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In this paper, the composite patch was prepared by wet spreading method, with which the damaged aluminum alloy specimen was repaired by bonding. The effects of different surface processing and curing modes on the fatigue properties of the specimens were studied. The results show that the surface coating coupling agent can significantly improve the fatigue properties of the repaired specimens; compared with unrepaired specimens, the fatigue life was increased by about 6.26 times and compared with uncoated specimens, the fatigue life was increased by 13.2–32.4%. Compared with unrepaired specimens, the fatigue life of repaired specimens can be increased by 6.20 times by heating and pressure curing. The fatigue life can be increased by 7.8–18.5% compared with normal temperature curing and repairing. Finally, the fatigue fracture of the specimen was observed and analyzed by SEM. [ABSTRACT FROM AUTHOR]

The scope of the investigations of the paper includes the efficiency in the prediction of strength characteristics of the ablating polymer unidirectional carbon-fiber-reinforced plastics at elevated temperatures based on the properties of the unreinforced matrix and a bundle of fibers in the process of thermal oxidative breakdown at different types of stress state. The characteristics of elasticity and parameters of strength of the transverse-isotropic carbon-fiber-reinforced plastic, as well as of its components (epoxy matrix and carbon fibers of T700 type), have been determined in compliance with the regulatory documents of Ukraine at low heating rates with the subsequent exposure of the specimens at the fixed temperature, when the inertia effects can be neglected. It is illustrated that the variation in densities of the ablating unreinforced matrix and the bundle of fibers at elevated temperatures is rather well described via the models of multiphase media employing the modified integral exponential function. The authors analyze the possibility to evaluate the critical stresses of the transverse-isotropic composite at elevated temperatures based on the mechanics of multiphase media considering the thermal and mechanical characteristics of the ablating polymer matrix and the bundle of carbon fibers. It is assumed that the task of heat and mass transfer can be solved separately from the coupled tasks of thermal mechanics of the ablating materials since mechanical stresses have no effect on its parameters. It is found that the calculation of critical stresses using the hypothesis for the total hermetic sealing between the phases or in the assumption on the low pressure in pores determines the lower and upper lines of variation of the composite strength at different types of stress state. In particular, the calculated strength of the unidirectional composite under tension in the transverse direction and in shear along and across the fibers is in good correlation with the experimental data obtained by the authors and other researches. [ABSTRACT FROM AUTHOR]

The paper considers the problem of creating and operating products of reusable space-rocket hardware, in particular with respect to ensuring the integrity of structural elements and safe return to Earth under aerodynamic heating conditions. This problem has two aspects, which differ in specificity of the approaches to designing the elements of space shuttle systems (SSS). The first aspect is associated with ensuring the reliable functioning of the most thermally stressed elements of the re-entry glider, which are structures with large angles of attack, such as fuselage nose and leading edge, wing loading edge, elevators and air intake edges. The second aspect mainly concerns ensuring the allowable temperature level of the spacecraft pressure shell on all flight path segments, especially during re-entry in the Earth's atmosphere. In view of this, one of the main goals in creating SSSs is to develop a reliable heat shield having acceptable size and weight parameters, and cost. The successful solution of these problems is determined in many respects by the optimal choice of appropriate classes of materials: special high-temperature alloys, structural ceramics, highmelting-point metallic and polymeric composite materials. For the modern structures of SSSs, the use of structural metallic materials is worth-while in many respects. Rig test procedures are proposed. A complex of gas-dynamic test rigs was used as the basic equipment, whose fundamental design features and methodological solutions ensure the complete rig test cycle for the solution of problems in both directions. The methodological basis of rig tests is a set of specialized procedures for the simulation of thermally stressed states of the material and the intesity of the external action of the environment, which provide the equivalence of material damage processes and the limit state of the structural element under investigation under model and full-scale conditions. The fundamental basis of these approaches is the classical similarity and dimensional theories, the main postulates of which have been transformed and adapted to the problems of the study of the strength of materials and damageability of structural elements under thermal cyclic loading in corrosive environments. The developed procedures and experimental means allowed the modeling of aerodynamic heating processes of the structural elements of space shuttles. It has been shown that the implemented methods enable the evaluation of functional characteristics, determination of a set of properties and refinement of the technology for the formation of structural elements of aerospace vehicles operating under the conditions of aerodynamic heating to extremely high temperatures. [ABSTRACT FROM AUTHOR]

