The effects of TiO2 microparticle blending on the mechanical and thermal properties and the water absorption behavior of hybrid Pinus/Shorea robusta wood particulate-epoxy composites have been investigated. The tensile, flexural, impact, microhardness, and water absorption tests and a thermogravimetric analysis were performed for the hybrid composites. The results obtained, in comparison with those

The paper presents results of changes in the extreme values (minimum and maximum possible) of the tensile strength of threads and single filaments of an aramid fiber as a result of its processing by a suspension of carbon nanotubes in the production process. It is shown that the shift in the parameter of the Weibull–Gnedenko distribution for threads, which characterizes the point of fracture onset

A fractal model allowing one to theoretically estimate the shearing strength of the interfacial contact in a polymer-carbon nanotube system is proposed. It takes into account the structure of carbon nanotube surface and describes experimental data accurately enough. This makes the model promising for predicting the polymer/nanofiller contact strength. As a function of nanotube diameter and contact

For the first time, the effect of γ-radiation (with doses of 5, 10, 15, and 20 Mrad) on the structure and mechanical characteristics of a polymer composite material based on low-molecular-weight rubbers has been studied. It is shown that an increased radiation dose increases its breaking stress and decreases the breaking strain. The fracture energies are calculated from experimental values of the breaking

A modified Mori–Tanaka model to predict the average mechanical characteristics for dispersedly reinforced materials considering the physical nonlinearity, especially plasticity, of its constituents is proposed. A comparison of theoretical results with experimental data showed that this modification provides a sufficiently high accuracy of calculated estimates for parameters of the stress-strain state

Results of a work on evaluation of the effectiveness of promising vibration diagnostic technologies on the basis of an operating helicopter with an experimental system for monitoring the state of structures are presented. To move towards a practical application of the monitoring system based on the Operational Modal Analysis (OMA), it is necessary to assess its ability to distinguish actual defects

Aiming at the phenomenon of delamination and serious tool wear when processing carbon-carbon composite materials by traditional mechanical tools, an abrasive water jet reaming process for carbon-carbon composites is proposed. First, the carbon-carbon composite material is prepunched by a certain method, and then the abrasive water jet is used for cutting and reaming. The internal stresses and interlayer

Experimental tests and numerical studies were performed to investigate the burst performance of thermoplastic composite pipes (TCPs) under internal pressure. A progressive damage model is established to predict the burst behavior of TCPs, in which different failure criteria and the damage evolution of a composite material are considered and directly incorporated into the ABAQUS with a user-defined

Fibre-reinforced polymer (FRP) composite materials are widely used in different branches of industry, especially in aerospace, owing to their low mass, high strength and stiffness, and good fatigue and corrosion resistance. However, these materials are prone to the impact damage. Especially dangerous are barely visible impact faults, since it is difficult to detect them. If left unrepaired, they can

The power spectral density (PSD) of an equivalent stress is proposed to analyze the fatigue life of composite laminates under random vibration loadings using the Tsai–Hill criterion. The vibration fatigue life can be estimated based on the rainflow amplitude probability density function p(S) of the equivalent stress, which is obtained from this PSD, combined with the S-N curve of the materials. The

Particleboards based on a mixture of grey alder (Alnus incana (L.) Moench) wood particles (sieve fraction 0.4-2 mm) and 15 or 25% of lignin powder obtained by hot pressing from four different industrial sources were investigated. Their density, thickness swelling, water absorption, modulus of rupture, modulus of elasticity in bending, and internal bond strength were determined. It was founded that

The paper presents a review of Haar wavelet methods and an application of the higher-order Haar wavelet method to study the behavior of multilayered composite beams under static and buckling loads. The Refined Zigzag Theory (RZT) is used to formulate the corresponding governing differential equations (equilibrium/stability equations and boundary conditions). To solve these equations numerically, the

The critical buckling load for a FGM plate under a linearly distributed in-plane load is determined. Material properties of the plate vary exponentially across its thickness. The Ritz method is used to solve the equations formed according to the 3D linear elasticity theory. The effects of different material compositions and dimensions of the plate on its critical buckling load and mode shapes are investigated

