Characterisation by means of a finite element model of the influence of moisture content on the mechanical and fracture properties of the polyamide 6 reinforced with short glass fibre

This study involves the determination of the mechanical and fracture properties of polyamide 6 reinforced with short glass fibres (35 wt. %) at five different moisture contents (0, 1, 2, 3, and 6 wt. %, respectively). The mechanical characterisation consisted of tensile tests on plane specimens to determine the influence of moisture content on the material’s mechanical parameters. The study of fracture properties was carried out by performing single-edge notch bending tests on specimens with the levels of moisture mentioned above in order to obtain the critical stress intensity factor, KIc. The experimental results showed that the material fracture behaviour cannot be properly described following this methodology; for this reason, a more ambitious scope was established, consisting of determining the J-integral during stable propagation by combining the experimental force vs. displacement curves with the results of a finite element numerical model. The analysis clearly demonstrates the improvement in the material’s toughness as humidity increases.
The subsequent fractographic study performed through scanning electron microscopy allowed the influence of moisture content on the fracture micro-mechanisms developed during fracture and propagation to be determined.