PSI - Issue 72

A.F.L. Macedo et al. / Procedia Structural Integrity 72 (2025) 61–68

68

5. Conclusions This study investigated the t A influence on the mixed-mode fracture behavior of adhesive joints using CZM and the SLB test. The experimental data collected included P -  curves, R -curves, G I / G II ratios, and the fracture envelope. The P -  curves showed consistent results across equal t A batches. Crack propagation occurred with nearly constant G I and G II , although minor variations due to experimental factors were noted, with the highest variation (13.9%) in G II calculated via CBBM. The influence of adhesive thickness on G I / G II was significant, and fracture envelope analysis indicated that  =2 could accurately mod el the adhesive’s behavior. In the CZM analysis, numerical models reproduced experimental P -  behavior. Some deviations for t A =2.0 mm were attributed to FPZ effects. The CZM laws were consistent across different t A , with t n 0 and t s 0 increasing with t A , corresponding to the G I / G II increase. The fracture envelope successfully modelled  for smaller thicknesses, with slight variations for t A ≥1.0 mm. Parameter analysis indicated that G IC had the greatest impact on the mixed-mode behavior. References Antunes, R. P. R. O., Campilho, R. D. S. G., Silva, F. J. G., Vieira, A. L. N., 2021. Numerical validation of cohesive laws for adhesive layers with varying thickness in bonded structures. Procedia Manufacturing 55: 213-220 Davidson, P., Waas, A. M., Yerramalli, C. S., 2012. Experimental determination of validated, critical interfacial modes I and II energy release rates in a composite sandwich panel. Composite Structures 94(2): 477-483 Faneco, T. M. S., Campilho, R. D. S. G., Silva, F. J. G., Lopes, R. M., 2017. Strength and fracture characterization of a novel polyurethane adhesive for the automotive industry. Journal of Testing and Evaluation 45(2): 398-407 Fernández, M. V., de Moura, M. F. S. F., da Silva, L. F. M., Marques, A. T., 2013. Mixed-mode I + II fatigue/fracture characterization of composite bonded joints using the Single-Leg Bending test. Composites Part A: Applied Science and Manufacturing 44: 63-69 Irwin, G. R., Kies, J. A., 1954. Critical energy release rate analysis of fracture strength. Welding Journal 33: 193-198 Ji, G., Ouyang, Z., Li, G., 2012. On the interfacial constitutive laws of mixed mode fracture with various adhesive thicknesses. Mechanics of Materials 47: 24-32 Kim, W. S., Hwang, D. S., Jang, C. J., Lee, C. J. (2011). Enhancement of Composite-Metal Adhesion Strength by Micro-Patterning of Metal Surfaces. 18th International Conference On Composite Materials, Daejeon Lee, M. J., Lim, J. M., Lee, B. C., 2013. Finite Element Analysis of an Adhesive Joint Using the Cohesive Zone Model and Surface Pattern Design of Bonding Surfaces. The Journal of Adhesion 89(3): 205-224 Oliveira, J. J. G., Campilho, R. D. S. G., Silva, F. J. G., Marques, E. A. S., Machado, J. J. M., da Silva, L. F. M., 2020. Adhesive thickness effects on the mixed-mode fracture toughness of bonded joints. The Journal of Adhesion 96(1-4): 300-320 Oliveira, J. M. Q., De Moura, M. F. S. F., Morais, J. J. L., 2009. Application of the end loaded split and single-leg bending tests to the mixed-mode fracture characterization of wood. Holzforschung 63: 597-602 Pohlit, D. J. (2007). Dynamic mixed-mode fracture of bonded composite joints for automotive crashworthiness, Virginia Tech. Rocha, R., Campilho, R., 2018. Evaluation of different modelling conditions in the cohesive zone analysis of single-lap bonded joints. The Journal of Adhesion 94(7): 562-582 Santos, M. A. S., Campilho, R. D. S. G., 2017. Mixed-mode fracture analysis of composite bonded joints considering adhesives of different ductility. International Journal of Fracture 207(1): 55-71 Sekiguchi, Y., Katano, M., Sato, C., 2017. Experimental study of the mode I adhesive fracture energy in DCB specimens bonded with a polyurethane adhesive. The Journal of Adhesion 93(3): 235-255 Szekrényes, A., 2012. J-integral for delaminated beam and plate models. Periodica Polytechnica Mechanical Engineering 56(1): 63-71 Szekrényes, A., Uj, J., 2004. Beam and finite element analysis of quasi-unidirectional composite SLB and ELS specimens. Composites Science and Technology 64(15): 2393-2406 Szekrényes, A., Uj, J., 2007. Over-leg bending test for mixed-mode I/II interlaminar fracture in composite laminates. International Journal of Damage Mechanics 16: 5-33 Wang, J., Ding, H., Jiang, J., Bi, Y., 2023. Experimental and numerical investigation on test methods for mode II fracture of composite ‐ titanium adhesively bonded structures. Fatigue & Fracture of Engineering Materials & Structures 46(10): 3766-3787 Yoon, S. H., Hong, C. S., 1990. Modified end notched flexure specimen for mixed mode interlaminar fracture in laminated composites. International Journal of Fracture 43: 3-9 Zhu, Y. (2009). Characterization of interlaminar fracture toughness of a carbon/epoxy composite material. M.Sc. Thesis