PSI - Issue 52

Haseung Lee et al. / Procedia Structural Integrity 52 (2024) 252–258 Haseung Lee, Hyunbum Park / Structural Integrity Procedia 00 (2019) 000 – 000

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In the case of stiffness, the intra void was 0.976 in tension and 0.996 in compression, and the case of inter void was confirmed to be 0.983 in tension and 0.997 in compression. 3. Conclusions This study carried out the analysis on the decline of material properties by void fraction by modelling the nonlinear characteristics of lamina. At that time, it considered the hanshin damage condition based on the continuum damage mechanics. This study could draw the following conclusion. Considering Figure 2, the structural analysis results of the virtual coupon test can be observed for each ply break. According to the analysis approach method in this study, the highest decline of mechanical properties was shown when the void size was 300 μ m based on the void fraction of 5%. In addition, it could be found the tensile strength, tensile stiffness, compression strength and compression stiffness decreased by 7.2%, 1%, 7.2% and 0.02%, respectively, as the void fraction increased by 1% based on the intra void diameter of 200 μ m. In case of inter void, tensile strength, tensile stiffness, compression strength and compression stiffness decreased by 18.4%, 0.8%, 18.7% and 0.01%, respectively, as the void fraction increased by 1%. In the case of strength deterioration according to the size of the void, an error that does not show a constant tendency is shown, which is determined to be a limitation of the homogenization method in the program. In the case of inter voids, voids must exist between each ply, so there is a limit to the amount of voids that can be realized, which limits direct comparison with inter voids. However, when comparing the two cases, the impregnation amount of the inter void showed a more pronounced decrease in strength than that of the intra void. Compared to other references, mechanical property degradation tends to occur excessively as the number and size of voids increase, so the nonlinear nature of material damage and more detailed damage conditions need to be considered. Acknowledgements This work was supported by Korea Institute of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea Government(MOTIE) (20213030020120, Development of product quality and O&M technology to improve all-steps reliability of offshore wind turbine blades) References Chen D, Arakawa K and Xu C. 2015. Reduction of void content of vacuum-assisted resin transfer molded composites by infusion pressure control. Polym Compos, 36, 1629 – 1637. Tahir MW, Hallstro¨m S and A ˚ kermo M., 2014. Effect of dual scale porosity on the overall permeability of fibrous structures. Compos Sci Technol, 103, 56 – 62. Uhl K, Lucht B, Jeong H, et al.,1988. Mechanical strength degradation of graphite fiber reinforced thermoset composites due to porosity. In: Thompson DO and Chimenti DE (eds) Review of progress in quantitative nondestructive evaluation. Boston, MA: Springer, 1075 – 1082. Olivier P, Cottu JP and Ferret B.,1995, Effects of cure cycle pressure and voids on some mechanical properties of carbon/epoxy laminates. Composites, 26, 509 – 515. Koushyar H, Alavi-Soltani S, Minaie B, et al., 2012, Effects of variation in autoclave pressure, temperature, and vacuum-application time on porosity and mechanical properties of a carbon fiber/epoxy composite. J Compos Mater, 46, 1985 – 2004 Wisnom MR, Reynolds T and Gwilliam N., 1996. Reduction in interlaminar shear strength by discrete and distributed voids. Compos Sci Technol. 56, 93 – 101. Srinivasulu G, Velmurugan R and Jayasankar S., 2014, Influence of void microstructure on the effective elastic properties of discontinuous fiber reinforced composites. J Compos Mater, 49, 2745 – 2755. Matsuzaki R, Seto D, Todoroki A, et al., 2014. Void formation in geometry-anisotropic woven fabrics in resin transfer molding. Adv Compos Mater 23, 99 – 114. Hsu D and Uhl K.,1987. A morphological study of porosity defects in graphite-epoxy composites. In: Thompson D and Chimenti D (eds) Review of progress in quantitative nondestructive evaluation. Boston, MA: Springer, 1175 – 1184 Xu K and Qian X.,2014. An FEM analysis with consideration of random void defects for predicting the mechanical properties of 3D braided composites. Adv Mater Sci Eng, 12. A. Matzenmiller, J. Lubliner and R. Taylor, 1995, A constitutive model for anisotropic damage in fibercomposites, Mechanics of Materials, vol. 20, no. 2, 125 – 152,