Experimental determination of the strain energy release rate, comparison with the j-integral and use of methods for calculating the effective crack length

• Κύριος συγγραφέας: Δημόπουλος, Γεώργιος
• Άλλοι συγγραφείς: Dimopoulos, Georgios
• Γλώσσα: English
• Έκδοση: 2023
• Θέματα: Fracture mechanics; Composite materials; Effective crack length; SERR; J-integral; Θραυστομηχανική; Σύνθετα υλικά; Ισοδύναμο μήκος ρωγμής; Ρυθμός απελευθέρωσης ενέργειας παραμόρφωσης

In this work, an investigation of the fracture behavior of two different adhesive joints is carried out using experiments to evaluate the interfacial delamination under Mode I loading. The two joints utilized are the dissimilar Titanium-CFRP joint, which consisted of a Titanium sheet bonded to a plate of multilayer CFRP material. This joint was reinforced on both sides with two Aluminum beams to increase the stiffness of the joint and prevent plastic deformation of the Titanium. The second joint is symmetrical and consists of two UD-CFRP plates which have been polymerized together with the adhesive film to create the final joint investigated. Static experiments were carried out to obtain results for the fracture resistance of the joints. By calibrating the compliance-crack length curve from the experiments and through analytical equations from literature, various equivalent crack lengths were calculated. The advantages of deriving equivalent crack length are significant as many times visual observation of the crack during propagation is difficult or even impossible. Such cases are the experiments with Mode II loading, where the two bonded sublaminates do not open and the existence of a secondary crack in the specimen where it is not easy to separate the primary and secondary crack, as is the case in the TiCoAJo. The last advantage of the equivalent crack length is that any existence of plastic deformation "in front" of the apparent crack can be accounted for the calculations. Finally, subject of the thesis is also the comparison of the Strain Energy Release Rate (SERR) obtained from the equivalent crack lengths with the J-Integral calculated through video recording of the experiments.