To predict durability of polymeric structures an information on polymers long-term properties in the form of relaxation modulus and/or creep compliance is required. It iswell known that determination of relaxation or creep properties from experimental data isan inverse problem, which, due to presence of experimental errors in input data, becomesill-posed. To find a stable solution using standard integration schemes is practically impos-sible. In this paper we propose a hands-on methodology which bypasses the solution ofill-posed integral equation and allows finding long-term relaxation or creep properties fromsimple constant strain rate or constant stress-rate experiments performed at different temper-atures. The proposed approach can be applied not only for characterization of viscoelasticmaterials in solid state but can also be used for prediction of time-dependent properties ofpolymer melts. The paper presents the detailed steps of the proposed method as well as itsvalidation on several simulated and real experimental data. It has been shown that the pro-posed approach can accurately reconstruct the desired long-term time-dependent propertiesobtained in traditional way (i.e., from step loading).
COBISS.SI-ID: 13309211
This chapter in the Encyclopedia of Thermal Stresses provides an overview on experimental approaches commonly used to determine the thermal and the time-dependent mechanical properties in shear and bulk of materials along with the numerical procedures for obtaining the unique master curve of the selected material function. Proper characterization of the time-dependent properties in shear and bulk is necessary for reliable prediction of mechanical response of the material in linear viscoelastic domain as well as in the non-linear viscoelastic domain.
This paper describes a novel apparatus for measuring dynamic bulk compliance B*(ω) of time-dependant materials. System can measure dynamic bulk compliance at room temperature, at pressures up to 100 ± 1,5 bar and frequencies from 100 Hz to 1000 Hz. Functionality of the apparatus is demonstrated by performing measurements of dynamic bulk compliance for two different materials, i.e., polyvinyl acetate (PVAc) and thermoplastic polyurethane (TPU). Measurements were conducted at room temperature, atmospheric pressure and frequencies from 100 Hz to 1000 Hz.
COBISS.SI-ID: 13363739