PSI - Issue 25

R.M.D. Machado et al. / Procedia Structural Integrity 25 (2020) 71–78 Machado et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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L O =12.5 mm) and a minimum deviation of 33% (  =0.5 and L O =50 mm). As for the linear softening propagation criterion, the predictions were similar for all values of α , and irrespectively of L O . The maximum deviation for the linear power law was 14% (  =2 and L O =37.5 mm). Moreover,  =1 criterion is the most suitable to capture this adhesive behavior by presenting the lowest deviations between all criteria, i.e. 7, 3, 4 and 0% for L O =12.5, 25, 37.5 and 50 mm, respectively.

5. Conclusions

This work aimed at validating the XFEM to predict the tensile behavior of stepped-lap joints, as a function of the geometry ( L O ). Initially, an experimental analysis was carried out. showing that P m of the stepped-lap joints highly varies with the L O . The XFEM analysis began with the study of the damage initiation criterion. The MAXS and QUADS damage initiation criteria (stress based) generally worked well, with percentile deviations to the experiments generally below 10%. The other criteria gave results much offset from the real behavior. The study of the damage law shape and mixed mode exponent followed, showing that the triangular damage law generally works much better than the exponential law. Between the different  exponents,  =1 was generally the best solution for the strength prediction of bonded joints. Thus, it was demonstrated that, if the modelling conditions are carefully chosen, the XFEM is a powerful tool for the strength prediction of adhesive joints. Abaqus® (2013). Documentation of the software Abaqus®. Dassault Systèmes. Vélizy-Villacoublay Barenblatt, G. I., 1959. The formation of equilibrium cracks during brittle fracture. General ideas and hypothesis. Axisymmetrical cracks. Journal of Applied Mathematics and Mechanics 23, 622-636. Belytschko, T. and Black, T., 1999. Elastic crack growth in finite elements with minimal remeshing. International Journal for Numerical Methods in Engineering 45(5), 601-620. Bendemra, H., Compston, P. and Crothers, P. J., 2015. Optimisation study of tapered scarf and stepped-lap joints in composite repair patches. Composite Structures 130, 1-8. Campilho, R. D. S. G., Banea, M. D., Neto, J. A. B. P. and da Silva, L. F. M., 2013. Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer. International Journal of Adhesion and Adhesives 44, 48-56. Campilho, R. D. S. G., Banea, M. D., Pinto, A. M. G., da Silva, L. F. M. and de Jesus, A. M. P., 2011. Strength prediction of single- and double lap joints by standard and extended finite element modelling. International Journal of Adhesion and Adhesives 31(5), 363-372. Carvalho, U. T. F. and Campilho, R. D. S. G., 2016. Application of the direct method for cohesive law estimation applied to the strength prediction of double-lap joints. Theoretical and Applied Fracture Mechanics 85, Part A, 140-148. Carvalho, U. T. F. and Campilho, R. D. S. G., 2017. Validation of pure tensile and shear cohesive laws obtained by the direct method with single lap joints. International Journal of Adhesion and Adhesives 77(Supplement C), 41-50. Davis, M. and Bond, D., 1999. Principles and practices of adhesive bonded structural joints and repairs. International Journal of Adhesion and Adhesives 19(2 – 3), 91-105. de Sousa, C. C. R. G., Campilho, R. D. S. G., Marques, E. A. S., Costa, M. and da Silva, L. F. M., 2017. Overview of different strength prediction techniques for single-lap bonded joints. Journal of Materials: Design and Application - Part L 231, 210-223. Moës, N., Dolbow, J. and Belytschko, T., 1999. A finite element method for crack growth without remeshing. International Journal for Numerical Methods in Engineering 46(1), 131-150. Pike, M. G. and Oskay, C., 2015. XFEM modeling of short microfiber reinforced composites with cohesive interfaces. Finite Elements in Analysis and Design 106, 16-31. References