On the use of the combined FMC-ASED criterion for fracture prediction of notched specimens with nonlinear behavior

Abstract

ABSTRACT: The Averaged Strain Energy Density (ASED) criterion has been widely used for the prediction of fracture conditions in a number of materials containing notch type defects, similarly to other well-known methodologies such as the Theory of Critical Distances (TCD). This criterion is linear-elastic, so the results obtained in linear-elastic materials have been accurate. However, as soon as the material behavior becomes nonlinear, the resulting accuracy decreases. With the aim of using linear-elastic simple methods (such as the ASED criterion) in nonlinear materials, several attempts have been made to convert a physically nonlinear behavior into an equivalent linear behavior. Thus, when the tensile behavior in plain specimens reveals nonlinearity, but the fracture behavior in the presence of defects is linear, the Equivalent Material Concept (EMC) has been successfully validated (EMC-ASED criterion). However, there are situations in which the nonlinear behavior takes place in both tensile and fracture behaviors, and the EMC-ASED criterion loses accuracy and requires further evolution. At this point, the Fictitious Material Concept allows the analysis of nonlinear materials (at both tensile and fracture conditions) to be performed with significant accuracy. In this context, this article provides the prediction of fracture loads in single edge notched bending (SENB) specimens made of short glass fiber reinforced polyamide 6 (SGFR-PA6, 10 wt.%) containing U-notches and different levels of moisture content. The predictions are obtained through the combination of the FMC and the ASED criterion (FMC-ASED combined criterion). The results are significantly more accurate than those obtained through the ASED and the EMC-ASED criteria, but less accurate than those used when combining the FMC with the TCD.