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V. Dattoma et al. / Procedia Structural Integrity 18 (2019) 719–730 Author name / Structural Integrity Procedi 00 (2019) 000–000

(a)

(b) Fig. 16. (a) Contact pressure head rivet-laminate model A and (b) B.

4. Conclusions In this work the whole junction stiffness under load was evaluated and preliminary analysis show both the coefficient of friction and preload induce less significant alteration of the composite joint behaviour. The problem complexity arises with the significance of the friction and pre-tension load of the fastening system, affected by simultaneous contact non-linearity in extremely localised regions around the hole. A deeper investigation with both models (A and B) revel that refined model (model B) has higher rigidity than simplified model (model A), but real experimental data of stress/strain curve are placed in between. On refined models B, a 3D Hashin-type failure criterion was used to introduce progressive damage of the matrix and fibres. From the results, it is observed the beginning of the macroscopic damage to occur around already at small load levels (8.726 kN), with a percentage error up to 20%, with respect to the experimental data. Various failure modes were analysed. Damage begins around the hole where contact conditions with the bolt head are more severe and is evenly distributed in various plies, leading to final rupture of second or third one. Finally, delaminations were introduced in the model B since the cohesive model may produce results more reliable, mainly because the initial compression collapse in critical layers in contact with rivet will affect the inner layers, giving rise to successive internal delaminations propagating in width. References Tong L., 2000 Bearing failure of composite bolted joints with non-uniform bolt-to-washer clearance. Composites Part A: Applied Science and Manufacturing,. 31(6): p. 609-615. Camano, P.P. and Matthews, F.L., 1997, Stress analysis and strength prediction of mechanically fastened joints in FRP a review. Composite part A. Dattoma , V., Nobile , R., Scarselli, G., Panella, F.W., 2013, Fatigue testing of CFRP aeronautical laminates for bearing behaviour characterisation, in: 9 th International Conference on Composite Science and Technology, Sorrento, Italy, 24–26 April. G. Scarselli, E. Castorini, F.W. Panella, R. Nobile, A. Maffezzoli, “Structural behaviour modelling of bolted joints in composite laminates subjected to cyclic loading,” Aerospace Science and Technology, Vol. 43, pp. 89-95, 2015. Chang, F.K. and Chang, K. Y. (1987). A progressive damage model for laminated composites containing stress concentration. Composite Mater 21, 834-855. Yamada, S. E. and Sun, C.T. (1987). Analysis of laminate strength and its distribution. J. Composite Mater.12, 275-84. Hashin, Z. (1980) Failure criteria for Unidirectional fibre composites J Appl. Mach 47, 329-34. Van den Bosch, M., Schreurs, P., Geers, M., 2006, An improved description of the exponential Xu and Needleman cohesive zone law for mixed mode decohesion. Eng Fract Mech 73, 1220–1234. Xu, X.-P. and A. Needleman, 1993, "ContinuumModelling of Interracial Decohesion," in Dislocations 93, Solid State Phenomena Vol. 35-36, 287 302, September. R.A. Ibrahim, C.L. Pettit, 2005Uncertainties and dynamic problems of bolted joints and other fasteners, J. Sound Vib., 279, () pp. 857-936. T.N. Chakherlou, H. Taghizadeh, A.B. Aghdam, 2013, Experimental and numerical comparison of cold expansion and interference fit methods in improving fatigue life of holed plate in double shear lap joints, Aerosp. Sci. Technol., 29, pp. 351-362. A.S. Kaddour, M.J. Hinton, 2013, Maturity of 3D failure criteria for fibre reinforced composites: comparison between theories and experiments, Part B of WWFE-II, J. Compos. Mater., 47(), pp. 925-966.