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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case, the material is considered to be isotropic and homogeneous with effective properties corresponding to the experimental data. However, the refinement of the model compared to the one proposed in the standard was to use the FEM when dividing the considered region into solid finite elements. It is further proposed to consider a homogeneous anisotropic medium with known experimental properties and ratios of components taken from reference books for such materials. And, finally, to take into account the uneven distribution of deformations in the massif of the samples working zone, the features of fixing and transfer of loading factors, it was proposed to consider a quasi-layered structure with the same set of anisotropic characteristics in the layer as in the previous step. The conditions of layers interaction are planned to vary. When obtaining simulation results, the effective characteristics are compared with the experimental ones; if necessary, the properties of the medium at the layer level are refined. According to the work plane to determine stress fields, deformations and displacements numerical simulation was carried out. It was performed on mathematical model, which includes the equilibrium equations without mass forces, the Cauchy geometric relations, and the constitutive relations for an isotropic material. This mathematical model was supported by force and kinematic conditions on the surface of the body. Numerical simulation was performed using the ANSYS Mechanical engineering analysis system. Solid-state model samples were created using the Design Modeller software module. Solution was performed for each type of tests. According to the results of calculations, stress, strain and displacement fields were obtained. Also built a graphical dependence of these parameters for different sections of the samples. We will illustrate the results of the composite materials basic characteristics study by the example of determining the shear properties of spatially reinforced composites with allowance for structural features according to the Iosipescu method. Shear deformations were determined using a Vic-3D three-dimensional digital optical system. The evolution of inhomogeneous strain fields on the surface of composite samples of the structure under study is analysed. The variants of averaging the deformations in the working area of the tested samples were analysed using the tools of the Vic- 3D system such as “virtual extensometer (T)”, “rectangular area (R)” and “line (L)” (see for example figure 4,5). With the help of the tool “virtual extensometer (T)”, the parameters of strain gages, optimal for a given structure, are determined, if necessary, to use them. The lengths of the virtual extensometers T 1 and T 2 are selected in accordance with the requirements of the length of the strain gauges from ASTM D5379 and were equal to 1.5 mm (Fig.4). The advantages and features of the tools "rectangular area (R)" and "line (L)" are justified. Assessment of the structural integrity of the composite material under loading was carried out using the AMSY-6 acoustic emission system (figure 6). The relationship between the damage of the composite structure, estimated using the cumulative acoustic emission energy, and the stages of the deformation process is shown, herein the value of the cumulative energy is found by summing the values of the energy parameter in the time interval, and was interpreted as the degree of accumulation of damage in the material.. The conclusion is made about the influence of the structure on the deformation ability of the composite material.

Fig. 4. D eformation diagrams using the “rectangular region (R)” and “virtual extensometer (T)” tools of different lengt hs to determine shear deformations, the layout of the “virtual extensometers (T)” and “rectangular region (R) " on the sample surface.