PSI - Issue 28

S. Cicero et al. / Procedia Structural Integrity 28 (2020) 84–92 Cicero et al./ Structural Integrity Procedia 00 (2019) 000–000 fracture toughness and the tensile strength of the fictitious material, respectively, and calculate the values of the control volume radius ( � ��� ) and the critical SED ( �� ��� ) by using Eqs. (5) and (6). The values of the control volume radius and the critical SED for the SGFR-PA6 materials with two different moisture contents are presented in Section 3. � �� � ��� � � (5) � � � (6) 3. Results and discussion 3.1. Tensile tests The main parameters obtained from the tensile tests are shown in Table 1 (Ibáñez-Gutiérrez et al. (2019)), whereas Figure 3 shows the corresponding strain-stress curves. One of the tests performed with 2% moisture content was not valid and it is not included in the results. It can be observed how the higher the moisture content the lower both the proof stress and the ultimate tensile strength, and the higher the strain under maximum load. Table 1. Tensile parameters for the different levels of moisture content. E: elastic modulus; σ 0.2 : proof stress; σ u : engineering ultimate tensile strength; e max : engineering strain under maximum load. Moisture content E (GPa) σ 0.2 (MPa) σ u (MPa) e max (%) 2% 2.0 31.0 63.4 18.6 5% 0.95 22.5 47.7 22.7 89 6

Fig. 3. Tensile curves obtained for the different levels of moisture content

3.2. Fracture tests Figure 4 shows a couple of the load-displacement curves obtained in cracked specimens, which are also used to calibrate the FMC. The clear nonlinear behavior of the specimens containing 5% of moisture can be observed. This