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Strain rate dependent thermo-mechanical aspects of glass fiber reinforced thermoplastic based on experimental data

: Lienhard, J.; Huberth, F.


International Journal of Impact Engineering 131 (2019), pp.57-65
ISSN: 0734-743X
Journal Article
Fraunhofer IWM ()
field correlation; infrared measurement; LFRT; strain rate; thermo-mechanics

Thermo-mechanical material considerations have been published since two centuries. A new method of correlating experimental field information of strain and heat generate data for a physical based thermo-mechanical modeling of strain rate dependent material properties. Strain rate dependent characterizations under tensile loading of glass-fiber reinforced thermoplastic (LFRT) and its matrix material polypropylene (PP) were conducted. Higher fracture strains of LFRT with raising strain rate could be ascertained in contrast to the decreasing fracture strain of PP. High-speed video based digital image correlation (DIC) in combination with high-speed infra-red (IR) measurements provide field data of the deformation and the temperature evolution. A precise IR calibration method, the correlation of the Lagrangian deformation field with the Eulerian temperature field, the contemplation of volume specific values and the incorporation of the thermo-elasticity allowed the determination of the heat transition values with respect to strain and strain rate. The results show clear difference of (βdiff) between PP and LFRT. While PP shows a higher βdiff with rising strain rate and therefore higher energy dissipation, βdiff of LFRT decreases with the strain rate. The predominant role of thermo-elasticity was identified as the key-factor of higher energy absorption of LFRT at higher strain rates.