PSI - Issue 17

Andrey V. Babushkin et al. / Procedia Structural Integrity 17 (2019) 658–665 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Ilyushin and Pobedrya (1970) hypothesis about the transfer of properties. The problem lies in rethinking the Ilyushin hypothesis about the transfer of properties at the present stage of experimental and computing equipment development, methods and tools of analysis. This problem is particularly relevant for rapidly developing composite materials and structures. In this case, the complex stress-strain state in the working zone of the samples can be fully estimated by calculation, through modeling the adaptive structure of the sample structures and the construction of non-uniform deformation and stress fields. Moreover, the installation information for such a simulation can be obtained in the course of conducting basic tests of standard samples, determining the generally accepted characteristics corresponding to the Ilyushin hypothesis. The aim of this work is developing fundamental experimental knowledge about the behavior of polymer composite materials samples (structural elements) during the implementation of non-trivial test methods; modeling and construction of inhomogeneous strain-stress state in the samples working area and evaluation of the mechanical characteristics ratio, defined from ASTM standards of the comparison of composite materials-structures with the calculated non-uniform deformation fields and stress parameters. The overall goal defines the objectives of the study. First, testing of the polymer composite materials with various structures of fibrous reinforcing systems (layered composites, layered with additional amplification using the transverse direction weaving method (Tufting), obtained by 3D weaving methods, etc.) samples (structural elements) complex to obtain integral mechanical characteristics comparison of materials according to the recommendations of experimental techniques. In this case, for example, use a number of non-trivial ASTM techniques (bending of a bent beam, stretching-compressing samples with an open holl, material collapse in a hole with a rigid axis, compression of plates after impact, etc.) for testing composites. Secondly, to model of non-uniform strain-stress state in the working areas of the same samples. In this case, use one of the calculation packages (ANSYS). As a theoretical basis, use the structural-phenomenological model of composite materials deformation and fracture. As installation and validation data - the results of own experiments and well-known reference information. In addition, do a comparative analysis of the experimental research results and modeling in order to verify the integral characteristics and assess their compliance with certain parameters of non-uniform deformation and stress fields. To achieve this goal, the team of authors had a significant scientific background: Lobanov and Babushkin (2012), Wildemann (1997), Tashkinov and Strungar (2017), Wildemann (2011, 2012). Previously obtained theoretical results, scientific approaches and methods include such provisions as the structural-statistical model of fibrous composite deformation and fracture; probabilistic model of strength, crack resistance and cyclic durability of a unidirectional fiber composite, long-term thermal strength of glass-reinforced plastics during operation on pulp and reagent lines; prediction of powder materials physical and mechanical properties; the results of experimental studies and methods of metals, alloys, plastics and structurally inhomogeneous materials (composites) static and fatigue properties, as well as the mechanical characteristics of these materials under conditions of complex stress state and complex thermomechanical effects by Babushkin and Lobanov (2012), Babushkin et.al (2014), Wildemann et.al. (2012). As part of this study an analysis of standard and approved testing methods for samples of composite materials was carried out. The basis is the ASTM standards system. To detect the material characteristics the "basic" tests and standard methods for defining the comparison characteristics were determined. Comparison characteristics are generally relative and are measured in the same units as the basic material characteristics. Moreover, the development and diversity of composite technologies and structural design solutions often force designers and researchers to use "basic" tests with violations of certain standards restrictions. This happens for well-known reasons for the complexity of samples selection and the limitations of the mathematical apparatus of standard techniques. As a result, arises a situation where for entire groups of new and advanced composite materials (asymmetrical with respect to the styling plane, complexly filled, having longitudinal and transverse radii, stitched fabrics and obtained from 3D preforms, etc.), the concept of “basic” test methods with the definition the basic characteristics of these materials disappear, and the data obtained in the course of such tests differ little from the characteristics of the comparison and differ greatly from the characteristics corresponding to Ilyushin's hypothesis of properties transfer. In this case, it is also impossible 2. Task setting. Scientific and technical background