Issue 43

D. Gentile, Frattura ed Integrità Strutturale, 43 (2018) 155-170; DOI: 10.3221/IGF-ESIS.43.12 170 C ONCLUSION n this preliminary work, delamination mode I and mode II was investigated for different composites made of carbon fiber and epoxy matrix. Test results will be used in order to define a correct experimental procedure for further investigations and as data information for Finite element analysis that will be performed in order to simulate the behavior of a real aircraft component under loading conditions. Bridging (Fig. 18) affected test results. Although bridging improve the material’s delamination resistance, the more common was the bridging, the higher was the experimental scatter. The material design T6 and M1 will be excluded for further consideration because have the lowest critical values of G I and G II . Material M8 will be excluded also because bridging problems have given a high experimental scatter. The materials candidate to further investigations seem to be L2 and T3. L2 shows the highest values of G I and a higher value of G II but shows also bridging problems. T3 has a higher G I and G II values and reduced experimental scatter respect to the others materials investigated as showed in Fig. 19. R EFERENCES [1] Wilkins, D.J., Eisenmann, J.R., Camin, R.A., Margolis, W.S., Benson, R.A., Characterizing delamination growth in graphite–epoxy, damage in composite materials, ASTM Special Technical Publication, 775 (1980) 168–83. [2] Whitney, J.M., Browning, C.E., Hoogsteden, W., A double cantilever beam test for characterizing mode I delamination of composite materials, Journal of Reinforced Plastics and Composites, 1 (1982) 297-313. [3] Ratwani, M.M., Deo, R.B., Resistance curve approach to composite materials characterization, fracture mechanics. ASTM Special Technical Publication, 905(17) (1986) 108–123. [4] Wang, Q.Z., A sandwich three-point bend specimen for testing mode-I interlaminar fracture toughness for fiber- reinforced composite materials, International Journal of Fracture, 85 (1997) 231–240 [5] Miyagawa, H., Sato, C., Ikegami, K., Interlaminar fracture toughness of CFRP in Mode I and Mode II determined by Raman spectroscopy. Composites: Part A, 32 (2001) 477–486. [6] Svensson, D., Alfredsson, K.S., Biel, A., Stigh, U. Measurement of cohesive laws for interlaminar failure of CFRP. Composites Science and Technology, 100(21) (2014) 53–62. DOI: 10.1016/j.compscitech.2014.05.031. [7] Pipes, R.B., Pagano, N.J., Interlaminar stresses in composite laminates under uniform axial extension, J. Comp. Mat., 4 (1970) 538-548. [8] Wang, S.S., Fracture mechanics for delamination problems in composite materials, J. Comp. Mat., 17 (1983) 210-223. [9] AECMA PREN 6034-1995, Aerospace Series Carbon Fibre Reinforced Plastics Test Method Determination of Interlaminar Fracture Toughness Energy Mode II - GIIc Edition P1, (1995). [10] Carlsson, L.A., Gillespie, J.W., Pipes, R.B., On the analysis and design of the End Notched Flexure (ENF) specimen for mode II testing, J. Comp. Mat., 20 (1986) 594-604. [11] Gillespie, J.W., Carlsson, L.A., Pipes, R.B., Finite element analysis of the end notched flexure specimen for measuring mode II fracture toughness, Compos. Sci. and Tech., 26 (1986) 177-197. [12] Russel, A.J., and Street, K.N., 1985, Moisture and temperature effects on mixed mode delamination fracture of unidirectional graphite/epoxy, ASTM STP 876, (1985) 349-370. [13] ASTM standards D 5528 – 01 (Reapproved 2007). I