The paper addresses a problem of optimization of structure of a composite material for smooth panels under strength and stability restrictions. Types of optimal structures have been substantiated. A series of numerical experiments have been carried out to verify the conclusions stated. [ABSTRACT FROM AUTHOR]

The paper provides the strength analysis performed for POLYITAN-2 nano-satellite under quasistatic overload conditions arising at the ascent stage. An efficient solid-state model together with its corresponding finite element model has been developed for nano-satellite. The numerical investigation of the stress-strain state of nano-satellite has been performed using the ANSYS software package. The maximum relative displacements of structural elements, as well as safety factors, have been determined. Different strength criteria were analyzed for the strength assessment of nano-satellite structural elements made of composite materials. It is found the considered POLYITAN-2 structure satisfies the critical strength and stiffness requirements. [ABSTRACT FROM AUTHOR]

The paper demonstrates the urgency of development of composite materials to be used in body armor plates and the potential of application of spodumene glass-ceramic materials as a layer that combines disintegrating and damping properties in the composite structure of a body armor element. The proposed glass-ceramic materials, when subjected to a two-stage low-temperature heat treatment, undergo a bulk fine crystallization with the presence of β-spodumene, thus achieving high mechanical characteristics. [ABSTRACT FROM AUTHOR]

The paper presents the numerical investigation on the stress-strain state of single- and two-layer spheres with spherically transtropic radially reinforced layers under a centrally symmetric internal explosion. A comparative analysis is made between two widely used methods of modeling the explosive loading. The influence of the reinforcing fiber volume fraction and the alternation of layers on the strength of shells is investigated. [ABSTRACT FROM AUTHOR]

The paper describes an application software package developed at the Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine, for the calculation of stress-strain state and strength of multilayer composite cylinders and spheres under internal pulsed loading. The authors show its benefits and limitations in comparison with its modern foreign commercially available counterparts. [ABSTRACT FROM AUTHOR]

We have conducted research on the effect of fiber arrangement on the optimization of the damage to the interface, recently published. We develop in this paper the evolution of the damage in the shearing direction by genetic algorithm. The results obtained by varying the shear rate of the interface of the two materials studied T300 and PEEK, show a good agreement between our genetic approach and the mathematical models presented by Cox and Weibull. [ABSTRACT FROM AUTHOR]

The objective in this paper is to apply the same genetic model as applied in Part 1 to optimizing the shear damage to the fiber-matrix interface of nanocomposite material graphite epoxy. The results show good agreement between the numerical simulation and the actual behavior of the chosen composite and nanocomposite materials, and these results are similar to those obtained by processing techniques of expanded graphite reinforced polymer nanocomposites made by Asma Yasmine. These results were confirmed by calculating the rate of damage with a genetic simulation. [ABSTRACT FROM AUTHOR]

This paper presents the results of investigations on the microcracking of composite ceramic materials, such as electrical engineering porcelain and silicon nitride ceramics, using the acoustic emission technique. The analytical expression describing the kinetics of microcrack accumulation is refined. The influence of the loading rate on the strength characteristics of ceramics and the special features of acoustic emission during their cracking are studied. The dependence of the total acoustic emission count on the stressed surface area of specimens is found. The notion of the microcracking modulus of ceramic composite materials is introduced and its mismatching with the Weibull modulus in strength tests of ceramics is shown. [ABSTRACT FROM AUTHOR]

The objective of this paper is study the influence of the matrix swelling due to water on the damage of the fiber matrix interface of a composite material. The results obtained by a genetic approach based on Weibull probabilistic model, show good agreement between the simulation and the actual behavior of the two materials T300/914 and PEEK/APC2. Also the absorption of water by the matrix increases significantly the interface damage. [ABSTRACT FROM AUTHOR]

The paper addresses the well-known (from available publications) phenomenological strength criteria for anisotropic materials, which are most widely used in application software. [ABSTRACT FROM AUTHOR]

The paper presents a procedure for the determination of torsional deformation relationships for prismatic specimens made of anisotropic material and construction of deformation curves under these conditions [ABSTRACT FROM AUTHOR]

