Issue 53

E. M. Strungar et alii, Frattura ed Integrità Strutturale, 53 (2020) 406-416; DOI: 10.3221/IGF-ESIS.53.31 415 Recommendations on obtaining and mathematical processing of experimental data for determining the mechanical characteristics of composites under shear, using a contactless optical video system have been suggested. To analyze the regularities of mechanical behavior of materials in the areas of process and operational imperfections, the processes of strain and accumulation of damage in sandwich composite objects with pre-embedded defects have been experimentally studied. The authors analyzed the evolution of strain field patterns to assess the development of defects in composite samples. They suggested a technique for studying the effect of defects on the residual strength of composite structural elements based on the joint use of strain fields and temperatures recording systems. Experimental data on assessment of the effect of defects on the residual strength of structurally similar composite structural elements have been obtained. The load-bearing capacity of coarse-grained panels with the damages under cyclic and quasi-cyclic impacts has been assessed. The paper provides a complex study of usability of digital images correlation method for solution of fiber optic technology tasks. It is shown that the use of video-systems for three-dimensional analysis of the displacement and strain fields makes it possible to develop recommendations for location and calibration of built-in fiber optic sensors, and assess the sensitivity to loading modes. A CKNOWLEDGEMENTS xperimental studies were carried out using the large-scale research facilities «Complex of testing and diagnostic equipment for studying properties of structural and functional materials under complex thermomechanical loading» PNRPU modernized with funds by the Ministry of Science and Higher Education of the Russian Federation, Unique project identifier RFMEFI61920X0017. R EFERENCES [1] Staniera, D., Radhakrishnana, A., Genta, I., Shankhachur Roy, S., Hamertona, I., Potlurib, P., Scarpa, F., Shaffer, M., Ivanov, D. S. (2019). Matrix-graded and fibre-steered composites to tackle stress concentrations, Composite Structures, 207, pp. 72–80. DOI: 10.1016/j.compstruct.2018.09.019. [2] Fedulov, B. N., Fedorenko, A. N., Kantor, M. M., Lomakin, E. V. (2018). Failure analysis of laminated composites based on degradation parameters, Meccanica, 53(1-2), pp. 359–372. DOI: 10.1007/s11012-017-0735-9. [3] Hadjem-Hamouche, Z., Derrien, K., Héripré, E., Chevalier, J. P. (2018). In-situ experimental and numerical studies of the damage evolution and fracture in a Fe-TiB2 composite, Materials Science and Engineering: A, 724, pp. 594-605. DOI: doi.org/10.1016/j.msea.2018.03.108 [4] Junshan, H., Kaifu, Z., Hui, C., Ping, L., Peng, Z., Danlong, S. (2017) Stress analysis and damage evolution in individual plies of notched composite laminates subjected to in-plane loads, Chinese Journal of Aeronautics, 30(1), pp. 447–460. DOI: 10.1016/j.msea.2018.03.108. [5] Krzyzak, D., Robak, G., Lagoda, T. (2015). Determining fatigue life of bent and tensioned elements with a notch, with use of fictitious radius, Fatigue & fracture of engineering materials & structures, 38(6), pp. 693-699. DOI: 10.1111/ffe.12276. [6] Lagattu, F., Lafarie-Frenot, M.C., Lam, T.Q., Brillaud, J. (2005). Experimental characterisation of overstress accommodation in notched CFRP composite laminates, Composite Structures, 67(3), pp. 347-357. DOI: 10.1016/j.compstruct.2004.01.016. [7] Tretyakova, T.V., Vildeman, V.E. (2017). Influence the loading conditions and the stress concentrators on the spatial- time inhomogeneity due to the yield delay and the jerky flow: study by using the digital image correlation and the infrared analysis, Frattura ed integrità strutturale, 11(42), pp. 303-314. DOI: 10.3221/IGF-ESIS.42.32. [8] Wildemann, V.E. at all. (2011). The mechanics of materials. Methods and means of experimental research. Perm: Publishers Inc. PNRPU, 165 p. [9] Wildemann, V.E. (2012). Experimental studies of the properties of materials under complex thermomechanical effects. М .: FIZMATLIT, 204 p. [10] Emery, T.R., Dulieu-Barton, J.M. (2010). Thermoelastic Stress Analysis of damage mechanisms in composite materials, Composites Part A: Applied Science and Manufacturing, 41, pp. 1729–1742. DOI: 10.1016/j.compositesa.2009.08.015. E