Issue 38

T. Sawada et alii, Frattura ed Integrità Strutturale, 38 (2016) 92-98; DOI: 10.3221/IGF-ESIS.38.12 98 C ONCLUSIONS ultiaxial fatigue evaluation in SGP among the various volume fractions was investigated in this paper. Round- bar specimens molded by injection and compression processes were subjected to static and fatigue tests in room temperature to clarify the effect of molding processes on the multiaxial strength. Tension - torsion combined tests were conducted with various combined stress ratio parameters described as α = τ / σ . General conclusions of this study are as follows. 1. Tsai-Hill failure criteria can be applied to evaluate tension-torsion static strength in SGP with dependence on the molding process and V f . 2. The non-dimensional equivalent stress σ * is defined to evaluate multiaxial fatigue strength by modifying Tsai-Hill failure criteria. 3. The slopes of σ * - N f curve for I-SGP ( n = 26.3) is almost identical to that for C-SGP ( n = 26.2). 4. The relationship between σ * and N f explains the tension-torsion fatigue properties on the double logarithmic chart without depending on a molding process, combined stress ratios α , and fibre volume fraction V f especially for I-SGP. R EFERENCES [1] Sonsino, C.M., Moosbrugger, E., Fatigue design of highly loaded short-glass-fibre reinforced polyamide parts in engine compartments, Int. J. Fatigue, 30 (2008) 1279-1288. [2] Moosbrugger, H., Demonte, M., Multiaxial fatigue behavior of a short-fiber reinforced polyamide–experiments and calculations, Mat.-wiss. U. Werkstofftech, 42 (2011) 950-957. [3] Gaier, C., Unger, B., Dannbauer, H., Multiaxial fatigue analysis of orthotropic materials, Revue de Metallurgie, 107 (2010) 369-375. [4] Quaresimin, M., Susmel, L., Talreja, R., Fatigue behaviour and life assessment of composite laminates under multiaxial loading, Int. J. Fatigue, 32 (2010) 2-16. [5] Launay A., Maitournam M.H., Marco Y., Raoult I., Multiaxial fatigue models for short glass fiber reinforced polyamide – Part I: Nonlinear anisotropic constitutive behavior for cyclic response, Int. J. Fatigue, 47 (2013) 382-389. [6] Launay, A., Maitournam, M.H., Marco, Y., Raoult, I., Multiaxial fatigue models for short glass fibre reinforced polyamide. Part II: Fatigue life estimation, Int. J. Fatigue, 47 (2013) 390-406. [7] Klimkeit, B., Nadot, Y., Castagnet, S., Nadot-Martin, C., Dumas, C., Bergamo, S., Multiaxial fatigue life assessment for reinforced polymersOriginal, Int. J. Fatigue, 33 (2011) 766-780. [8] Tsai, S.W., Strength Characteristics of Composite Materials, NASA CR-224, (1965). [9] Sawada, T., Aoyama, H., Effect of molding process on mechanical properties of glass short fiber/phenolic resin composite, Trans. Soc. Mech. Eng. A Japan, 76 (2009) 672-674. [10] Kawai, M., Yajima, S., Takano, Y., Off-axis Fatigue and Its Damage Mechanics Modeling for Unidirectional Carbon Fiber-Reinforced Composite at Room and High Temperatures, Trans. Soc. Mech. Eng. A Japan, 64 (1998) 2838-2864. [11] Basquin, O. H., The experimental law of endurance tests, Proceedings of ASTM, 10 (1910) 625-630. M