Characterisation of an Elastomer for Noise and Vibration Insulation in Lightweight Timber Buildings

Abstract

Regulations regarding impact and airborne sound insulation for lightweight timber constructions have become increasingly stringent due in particular to complaints by inhabitants. Accordingly, some building techniques frequently use elastomers at junctions so as to reduce low frequency noise. Development of accurate predictive tools (involving exact material properties) by using numerical methods such as the finite element (FE) method is needed in tackling flanking transmission problems during the design phase of buildings. The present research concerns the characterisation of an elastomer, presenting an accurate method for extracting its material properties from the manufacturer's data sheet (properties there being often linked to such structural effects as shape factors and boundary conditions of samples and tests). The properties were extracted by comparing results obtained by analytical calculations, FE simulations, and mechanical testing, separating geometry and material dependence and ultimately serving as input to commercial FE software for setting up the aforementioned prediction tools.

A high-order finite element model for vibration analysis of cross-laminated timber assemblies

“…The complex displacement amplitudes  d under a certain harmonic load which is characterized by the amplitude  F and angular frequency Ω are calculated from equation (16). Similar to equation (13), it is derived from equation (2).…”

“…Similar to equation (13), it is derived from equation (2). In equation (16), damping is taken into account by assembling complex element stiffness matrices to the system matrix 22,32 :…”

“…27 Since the obstruction of transverse deformations at the top and bottom of the elastomer specimen is not taken into account, these values should not be used for modeling an elastomer with volumetric finite elements. Therefore, a method to determine appropriate values of the dynamic Young’s modulus E el dyn and the Poisson’s ratio ν el of an elastomer is shown in Negreira et al 16 The values of E el dyn and ν el were identified therein by the example of Sylodyn® NE 28 as follows: First, the static Young’s modulus E el stat was determined from a compression test with lubricated plates, in which transverse deformations are not constrained. Secondly, the Poisson’s ratio ν el was detected by recalculating the compression test with non-lubricated plates using a finite element software.…”

“…Alternatively, elastomers can be modeled by volumetric finite elements. Their frequency-dependent material properties can be derived from the data sheet of the elastomer by a method which is described in Negreira et al 16 By comparing the calculated natural frequencies and the vibrations of an exemplary CLT assembly to measurement results from Mecking et al, 17 this article demonstrates that material values determined according to Negreira et al 16 are also suitable for the representation of a junction that includes not only the elastomer but also screws. If the static Young's modulus of the elastomer is not known from an additional measurement, non-unique material values of the elastomer are found.…”

“…Alternatively, elastomers can be modeled by volumetric finite elements. Their frequency-dependent material properties can be derived from the data sheet of the elastomer by a method which is described in Negreira et al 16…”