Issue 10

A. Pirondi, Frattura ed Integrità Strutturale, 10 (2009) 21-28; DOI: 10.3221/IGF-ESIS.10.03 27 parameters, possibly dependent on the local stress state. In the specific case of the T-peel test it is important also to know the real fillet dimensions. Figure 8 : Distribution of cohesive strength (AACZ model) obtained as the value of stress in the adhesive normal to the plane of the joint, at the point in the analysis where the uniaxial failure strain was met locally. C ONCLUSIONS he fracture of adhesively bonded T-peel joints was simulated using a Cohesive Zone Model. The CZ parameters were calibrated on fracture tests conducted on a DCB joint bonded with the same adhesive as the T-peels. The explicit modelling of the adhesive layer (AACZ) did not give in this case any significant variation of the parameters with respect to the simpler model where the adhesive was included in the CZ behaviour (ACZ). The T-peel test was simulated first using the set of parameters determined from DCB and the ACZ approach, after a partial recalibration to account for the different thickness of the bondline and for the different metal joined. The results showed a good agreement between experiments and simulations with respect to the propagation phase but the peak load is underestimated and the stiffness is dependent on the modelling of the adhesive at the arm fillet. The simulation with the AACZ approach did not give better results using the same set of parameters. A much better agreement was found using a cohesive strength  m defined as the value of stress in the adhesive normal to the plane of the joint, at the point in the analysis where the uniaxial failure strain was met locally. This means that the crack propagation may be reproduced quite easily tuning the CZ parameters on standard fracture experiments, while the nucleation requires specific parameters, possibly dependent on the local stress state. A CKNOWLEDGEMENTS he author gratefully acknowledge Prof. M. Rossetto, Polytechnic of Turin, Italy, for the experimental data of T- peel joints. R EFERENCES [1] A. J. Kinloch, , Adhesion and Adhesives, Chapman and Hall, London, UK, (1986). [2] J. W. Hutchinson, A. G. Evans, Acta Mater., 48 (2000) 125. [3] I. Mohammed, K.M. Liechti, J. Mech. Phys. Solids, 48 (2000) 735. [4] Q.D. Yang, M.D.Thouless, S.M. Ward, J. Mech. Phys. Solids, 47 (1999) 1337. [5] W. G. Knauss, G. U. Losi, J. Appl. Mech., 60 (1993) 793. [6] H. Hadavinia, A.J. Kinloch, J.G. Williams, in Adv. in Fract. and Damage Mech. II, M. Guagliano and M.H. Aliabadi eds., Hoggar, Geneva, (2001) 445. [7] B. F. Sorensen, Acta Mater., 50 (2002) 1053. [8] B. F. Sorensen, T. K. Jacobsen, Eng. Fract. Mech., 70 (2003) 1841. T T