinforced specimens is moderately improved. [ABSTRACT FROM AUTHOR]

An efficient identification method for modal testing of viscoelastic composite materials is demonstrated in this paper, through the analytical–experimental transfer function method. The procedure for the identification of analytical–experimental transfer functions is carried out using a genetic algorithm (GA) by minimizing the difference between the measured response from tests and the calculated response, which is a function of the modal parameters. The analytical transfer functions provide a sub-structuring process to identify modes, as a function of damped natural frequencies and loss factors of a complex structure and it is insensitive to experimental noise as well as the modal coupling effect. The proposed method is verified with the calculation of the elastic modulus and modal properties of a cantilever steel beam with the FEM and compared with the identification results of the proposed algorithm. The effectiveness of the proposed method is demonstrated by investigating the static and dynamic behavior of epoxy cantilever beam specimens reinforced with silica nanoparticles. Analytical–experimental transfer functions accurately identified the viscoelastic and dynamic response of the studied specimens, while the results indicated that the inclusion of nanosilica particles increased the stiffness of the epoxy network and the damping response of the reinforced specimens is improved. [ABSTRACT FROM AUTHOR]