PSI - Issue 50

Alexander Eremin et al. / Procedia Structural Integrity 50 (2023) 65–72 Alexander Eremin / Structural Integrity Procedia 00 (2019) 000 – 000

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matrix in the transverse direction. Moreover, aramid fibers are interlocked in bundles because it is a fabric. Bundles are constrained and cannot participate in the structural rearrangement. The combined action of these effects leads to higher deformations of the matrix, but slightly less deformations of the fiber itself. The strain fields for an orthotropic CFRP are smoother, and the distribution of deformations occurs uniformly up to the final failure. The orthotropic composite, which has fibers on the outer layer directed along the specimen, does not show any significant localization and fails along the entire length of the sample. In a quasi-isotropic CFRP the outer layer contains fibers at an angle of 45°. The deformation of the fibers is visible in the strain fields, but, nevertheless, the overall distribution is uniform without localization. 5. Conclusions The layup of the composite determines its mechanical properties, as well as the nature of the mechanical behavior. In the case of an orthotropic or unidirectional composite, deformation processes are well understood. When using quasi-isotropic laminates, the presence of layers where fabrics or fibers are aligned at an angle of ±45° to the loading axis complicates the mechanical behavior. A rotational deformation mode appears, as well as an in plane shear. At the same time, the compliance and nonlinearity of fiber deformation also affect the deformation processes occurring in the material. The pliability of aramid fibers, their high potential for deformation, as well as the woven of fibers into a fabric, leads to localization of deformations in the area of bundles due to the combined action of these factors. Considering the reinforcing layers only at an angle of ±45° (ASTM 3518 standard), one can see that the localization of deformations in composites based on aramid and carbon fibers occurs in different ways. At low strain level, pliable aramid fibers distribute the load well over the entire sample area. Stiff carbon fibers cannot achieve such a distribution and deformations are localized along the shear planes. First of all, this is caused by uneven laying, when there is no preload of the fibers and stresses are transferred unevenly. At a high level of deformation, the reverse situation has been observed. Due to the high compliance, the aramid composite easily reaches the nonlinear stage, relaxing the external load due to significant local inelastic deformation. Carbon fibers at high loads are rearranged and involved in the bearing capacity of the composite more evenly, while maintaining the linear behavior. Acknowledgements This work has been supported by the Russian Science Foundation, grant 21-79-10385. References Sutton, M.A., Orteu, J.-J., Schreier, H., 2009. Image Correlation for Shape, Motion and Deformation Measurements, Springer US, Boston, MA, pp. 322. Lecomte-Grosbras, P., Paluch, B., Brieu, M. , De Saxcé , G., Sabatier, L., 2009. Interlaminar shear strain measurement on angle-ply laminate free edge using digital image correlation. Composites Part A: Applied Science and Manufacturing 40, 1911 – 1920. Laurin, F., Charrier, J.-S. , Lévêque , D., Maire, J.-F., Mavel, A. , Nuñez , P., 2012. Determination of the Properties of Composite Materials Thanks to Digital Image Correlation Measurements. Procedia IUTAM 4, 106 – 115. Vrgoč , A. , Tomičević , Z., Smaniotto, B., Hild, F., 2021. Application of different imaging techniques for the characterization of damage in fiber reinforced polymer. Composites Part A: Applied Science and Manufacturing 150, paper #106576. Jim, J.-M., Chen, J.-L., Guo, G.-P., Chen, X.-W., Wang, X., 2013. Measurement of elastic constants for aviation composite materials using digital image correlation method. Cailiao Gongcheng/Journal of Materials Engineering, 80 – 85. Ullah, H., Harland, A.R., Blenkinsopp, R., Lucas, T., Price, D., Silberschmidt, V. V., 2011. Analysis of Nonlinear Shear Deformations in CFRP and GFRP Textile Laminates. Applied Mechanics and Materials 70, 363 – 368. Liang, Y., Wang, H., Gu, X., 2013. In-plane shear response of unidirectional fiber reinforced and fabric reinforced carbon/epoxy composites. Polymer Testing 32, 594 – 601. Martin-Barrera, C., Soberanis-Monforte, G.A., Gonzalez-Chi, P.I., 2018. Dimensional Scaling and Failure Pattern of the Tensile Properties of Angle-Ply Thermoplastic Composites of Twaron Fiber/Polypropylene. Frontiers in Materials 5.