Numerical determination of the strain energy release rate, comparison with the J-Integral and use of methods for calculating the effective crack length in mode I fracture mechanics experiments

• Κύριος συγγραφέας: Ζουμπουρλός, Αρσένιος-Στέφανος
• Άλλοι συγγραφείς: Zoumpourlos, Arsenios-Stefanos
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Composite materials; Fracture mechanics; Effective crack length; Secondary cracks; Cohesive Zone Model (CZM); Virtual Crack Closure Technique (VCCT); J-integral; Σύνθετα υλικά; Θραυστομηχανική; Ισοδύναμο μήκος ρωγμής; Δευτερεύουσες ρωγμές

In this work, a numerical investigation of the fracture behavior of two different adhesive joints is done using finite element methods for delamination assessment under pure mode I loading. The first joint is a dissimilar and unbalanced adhesive joint between thin titanium and CFRP adherents, that is destined for application in the future aircraft’s leading edge. This joint is reinforced from both sides with two aluminum beams to increase its flexural stiffness. For this joint, both two-dimensional and three-dimensional finite element analyses were performed due to its complexity. The second is a similar and balanced one and consists of two UD-CFRP sub-laminates which are being co-cured with the adhesive film to conclude to the final joint under study. Only two-dimensional finite element analyses were performed for this joint due to its symmetry. The finite element analyses made using cohesive zone modeling, virtual crack closure technique and contour integral analysis to capture the fracture behavior of these joints under pure mode I loading. A comparison of the different effective crack lengths calculated by various analytical equations for the compliance from the literature, is made for each joint. The calculation of the effective crack length is very useful in cases where it is not possible to measure the crack length during propagation, such as mode II experiments, or in cases where secondary cracks appear, as in the case of TiCoAJo. In addition, with the effective crack length concept it is accounted the fracture process zone effects. Also, a comparison between J-Integral and strain energy release rate calculated by different methods, is made for each joint. Finally, the results of the finite element analyses are validated with the experimental results.