PSI - Issue 51

Hugo Vidinha et al. / Procedia Structural Integrity 51 (2023) 9–16 H. Vidinha et al./ Structural Integrity Procedia 00 (2019) 000–000

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and with a displacement rate of 2 mm/min. The strain fields at the specimen surface were obtained using Digital Image Correlation (DIC) using a VIC-3D system. The numerical procedure was conducted using explicit quasi-static analysis. A three-dimensional mesh created using 8-node linear hexahedral elements with reduced integration (C3D8R) was used. The assembled model had 123,262 elements and 146,874 nodes. An overview of the mesh topology near the hole region can be seen in Fig. 2(b). A mesh sensitivity analysis, based on the convergence of the ultimate stress, was carried out to refine the mesh in the hole region. The mesh was highly refined near the geometric discontinuity to better simulate the strain fields around the geometric discontinuity. In remote regions, the mesh density was reduced to reduce the computational effort. The initial failure was verified via the Puck’s failure criterion while the progressive failure damage was analyzed using the Element Weakening Method (Lee et al., 2015; Vidinha et al., 2022).

Fig. 1. Specimen geometry used in the monotonic tensile stress-strain tests.

3. Puck’s failure criterion Puck’s failure criterion considers transverse isotopic lamina and distinguishes two types of fracture: Fibre Fracture (FF) and Inter Fibre Fracture (IFF). All material properties used in Puck’s failure criterion are transversely isotropic lamina properties, except in some cases which will be indicated in the text. 3.1. Fibre fracture Fibre fracture is mainly caused by stresses in the fibre direction and its condition can be written as follows: � 1 ‖ ��� � � �� ⏊‖ � ⏊‖� � � ‖ ‖� �� � � � �� ������������������������� � 1 (1) with � ‖ � � � � ‖ � � � (2) where ‖ � is the fibre parallel tensile strength, ‖ � is the fibre parallel compressive strength, ⏊‖ is the major Poisson’s ratio of the fibre, ‖ is the longitudinal modulus parallel to the fibers, while ‖� is the fibre longitudinal modulus. Also, � � is the magnification factor for the transverse stress in the direction of the fibre. In this work, � � was set to 1.3. 3.2. Inter fibre fracture Regarding the Inter Fibre Fracture (IFF), the Cauchy stress tensor is adapted creating a new coordinate system that allows the analysis of the IFF from an inclined fracture plane defined by