Optimising the mechanical characterisation of a resilient interlayer for the use in timber construction

Resilient interlayers are used in the field of building acoustics to reduce the transmission of vibrations through the flanking transmission paths. To this end, EPDM rubber or polyurethane strips are often used as dampers and therefore a complete mechanical characterisation for these materials is required. Most of the time, the mechanical characterisation has been related to the use as damping materials to be used in "standardised" application, such as industry. This paper reports the mechanical characterisation of an extruded polyurethane strip to be used in timber buildings. The mechanical characterisation of the strip was conducted according to standard tests (tensile, compression) on macro samples as well as using the DMA in tensile and shear mode, over a wide temperature range. The stress strain relation in compression was evaluated loading the sample with different boundary conditions in order to take into account the friction provided by different supports. Steel plates, timber lamellas and the "ideal" situation without friction were tested, pointing out the peculiar characteristics of the material when used as interlayer in CLT buildings. Considerations are made relative to the extraction of the E modulus over different ranges and related to the real on-site application of the loads that might render necessary an insight into the definition of the elastic properties of such materials.