PSI - Issue 13

6

Lukas Loh et al. / Procedia Structural Integrity 13 (2018) 1318–1323 Author name / Structural Integrity Procedia 00 (2018) 000–000

1323

20

20

20

Critical ERR J c Variable Mode-mix ratio I-III Critical ERR G c of MMB- and TDCB-tests

18

18

Critical ERR J c Variable Mode-mix ratio I-III

= 85°

18

16

16

16

14

14

2 )

14

2 )

12

12

= 75°

12

8 ERR (kJ/m 2 ) 10

6 8 ERR J III (kJ/m 10

10

ERR J II (kJ/m

8

6

= 60°

6

4

4

= 45°

4

2

= 15° = 30°

2

2

0

0

0

0.5

1

1.5

2

2.5

3

3.5

4

0

2 )

ERR J I (kJ/m

0

10 20 30 40 50 60 70 80 90 Mode-mix ratio (°)

Fig. 6. Fracture envelope of MC-DCB tests in comparison to results of MMB- and TDCB-tests from literature (viz. Stamoulis et al. (2014)).

Fig. 5. Critical ERR J c vs. mixed-mode ratio.

4. Conclusions

Fracture mechanical tests subjected to mixed-mode I + III loading has been applied on elastic-plastic adhesive joints using the Mixed-Mode-Controlled DCB (MC-DCB) test. For this test, ratio of mode-mixity has been defined on con tributions of J -integral. A test control on those contributions has been successfully realized. Several tests have been considered under constant and variable mode-mix-ratios. Unintended contributions to J integral caused by support / loading conditions has been examined and turned out to be in negligible order of magnitude for nearly the entire experiment. By considering the intended contributions, a fracture envelope has been evaluated on mode-mixity I + III and subsequently compared to results from literature of Mixed-Mode-Bending (MMB) tests. A coherence of both fracture envelopes could not be clearly observed due to di ff erent adhesive layer thicknesses.

Acknowledgments

This work has been supported by Deutsche Forschungsgemeinschaft (DFG) - project-number 329889536. The fi nancial support is gratefully acknowledged. Furthermore, the authors wish to thank Sabine Wenig (Sika AG, Switzer land) for supplying the adhesive and Ihssane Kididane for the very helpful assistance at laboratory work.

References

Standard Test Method for Mixed Mode I-Mode II Interlaminar fracture toughness of unidirectional fiber reinforced polymer matrix composites, 2006. ASTM D6671. Standard Test Method for Fracture Strength in Cleavage of Adhesives in Bonded Metal Joints, 2012. ASTM D3433-99. Determination of the mode I adhesive fracture energy, GIC, of structural adhesives using the double cantilever beam (DCB) and tapered double cantilever beam (TDCB) specimens, 2009. BS 7991:2001. Adhesives - determination of the mode 1 adhesive fracture energy of structural adhesive joints using double cantilever beam and tapered double cantilever beam specimens, 2009. ISO 25217. Loh,L.,Marzi,S.,2018.An Out-of-plane Loaded Double Cantilever Beam (ODCB) test to measure the critical energy release rate in mode III of adhesive joints.Int J Adhes Adhes 83,2430. Rice,J.,1968. A path independent integral and the approximate analysis of strain concentration by notches and cracks. J Appl Mech 35,37986. Loh,L.,Marzi,S.,2018.Mixed-mode I + III tests on hyperelastic adhesive joints at prescribed modemixity. J Adhes Adhes 85,11322. Stamoulis,G.,Carrere,N.,Cognard,J.Y.,Davies,P.,Badulescu,C.,2014.On the experimental mixed-mode failure of adhesively bonded metallic joints. J Adhes Adhes 51,14858. Marzi,S.,Biel,A.,Stigh,U.,2011.On experimental methods to investigate the e ff ect of layer thickness on the fracture behavior of adhesively bonded joints. J Adhes Adhes 31,84050.