Issue 38

D. Carrella-Payan et alii, Frattura ed Integrità Strutturale, 38 (2016) 184-190; DOI: 10.3221/IGF-ESIS.38.25 190 V ALIDATION /A PPLICATION he first validation has been conducted on a coupon at constant amplitude loading. The same three points bending analysis as above is run on 80 000 cycles at an imposed load level. A more complex quasi-isotropic layup [0/60/- 60]4s is now studied. The resulting stiffness degradation is compared to experimental data (Fig. 6). The good predictability illustrates the main interest of a ply-level damage law: identification is performed on specific layups, and the resulting material data remains available for any layup without additional identification. Figure 6 : Predictability of stiffness reduction of a 3Pts-bending quasi-isotropic coupon. Further validation cases have been investigated (i.e. flat and V-shaped components) but the overall stiffness degradation contribution from the fatigue loading in these cases were due to the interlaminar delamination. Additional validation cases are under investigations to account for higher stiffness degradations. This brings to the next challenges to extend this methodology to a complete intralaminar and interlaminar fatigue damage solution for variable amplitude and multi-axial loadings. R EFERENCES [1] Sevenois, R.D.B., Van Paepegem, W., Fatigue damage modeling techniques for textile composites: review and comparison with unidirectional composite modeling techniques, Appl. Mech. Reviews, 67 (2015). [2] Van Paepegem W., Development and finite element implementation of a damage model for fatigue of fibre- reinforced polymers, PhD Thesis, Ghent University, Belgium, (2002). [3] Miner, M.A, Cumulative damage in fatigue, Journal of Applied Mechanics, 67 (1945) A159-A164. [4] Matsuishi, M., Endo, T., Fatigue of metals subjected to varying stress, Presented at Japanese Society of Mechanical Engineers, Fukuoka, Japan, (1968). [5] Dowling, N. E., Fatigue failure predictions for complicated stress-strain histories, Journal of Materials, JMLSA, 7(1) (1972) 71-87. [6] Brokate, M., Dressler, K., Krejci, P., Rainflow counting and energy dissipation in elasto-plasticity, Eur. J. Mech. A/Solids, 15 (1996) 705-737. [7] Nagode, M., Hack, M., The damage operator approach, creep fatigue and visco-plastic modeling in thermo- mechanical fatigue, SAE International Journal of Materials & Manufacturing, 4(1) (2011) 632-637. doi:10.4271/2011- 01-0485. [8] Nagode, M., Hack, M., Fajida, M., Low cycle thermo-mechanical fatigue: Damage operator approach, Fatigue Fract Engng Mater Struct, 33(3) (2010) 149-160. [9] Šeruga, D., Hack, M., Nagode, M., Thermomechanical Fatigue Life Predictions of Exhaust System Components, MTZ worldwide, 77(3) (2016) 44-49. [10] Brune, M., et al., FEM based durability analysis of the knuckle of the 5 series BMW, Fatigue Design’98, Helsinki (1998). [11] ASTM D3479, Space Simulation, composite mat., 15.03 (2015). T