PSI - Issue 28

M.Z. Sadeghi et al. / Procedia Structural Integrity 28 (2020) 1601–1620 M.Z. Sadeghi et al./ Structural Integrity Procedia 00 (2019) 000–000

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Fig. 19: Load-displacement curves for (left) bondline thickness of 0.20 mm, (right) 0.90 mm with different fracture parameters.

From this study, an important conclusion can be arrived upon, apart from the prediction of failure load (P m ). The determined CSERR produces identical results irrespective of the adhesive thickness (t a ) considered. This could be because of stress concentration, existing at the adhesive-adherent interface under mixed-mode loading. Due to the symmetric stress concentration on the upper and lower interface layer imposed by the adherents in the SLJ, energy dissipation is not dependent on the whole adhesive thickness (t a ). In such a context, fracture properties are not dependent on adhesive thickness. Therefore, the G C values determined based on the different mixed-mode ratios can yield to almost identical results and consequently the same circumstances is also valid for the SLJ as a typical mixed mode coupon test. 5. Conclusion Present work investigated the fracture properties of the adhesively bonded joints under mixed mode. Two data reduction methods namely J-integral and ECLM were employed for determination of G C of the adhesive layer (with different thickness) by using DCB and MMB tests (with different mixed-mode ratios). Based on the achieved results, different fracture envelopes by using the B-K fracture criterion were developed. To validate the determined fracture envelopes, the determined values were used to simulate the SLJs with different bondline thickness. It was observed that for SLJs with different adhesive layer thickness, regardless of the type of the fracture envelopes (including the method applied and the adhesive layer thickness) by which values of G C is determined, it can predict identical failure load. References 2009. Abaqus Analysis User's Manual (6.9). Adams, R.D., Peppiatt, N.A., 1974. Stress analysis of adhesive-bonded lap joints. Journal of Strain Analysis 9 (3), 185–196. https://doi.org/10.1243/03093247V093185. Ajdani, A., Ayatollahi, M.R., Akhavan-Safar, A., Martins da Silva, L.F., 2020. Mixed mode fracture characterization of brittle and semi-brittle adhesives using the SCB specimen. International Journal of Adhesion and Adhesives 101, 102629. https://doi.org/10.1016/j.ijadhadh.2020.102629. ASTMD6671. Test Method for Mixed Mode I-Mode II Interlaminar Fracture Toughness of Unidirectional Fiber Reinforced Polymer Matrix Composites. ASTM International, West Conshohocken, PA. https://doi.org/10.1520/D6671_D6671M-13E01. Azevedo, J.C.S., Campilho, R.D.S.G., da Silva, F.J.G., Faneco, T.M.S., Lopes, R.M., 2015. Cohesive law estimation of adhesive joints in mode II condition. Theoretical and Applied Fracture Mechanics 80, 143–154. https://doi.org/10.1016/j.tafmec.2015.09.007. Balzani, C., Wagner, W., Wilckens, D., Degenhardt, R., Büsing, S., Reimerdes, H.-G., 2011. Adhesive joints in composite laminates—A combined numerical/experimental estimate of critical energy release rates. International Journal of Adhesion and Adhesives. https://doi.org/10.1016/j.ijadhadh.2011.09.002. Bascom, W.D., Cottington, R.L., Jones, R.L., Peyser, P., 1975. The fracture of epoxy- and elastomer-modified epoxy polymers in bulk and as adhesives. J. Appl. Polym. Sci. 19 (9), 2545–2562. https://doi.org/10.1002/app.1975.070190917. Benzeggagh, M.L., Kenane, M., 1996. Measurement of mixed-mode delamination fracture toughness of unidirectional glass/epoxy composites with mixed-mode bending apparatus. Composites Science and Technology 56 (4), 439–449. https://doi.org/10.1016/0266-3538(96)00005-X. Blackman, B.R.K., Kinloch, A.J., Rodriguez Sanchez, F.S., Teo, W.S., Williams, J.G., 2009. The fracture behaviour of structural adhesives under high rates of testing. Engineering Fracture Mechanics 76 (18), 2868–2889. https://doi.org/10.1016/j.engfracmech.2009.07.013. Bui, Q.V., 2011. A Modified Benzeggagh-Kenane Fracture Criterion for Mixed-mode Delamination. Journal of Composite Materials 45 (4), 389–