PSI - Issue 33

M.F.M.O. Rosas et al. / Procedia Structural Integrity 33 (2021) 115–125 Rosas et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 13 overviews the numerical P m for the tubular joints with single modifications and respective combination, as a function of the angle. As visible in the figure, the inner chamfer/adhesive fillet combination presents the best P m results, compared to all single modifications (adhesive fillet, inner chamfer and outer chamfer). However, P m for the combination geometry is virtually identical to using a single adhesive fillet with  =7.5  , which allows to conclude that adding an inner chamfer to the fillet does not increase the mechanical of the joint. Moreover, added to the experimental machining complications, the inner chamfer is actually discouraged, and a single adhesive fillet should be considered instead. On the other hand, the adhesive fillet may be valuable in increasing the joint strength, as formerly discussed.

50

45

40

P m [kN]

35

30

0

30

60

90

 ,  or  [  ]

Outer chamfer Adhesive fillet

Inner chamfer

Geometry combination

Fig. 13. Numerical P m for the tubular joints with single modifications and respective combination.

4. Conclusions CZM validation process was successfully accomplished, by showing P m predictions very close to the experimental average values. The highest offset was 6.1%, for L O =20 mm. The obtained results, including the combination inner chamfer/adhesive fillet, are as follows: • Outer chamfer: major  y /  avg and  xy /  avg stress reductions took place in the adhesive by including this geometric modification with  =7.5º (up to ≈46%). However, due to plasticization of the inner aluminium tube, this improvement did not reflect on P m differences; • Inner chamfer: Additional stress concentrations take place due to the inner chamfer. Minor  y /  avg and major  xy /  avg stress reductions were found (≈15% and ≈60%, respectively), although for different  . Due to tube plasticization P m was left unchanged, but significant elastic stiffness variations of the joint were found, with smaller  yielding more compliant joints; • Adhesive fillet: The fillet causes additional peak stresses at the fillet ends. The overlap end-peak stresses reduce by inclusion of the fillet, up to ≈17% for σ y / τ avg and ≈12% for τ xy / τ avg , although for different  . Due to the increase of shear resistant area at the overlap, a small P m improvement of ≈4% was observed; • Inner fillet/adhesive fillet: A combination with  =30º and  =7.5º was tested. Inner tube plasticization pre vented a significant change in the joint’s behaviour, and the Pm improvement was identical to the use of an adhesive fillet with  =7.5º. It can thus be concluded that the tested geometric modifications highly affect the tubular joints’ behaviour. However, this difference could not translate into major P m improvements due to inner tube plasticization. In futyre works, it would be relevant to test adherend materials with a higher yield point, for improved results. References Adams, R. D. and Davies, R., 1996. Strength of Joints Involving Composites. The Journal of Adhesion 59(1-4), 171-182. Adams, R. D. and Peppiatt, N. A., 1974. Stress analysis of adhesive-bonded lap joints. The Journal of Strain Analysis for Engineering Design 9(3), 185-196. Albiez, M., Vallée, T., Fricke, H. and Ummenhofer, T., 2019. Adhesively bonded steel tubes — Part I: Experimental investigations. International Journal of Adhesion and Adhesives 90, 199-210.