Based on the study of interactions between elements of proposed design and engineering solutions, a unified technique is proposed for analyzing the stress-strain state in joints with a continuous, discontinuous, or a combined bonding layer in components with longitudinally variable geometrical and rigidity parameters, under arbitrary thermomechanical loading. Resolving systems of linear equations are derived, an extent of sufficient discretization of s structure is assessed, and some numerical results are provided. The paper gives recommendations of how to use this technique and demonstrates that it can be efficiently applied to the majority of joint types. [ABSTRACT FROM AUTHOR]

The paper considers a technique for the optimal design of structures made of viscoelastic materials with the purpose of reducing vibration amplitudes at dynamic loads. [ABSTRACT FROM AUTHOR]

The paper presents the results of the investigation into the influence of temperatures from 293 to 3300 K on the strength of carbon-carbon composite materials in tension and in compression. The character of specimen fracture is studied in the temperature range from 293 to 3300 K. It is shown that qualitatively similar changes in the material strength are observed both in tension and in compression. [ABSTRACT FROM AUTHOR]

With the development of various multi-composite materials, there are several methods to study the mechanical properties of materials with complex microstructures. As a typical multi-composite material, foam concrete's mechanical properties and research methods are also widely concerned. To predict the mechanical properties of foam concrete more quickly, we use Python software to realize the random generation of foam pores to establish a random three-dimensional geometric model of foam for many foam concrete materials. Based on the random foam three-dimensional geometric model, the equivalent parameters of foam concrete are calculated by the method of calculating the equivalent parameters of materials in mesomechanics. The relationship of equivalent material parameters between porosity and foam pore diameter is sought. Finally, the tensile calculation of a foam concrete cube with a cohesive unit is carried out to study its stress-strain distribution and the initiation and development of cracks. [ABSTRACT FROM AUTHOR]

The importance and necessity of investigating the influence of a wide range of factors on behavior of composite materials and their real possibilities for operation conditions of rocket-space engineering structure elements are justified. Specifics of material structure and composition, technological processes of their production and design of complex elements, severe conditions of pre-operational tests, direct pre-flight preparation, and effect of complex thermal force factors in the course of controlled flights mean the necessity of experimental studies of the effects of such factors on current and residual physical-mechanical characteristics. For such tasks, the program development results, equipment, and methods of experimental studies of the effect of factors with different character on the integrity of real structures made of polymer composites for different loading modes and types of the stress state are presented. The object of the study is a shell model of a solid fuel rocket engine body made of polymer composite material. Analysis of test results of model shells made of IMS-65 E23 24K+Huntsman unidirectional carbon plastic made by annular winding (90°) under combined loading made it possible to determine the influence of design and technological factors on mechanical properties of these shells and their limit state. New data have been obtained concerning the behavior of such material under the complex action of force loading (compression–tension) and internal pressure (up to 10 MPa), taking anisotropy into account. [ABSTRACT FROM AUTHOR]

Analysis of the effective properties in composite ceramics as mechanical properties analyzer can be a daunting task to handle. Here, we address two of its most prominent hurdles, namely, (i) solving the Eshelby tensor of an arbitrary-shaped inclusion (in this work, we separately consider the interaction tensor outside the inclusion and the Eshelby tensor inside the inclusion), while (ii) effective properties prediction of composite ceramics with arbitrary-shaped inclusion. To overcome the first issue, we derived analytical solution of the Eshelby tensor by Green's function method for the Eshelby problem with an arbitrary-shaped inclusion and analyzed the influence of particle shape (particles with sharp angle and with edge angle) on the Eshelby tensor via numerical method. To approach the second issue, we adopted a recently popular IDD estimate, making changes to calculate the stiffness tensor of composites with inclusions. If the inclusions are randomly distributed in space, the equivalent stiffness of the composite materials is obtained via the direction probability density function and the Voigt method. Experiments on the related finite element analysis show the accuracy of numerical results with regard to the analytical solution of the Eshelby tensor and predict the effective properties of TiC-TiB2 ceramics containing hexagonal prism particles. [ABSTRACT FROM AUTHOR]

