[Zurück]


Wissenschaftliche Berichte:

C. Cheyrou, H. E. Pettermann:
"FEM Simulation of the Thermo-Viscoelastic Behaviour of Composites";
Bericht für Institut für Leichtbau und Struktur-Biomechanik, TU Wien; Berichts-Nr. ILSB-Report 298, 2016; 49 S.



Kurzfassung englisch:
Thermo-viscoelastic composites are widely used in the industry and show time-dependent behaviors. In order to conduct analyses on structures made of such type of materials, a mathematical model has been developed by Pr. Pettermann at the ILSB and implemented in an FEM program. The model requires as inputs the dynamic physical properties of the thermo-viscoelastic composite constituting
the structure.

One of the focuses of the current research project is the conduction of structural analyses with the Institute´s program. The specific case of linear fiber-reinforced thermo-viscoelastic transversely isotropic composites is chosen. All studies are carried out in the time domain. At first, the required material data are obtained thanks to unit cell simulations with a commercial package. In the case of an homogeneous viscoelastic matrix and elastic glass fibers, the appropriate load cases and boundary conditions provide relaxation curves from which the material data are extracted and calibrated. These data are used as input to the Institute´s constitutive law to study the characteristics of a laminated material. The response of different laminated shells to external forces and temperature changes are observed. The structures with external fibers loaded in their length direction are proven to resist better to bending. The deformed shape depend on the orientation of the different layers of fibers. This study can be done for any viscoelastic composite structure, and the resulting observations are to be used as preliminary behavior prediction before real composite usage.

Temperature dependence of relaxation elements for different types of viscoelastic composites is then studied, with the objective to later implement an efficient temperature dependence of composites in the Institute´s subroutines. Temperature-shift functions of the WLF type, usually used for pure polymers, are here searched for the relaxation elements of different viscoelastic fiber-reinforced composites. Finding these functions (if they exist) enables to deduce the material behavior at any temperature if it is known at one temperature, thanks to a time rescaling. In some simple cases, when only one temperature-dependence behavior is present in the constituents of the composite, a single WLF function works for all the relaxation elements. However, for more complicated composites, each relaxation element has its own shift function which is valid for a restricted range of temperatures. Therefore, the implementation of the temperature dependence in the Institute´s subroutines should take into account the possibility of different shift functions for each relaxation element, as well as the temperature range for which these functions are valid.

Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.