The well-known equations of photoelasticity of linear viscoelastic bodies are used to describe the photoelastic behavior of a viscoelastic orthotropic plate with a crack. Expressions for the stress intensity factors (SIFs) at the crack tip are obtained using photoelastic measurements. The time dependence of the SIFs is analyzed and shown to be determined by the angles between directions of the crack and tension Keywords: photoelasticity, viscoelastic orthotropic plate with a crack, tension, stress intensity, fracture Introduction. Intensive loading causes early damage of the material of structural members due to the growth of existing and the initiation of new submicro-and microdefects. In many fibrous composites, such processes mainly occur at the fiber-matrix interface. Even at normal temperature, they show viscoelastic behavior [15]. Experimental data [3,4,10,12] suggest that the fracture of such materials largely depends on their rheological properties and may occur at low stresses as a slowly growing crack. Efficient experimental nondestructive methods for the quantitative assessment of the damage of anisotropic materials under loading, especially in the plastic range, are yet to be developed.Among the direct nondestructive methods that could be used to study the kinetics of damage growth, the acoustic-emission method is the most promising [1]. A review of literature on the use of this method for the evaluation of accumulated damage shows that some well-known data are empirical, which significantly limits their use [14].The photoelastic method makes it possible to determine stresses and strains and also their distribution in anisotropic optically sensitive materials with accuracy sufficient for engineering [9,13].Solutions to nonstationary problems of fracture mechanics for anisotropic bodies with stress concentrators obtained by the dynamic photoelastic method can be found in [17-22, etc.].We will outline a technique for the determination of the stress intensity factors (SIFs) near cracks in linear viscoelastic materials based on photoelastic measurements. We will discuss results on the variation in the SIFs during precritical crack growth.1. Problem Formulation and Method of Analysis. Consider a plate made of a linear viscoelastic fibrous composite and having a central crack. The crack is parallel to the direction of preferential reinforcement of the orthotropic composite (Å Å

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The stress-strain state near cracks on the boundary of a circular hole in a linear elastic orthotropic composite plate under tension is analyzed. The distribution of stress intensity factors (SIFs) at the crack tip is found from photoelectric measurements. The dependence of the SIFs on the ratio of crack length to hole radius and on the mechanical properties of the material is established Keywords: photoelasticity, orthotropic composite plate, circular hole with two edge cracks, tension, stress intensity factor Introduction.Theoretical and experimental studies of the stress distribution in composite structural members (plates and shells with stress concentrators (holes, cracks)) are addressed in [1, 3, 6, 7, 11-16, etc.)].To determine the stress intensity factors (SIFs) around cracks propagating from the edges of a hole in elastic isotropic plates, use is made of numerical [1, 3], theoretical-and-experimental [2], and experimental [8] methods. The major results in the field have been obtained in the static case. Solutions to dynamic problems for anisotropic bodies with stress concentrators obtained by the photoelastic method can be found in [12][13][14][15].We will use photoelastic measurements to study the stress distribution around cracks on the boundary of a hole in linear elastic fiber-reinforced composite plates under a tensile force normal to the cracks. Use will be made of a procedure that produces more accurate results than in [16]. The mathematical model discussed below allows us to increase the neighborhood around the crack tip to improve the accuracy of determining the fringe orders and, hence, the SIFs.1. Problem Formulation. Procedure of Analysis. To describe the mechanical and optical behavior of the composite, we will assume that it is homogeneous and anisotropic. Consider a photoelastic plate under creep.The orthotropic plate is weakened by a crack on an interval ( ) 2l of the x-axis aligned with the principal axis of orthotropy of the material (Fig. 1). The plate is subject to a tensile force P = const applied far from the stress concentrator. In the case of plane stress state, the components of the stress tensor s s t

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Рекомендовано до друку вченою радою Національного університету «Острозька академія» (протокол № 4 від 31 жовтня 2019 року) Рецензенти: М. Р. Литвин-доктор історичних наук, професор Г. М. Стародубець-доктор історичних наук, професор Відповідальний за випуск-к.і.н., доц. М. Близняк Нариси воєнно-політичної історії України: навчальний посібник / Атаманенко В., Близняк М., Войтович Л. та ін. Вид. 2-ге, переробл. і доповн. Острог, 2020. 568 с.