The method of determining the parameters of the integral operator of the effective longitudinal elastic modulus of the first-kind composite material is proposed. The viscoelastic transversal and isotropic composite with a periodic structure is used as an object of study. The elements of its cell are the transversal and isotropic viscoelastic matrix and the elastic fiber, which are approximated by hollow and solid cylinders, respectively. The rheological matrix characteristics are described according to the Boltzmann–Volterra hereditary theory. The axisymmetric longitudinal tension of the cell is considered. It is assumed that the radial displacements and stresses on the border between the matrix and the fiber are continuous, the lateral surface of the cell is free from stresses, and axial deformations of the matrix and the fiber coincide. The Laplace transform is applied to solve the obtained boundary value problem. The similar problem in image space is solved for the homogeneous transversely isotropic viscoelastic composite. The effective instantaneous longitudinal elastic modulus and the relaxation kernel are determined via the relation between deformation of the composite and its components, namely the equality of their axial deformations. The proposed method allows one to determine the viscoelastic composite characteristics via the corresponding characteristics of its elements and the volume fractions of the matrix and the fiber in the composite material. [ABSTRACT FROM AUTHOR]

The effect of two-dimensional regular finite-difference mesh spacings on the accuracy of calculation of the dynamic axisymmetric stress-strain state and strength of hollow composite cylinders of finite length, fixed overall dimensions and thickness has been numerically determined by the Wilkins method modified for helical orthotropy and implemented in an application package, created earlier by the authors. The cylinders were made by a ribbon consisting of VMPS glass fibers, impregnated with an ÉDT-10 epoxy binder, on a technological mandrel. Loading is done by exploding a spherical explosive charge in the center of symmetry of a cylinder in an air atmosphere. The obtained results allow one to choose mesh spacings along the radial and axial coordinates, which ensure an acceptable accuracy of determination of the maximum values of hoop stresses and strains, as well as strength functions by maximum stress and strain criteria and by the generalized von Mises criterion. [ABSTRACT FROM AUTHOR]

The dissipative characteristics of rubber-cord composites under the action of cyclic load considering the features of their self-heating have been experimentally investigated. Full-scale uniaxial tension experiments are performed on the plane specimens along the reinforcement fibers of the unidirectional rubber-cord composites. In compliance with the test results, stress-strain curves for the specimens are determined, which form the hysteresis loops under cyclic loading. The tensile testing of the specimens is performed under long-term cyclic loading using the experimental setup INSTRON ElectroPuls E3000 Test System. The process of significant self-heating of the specimens under their long-term cyclic deformation has been experimentally established and studied. Using the non-contact methods, the variation in the specimen temperature in time is measured. The mechanisms of their non-stationary heating are obtained, as well as the dependences of the stabilization temperature of the thermal state on the loading conditions. It has been determined that the area of hysteresis loops, which is formed when specimens undergo deformation in the temperature-stabilized state, depends nonlinearly on the amplitude of strains. The qualitative and quantitative dependences of the loss modulus, as well as the dissipation coefficients and relaxation times on the loading frequency, strain amplitude and temperature due to the material self-heating, are determined. The approximation dependences of the loss modulus of the composite on the loading frequency and self-heating temperature are constructed on the basis of the generalized three-parameter linear (Zener) model and the exponential temperature-dependent initial elastic modulus. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) and styrene-butadiene-styrene (SBS) blends with different mass fractions were prepared in a molten state using a twin-screw extruder. The effect of SBS content on the microstructure and properties of PP/SBS was discussed by studying the morphology and mechanical properties of PP/SBS outdoor aging samples, using differential scanning calorimeter, universal material testing machine, capillary rheometer, X-ray diffraction and X-ray photoelectron spectrometer. The results show that the best performance of unaged composites is 20% PP/SBS composites without added compatibilizer. Low temperature test combined with dynamic thermal analysis found that the addition of SBS effectively improved the low temperature brittleness of PP. XRD tests indicate that SBS can promote the formation of β crystals in PP. Indoor and outdoor aging tests show that samples with 30% of SBS has excellent long-term anti-aging properties. [ABSTRACT FROM AUTHOR]

The evaluation of basic mechanical properties are shown to be of importance for the solid composite propellant development and application. The numerical analysis approach termed the three-phase Voronoi cell finite element method, was proposed to evaluate of the interfacial transition zone effect. Numerical results showed that the performance of the effective modulus could be essentially enhanced by increasing the zone thickness. The module of the composite with the inhomogeneous zone was higher than that of the composite with the homogeneous one. The effect of different zones on volume fractions and matrix moduli was also calculated. The Voronoi method can also be helpful for analyzing the characteristic properties of other three-phase composites. [ABSTRACT FROM AUTHOR]

