Issue34

K. Tanaka et alii, Frattura ed Integrità Strutturale, 34 (2015) 309-317; DOI: 10.3221/IGF-ESIS.34.33 317 Fig. 10(a) shows the change of mode I energy release rate as a function of crack length. The correction factor increases with crack length. It is the largest for TD, and decreases with increasing crack propagation angle  to 30°. For MD and TD, the correction factor F I for an edge crack (  =0) of the stress intensity factor is shown in Fig. 10(b), together with that for isotropic material. It is the largest for TD and smallest for MD, and that for isotropic material is in between. Fig. 11(a) shows the change of mode II energy release rate for three fiber angles where the crack is inclined against the loading axis. The correction factor is the largest for 22.5° plate which has the largest crack angle  =30°. In Fig. 11(b), the ratio of energy release rate of mode II to mode I is plotted against the crack length. It tends to increase with crack length, and is largest for the largest crack angle. The ratio is 20% at most. The calculated data of energy release rate and stress intensity factor were used in the main text to determine the fracture mechanics parameters. R EFERENCES [1] Mandel, J. F., Huang, D. D., McGarry, F. J., Fatigue of glass and carbon fiber reinforced engineering thermoplastics. Polymer Composites, 2 (1981) 137-144. [2] Wyzgoski, M. G. , Novak, G. E., Fatigue fracture of nylon polymers, Part II Effect of glass-fiber reinforcement, Journal of Materials Science, 26 (1991) 6314-6324. [3] Akiniwa, Y., Harada, S., Yagyu, Y., Nakano, M., Effect of fiber content and fiber orientation on fatigue strength of short-fiber reinforced plastics, Journal of Materials Science, Japan, 41 (1992) 1285-1291. [4] Song, J. H., Lim, J.K., Kim, Y.J., Kim, H. G., Low cycle fatigue of PPS polymer injection welds – Fatigue crack behavior-. KSME International Journal, 17 (2003) 647-653. [5] Tanaka, K., Kitano, T., Egami, N., Effect of fiber orientation on fatigue crack propagation in short-fiber reinforced plastics, Engineering Fracture Mechanics, 123 (2014) 44-58. [6] Rybicki, E. F., Kanninen, M.F., A finite element calculation of stress intensity factors by a modified crack closure integral. Engineering Fracture Mechanics, 9 (1977) 931-938. [7] Sih, G.C., Paris, P.C., Irwin, G. R., On crack in rectilinerly anisotropic bodies, International Journal of Fracture Mechanics, 1 (1965) 189-203. [8] Pook, L. P., Frost, N. E., A fatigue crack growth theory, International Journal of Fracture Mechanics, 9 (1973) 53-61. [9] Sih, G.C., Liebowitz, H., Mathematical theory of brittle fracture, in: H. Liebowitz (Ed.), Frature, Mathematical Fundamentals, Academic Press, New York, 2 (1968) 67-190. Figure 11 : Correction factor of mode II energy release rate and ratio of mode II/mode energy release rate. (a) Correction factor of mode II energy release rate. (b) Ratio of mode II to mode I energy release rate.