Simple constitutive methods to represent the tensile response of a laboratory-aged nonwoven geotextile

Simple constitutive models (polynomial and hyperbolic-based) were used to represent the tensile response of a nonwoven polypropylene geotextile. The model parameters were defined for a virgin sample and for samples submitted to two degradation mechanisms: thermo-oxidation and artificial weathering. Thermo-oxidation tests were carried out by the oven-ageing method (exposure in air, 110 ºC, in the dark during 56 and 112 days). The artificial weathering tests were performed in a laboratory weatherometer with exposure to ultraviolet radiation and water spraying. The virgin and laboratory-aged samples were characterised by tensile tests. The laboratory-aged samples exhibited some changes in their tensile properties. The best constitutive model to approximate the response of the geotextile (virgin and laboratory-aged samples) was the polynomial (order 6). However, the model parameters have no physical meaning. The hyperbolic-based model fitted well the experimental data. Model parameters a and b have physical meaning as they were related to tensile properties. The fit improved by using correction factors. Hyperbolic-based model parameters for the laboratory-aged samples were adequately estimated from tensile properties of the virgin sample and reduction factors for the laboratory ageing induced. This latter approach for estimating model of aged samples is promising and should be explored further.