Shape instability belongs to one of significant types of violation for disposable structural elements under high-stress levels. Due to lack of fundamental data on materials, it is quite problematic to consider the shape instability in the design of disposable structural elements. The crystal plastic finite element method is proposed to investigate the dispersion of shape instability life data. It allows these data to be obtained from traditional material parameters. The shape instability behavior is described with the constitutive crystal model of plastic damage accumulation. Then, to improve the accuracy of life prediction, the new method is developed to construct the simulation model of true microstructure. A modeling algorithm based on the image processing technology is provided to reduce the virtual stresses from the transient crystal plastic modeling method. Comparison of experimental and predicted results shows good agreement at high stresses close to the elastic limit of the material. [ABSTRACT FROM AUTHOR]

The procedure to determine the physical and mechanical characteristics of the anisotropic material with one plane of elastic symmetry has been proposed. Based on the classical theory of elasticity of the anisotropic body the thermoelastic stress state of the multilayered sealing ring of the centrifugal pump rotor wheel made of composite material is studied under thermal exposure with the specified physical and mechanical characteristics. Kinematic and static conditions of the contact between neighboring layers along the conjugated face fronts are considered to be ideal. It is noted that an increase of the temperature on the surface of the composite sealing ring has a considerable influence on the stress state. [ABSTRACT FROM AUTHOR]

The results of experimental investigation on deformation and strength of unidirectional carbonfiber-reinforced plastics made on the basis of carbon fibers T700 and epoxy matrix at room and elevated (up to 260°C) temperatures are presented. The dependences of the elasticity characteristics and strength of the composite on the test temperature are investigated. The metallic characteristics and strength of carbon fibers and matrix at room and elevated temperatures are determined. [ABSTRACT FROM AUTHOR]

A comparison of the numerical results, which are obtained using the application software package developed at the Pisarenko Institute of Problems of Strength under the National Academy of Sciences of Ukraine for the calculation of stress-strain state and strength of multilayer composite cylinders and spheres under internal pulse loading, with the known theoretical and experimental data for a number of composite and metal-composite cylinders under internal axisymmetric explosion. [ABSTRACT FROM AUTHOR]

A method is described to calculate creep and damage in structural elements under cyclic loading. Materials exhibiting anisotropic creep-damage behavior are considered. The results of calculating the deformation and fracture of structural elements at a plane stress state are presented. [ABSTRACT FROM AUTHOR]

For studying the vibration characteristics of a laminar composite rotating blade, the spin softening effect calculated by the finite element method (FEM) was incorporated with the prestress effect to analyze shaking, swing, torsion, and coupled vibrations. The mathematical formula was derived. The study shows that the centrifugal force exerts influence on the difference in vibration frequencies. The laminar composite can reduce an influence of the spin softening on the first swing vibration frequency because of its structure and smaller density. With the variation of rotating velocity, the blade spin softening can lead to the coupled first shaking and first swing vibrations. In the coupled vibrations, swing is contained in the shaking mode and shaking is also contained in the swing one, which is the reason of major blade damages. The results confirm the complexity of the dynamic characteristics of the laminar composite rotating blade. This method is also well applicable to the dynamic design of such blades. [ABSTRACT FROM AUTHOR]

The interfaces in multilayer composite structures are susceptible to delamination due to the combination of active tensile and shear loads under operating conditions. A four-layer center crack composite beam in four-point bending is simulated to determine the interfacial fracture energy of the multilayer structure. The crack is propagating along the interface between the second and third layers. Based on the Euler-Bernoulli theory, the strain energy of the four-layer composite beam is derived. Strain energies before and after the propagation of the interfacial crack are calculated, which results in determining strain energy release rates. Analytical results for those rates are validated with the numerical data obtained by the finite element method. The effect of layer thickness of the composite beam on the interfacial fracture toughness is investigated through a parametric study. [ABSTRACT FROM AUTHOR]

Functionally graded steels (FGS) are a group of functionally graded materials with elastic-plastic properties that are recently produced from austenitic stainless steel and carbon ferritic steel via electroslag remelting process. FGSs provide a possible solution to improve the properties of composites including martensitic and bainitic brittle phases. In the present work, keeping into account the relationship between the impact energy and the notch tip plastic zone size, an analytical model has been developed to predict the Charpy impact energy of bainitic and martensitic FGSs. The Charpy impact energy of the FGSs is compared with that of a specimen made of the homogeneous material corresponding to the layer that includes the notch tip. Moreover, three-dimensional finite element method (FEM) simulation of the process has been carried out via ABAQUS software. The material properties of the layers have been obtained considering the Holloman law for the plastic region. Meanwhile, an exponential variations of the material parameters along the specimen width have been considered. The results of the model show a sound agreement with previous results taken from the literature and the FEM results. [ABSTRACT FROM AUTHOR]

The most common methods for determination of mechanical characteristics of composite materials are considered. The accuracy of methods for each constant of some unidirectional composite materials based on E-glass fibers and epoxy binder is found. [ABSTRACT FROM AUTHOR]

This composite has been developed by addition of 0.5 to 3.5 wt.% powders of TiO to aluminum melt by semisolid-metal processing of aluminum alloy. Dry sliding wear behavior of pins of cast composite, fabricated by solidification of melt-particle slurry in mold, has been determined by pin-on-disk wear tests carried out conventionally and while removing wear debris by camel brush. The accumulated volume loss in composites increases linearly with increasing sliding distance and the wear rate increases more or less linearly with increasing load. Increasing particle content decreases wear rate at a given load. The accumulated volume loss is considerably higher when wear debris is removed by camel brush during dry sliding wear. The relatively brighter compacted oxide transfer layer could be observed in the SEM micrograph of worn pin surfaces of the composites developed by addition of TiO. At higher loads, the oxide debris are expected to get better compacted to form transfer layer, spread over a larger area of the sliding surface and thus, their removal causes a larger wear compared to that without removal of wear debris. [ABSTRACT FROM AUTHOR]

The results of investigations of the mechanical characteristics of tungsten, alloys and composite materials based on it, which are used in space-rocket hardware, have been generalized. The investigations were carried out under short-time, sustained static and low-cycle loading conditions on small time bases in a temperature range of 290-3020 K. [ABSTRACT FROM AUTHOR]

The adhesive strength of epoxy composite coatings modified by magnetic field and ultraviolet irradiation, and filled with dispersed particles of different physical nature has been studied. The content and conditions of formation of protective epoxy composite coatings have been optimized using the method of mathematical experiment planning. [ABSTRACT FROM AUTHOR]

The fatigue strength of STÉF-1 composite with glass fibers and epoxy-phenolic binder is investigated experimentally, and the damage accumulated therein is estimated. The investigations were performed on a special test bench DP-5/3 designed for determining the fatigue strength in bending of sheet specimens under symmetrical cycle of loading. The specimens were cut along the warp and weft directions of the fiber glass fabric and were brought to destruction under severe conditions of loading. The experimental results on the fatigue fracture of specimens were processed by the least square method. The parameters of the energy-based model for fatigue damage of the composite material are determined. A reasonably good agreement between the theoretical and experimental data is obtained. [ABSTRACT FROM AUTHOR]

We investigate the structure, hardness, strength, plasticity and fracture character of Cu–Cr microlayer composite material for electric contacts with prescribed microlayered structure and chemical composition in the temperature range from 290 to 1070 K. The correlation relationships between the hardness and strength characteristics have been established. [ABSTRACT FROM AUTHOR]

The analysis of stiffness degradation and the identification of damage mechanisms during and after fatigue tests of sandwich panels with PVC foam cores have been performed. The sandwich panels with cross-ply laminates skins made of glass fiber and epoxy resin were manufactured by vacuum moulding and subjected to three-point bending tests. Two PVC cores of similar type but with differing densities were investigated. The effect of core density and thickness on the damage behavior was highlighted. Using the cyclic life criterion, fatigue curves were plotted according to two models and compared with those of the literature. It has been demonstrated that the sandwich SD 2, with the higher core density, withstands a higher load and possesses greater rigidity in static tests, combined with an enhanced fatigue resistance, when compared to sandwich SD 1 which has a lower core density. [ABSTRACT FROM AUTHOR]

A detailed knowledge of dependence of mechanical properties on orientation in materials prepared by directional processes may present an important factor influencing the design of construction parts. Toward this end, the compressive creep testing of short specimens may be useful. Three different magnesium-based materials were subjected to this testing: (i) pure magnesium, (ii) magnesium matrix composite reinforced with 10 vol.% of titanium, and (iii) magnesium alloy WE54. All three materials were prepared through a powder metallurgical route with final hot extrusion. The specimens for creep tests were cut in such a way that their longitudinal axis (i.e., the direction of compressive creep stress) and the axis of extruded bar contained a predestined angle. Two extreme cases can be observed: In pure Mg and in Mg-Ti composites, the dependence of the creep rate is very sensitive to the orientation especially at small inclinations from extrusion axis. The greatest creep resistance is observed in specimens with stress axis parallel to the extrusion axis, the lowest at declinations from 45 to 90°. On the other hand, in WE54 no orientation dependence was observed. Possible explanations of the behavior based on microstructural observations are discussed. [ABSTRACT FROM AUTHOR]

The elastic-deformation behavior of unidirectional carbon-fiber-reinforced epoxy laminates is investigated. The effect of operating temperature decrease to 77 K on their deformation and strength is studied. The effectiveness of prediction of stiffness and compliance parameters and load-carrying ability of laminated carbon-fiber-reinforced composites has been analyzed on the basis of mechanical characteristics of the fiber and matrix. [ABSTRACT FROM AUTHOR]

The authors address the problem of cyclic strength analysis of aluminum alloys under static and cyclic loading. The calculations are performed by means of limiting state models representing all of the known forms of limit stress diagrams. [ABSTRACT FROM AUTHOR]

The author presents and discusses the results of investigation to verify the design principles for jointing composite components. Based on the findings, novel design and engineering solutions for metal-composite joints are put forward. To ensure an effective transition from a composite material to a metal butt-joint fitting, new jointing techniques have been developed involving the use of embedded longitudinal and transverse fastening microelements in a composite material, which are molded into or mounted on a metal component. A modification of half-stitch jointing is proposed which enables the joint to work in compression and reduces the pressing stresses in the winding zone. Based on the study of force transfer conditions in the proposed joint design and the jointing solutions, the author defines the main lines of theoretical and experimental investigations to support the engineering and stress analysis activities. The experimental static strength assessment demonstrates effectiveness of the proposed solutions. [ABSTRACT FROM AUTHOR]

We have studied the effect of residual stresses on fracture resistance and crack arrest behavior of asymmetric ceramic laminated Si3N4/Si3N4-TiN structures. Using the compliance method, we assessed the technique of R-curve construction for laminar composites. For laminar structures with layers varying by their elastic characteristics we developed an analytical method for calculation of "fracture resistance - crack length" dependence. The method applicability is verified by calculation of stress intensity factors for laminar specimens with an edge crack The calculated results are compared to the experimental data. [ABSTRACT FROM AUTHOR]

Within an experimental approach we describe the mechanical behavior of different resin-epoxy laminates reinforced with cross-ply Kevlar and glass fibers under conditions of static and cyclic three-point bending. In static tests, we consider the effect of stacking sequence, the thickness of 90°-oriented layers, reinforcement type on the mechanical behavior of laminates under loading and on realization of various damage modes leading to rupture. Cyclic loading studies have been performed in two steps. In the first stage, we inquire into the dependence of the behavior and durability of four glass fiber-reinforced laminate-types on the stacking sequence; the second stage is devoted to studying the dependence of cyclic strength and fatigue behavior of laminates on the reinforcement type. Fatigue tests are carried out in load-control regime for glass and hybrid (Kevlar + glass) fiber laminates. Fatigue curves are constructed in coordinates “stress – number of cycles until fracture” from the criteria corresponding to a drop in stiffness by 5 and 10%. Analysis of the results obtained permits evaluation of the effect of the stacking sequence and the reinforcement type on the behavior of cross-ply laminates in cyclic loading. The presence of Kevlar fibers accounts for nonlinear behavior of laminates in static tests and for low cyclic strength in fatigue tests under three-point bending. [ABSTRACT FROM AUTHOR]