The effect of different frequencies on the glass-transition temperature, storage and loss moduli, and damping of untreated and sodium bicarbonate-treated sisal fibers reinforced biocomposites have been analyzed in the temperature range of 30-160°C. In addition, tensile and flexural properties of these composites were also studied as per ASTM standards. On the basis of the results obtained, it is concluded

In the paper, the averaging method was used to determine the effective elastic moduli of dispersed B4C/2024Al composites and porous geomaterials using 2D and 3D X-ray images of their internal structure. A comparison of calculated values of Young’s modulus with experimental data showed that the use of 2D models of the real structure led to underestimated values of Young’s modulus, especially for porous

The analytical solution of the bending problem for a clamped rectangular plate with a variable in-plane stiffness is found by using the method of superposition. The flexural rigidity of the plate varies across its width according to an exponential function. First, the analytical solution for a simply supported rectangular plate with a variable in-plane stiffness is obtained, and then the bending problem

A mathematical model and a technique for evaluating the technological process parameters to obtain superthin prepregs by flattening carbon tows impregnated with an epoxy binder have been developed. It is recommended to simultaneously roll 25-50 carbon tows containing 400-600 monofilaments by rolls 50-100 mm in diameter, which is conceptually and technically consistent with possibilities of the existing

The bending stiffness of carbon/epoxy and glass/epoxy cross-ply laminates with intralaminar cracks in the surface 90° plies and local delaminations were studied experimentally using 4-point bending tests. The bending stiffness is defined as the slope of the relation between the applied bending moment and the corresponding midplane curvature. To measure the midplane curvature of laminates with different

Two types of thin impact indicator films were developed: made of an epoxy composite with hollow glass microspheres and of a selfadhesive thermoplastic with retroreflective microprisms. They are highly sensitive to local impacts and change the intensity of light reflection in damage zones. Experimental investigations into the residual strength of a GFRP plate covered with indicator films and resting

A computational model describing crack formation in a fibrous composite is developed. It is assumed that, upon repeated loading, crack formation in the composite leads to its fracture. Determination of the unknown parameters characterizing an initial crack is reduced to solving a singular integral equation. A closed system of nonlinear algebraic equations whose solution allows one to predict crack

A dynamic analysis of the behavior of sandwich beams with a viscoelastic core under the action of a moving load is performed considering their geometrical asymmetry. The use of viscoelastic materials integrated into structures in front of the moving load is considered as a new suggestion to enhance their stability. A high-order theory, taking into consideration longitudinal and rotational inertias

The work presented is devoted to the axisymmetric contact problems on the interaction of a rigid stamp and an elastic layer fixed on a porous elastic half-space by using the Cowin–Nunziato model. It is assumed that the stamp basis has a flat or parabolic shape and friction is absent in the contact zone. With the help of the Hankel integral transform, the problems stated are reduced to solving integral

The application of asymmetric composite materials in such adaptive structures as fan blades, fixed-wing aircrafts, and tilting rotors can lead to more deformation modes and good mechanical properties still remaining hygrothermally stable. But the influence of the extension-bending coupling effect on their mechanical properties is unknown. The wing skin is taken as an example to obtain a variety of

Two optimization problems are formulated to improve the effectiveness and productivity of pultrusion processes, to preserve the quality of pultruded profiles, and to take into account the ambient industrial shop temperature and requirements of process technologists. To solve these problems, an optimization methodology using designed computer experiments and the response surface technique was developed

A progressive interlaminar damage model, based on the Northwestern University theory and a trapezoidal trilinear traction-separation law, is presented to predict the initiation and propagation of delamination in layered composites under Mode I and Mode II loadings. The capability and reliability of the damage model proposed is assessed by comparing its results with experimental data. It was found that

A photo-optical and radiophysical study into the destruction process of the internal structure of plexiglass (PMMA) after its exposure to an ionizing electron irradiation and a subsequent external mechanical point impact was carried out. Enlarged macrophotography of the picture of the radiation-mechanical internal destruction of plexiglass was performed at different shooting modes. An analysis and

During the curing process of thermoset composites, residual stresses inevitably develop in them and lead to their curing deformation after the manufacturing process. This work was aimed at investigating the effect of tool–part interaction and bending stiffness on the curing deformation of L-shaped composite structures. Therefore, a twostep calculation model was developed. It consists of a numerical

Electrorheological elastomers (EREs) have viscoelastic properties controllable by external electric fields. For their application, it is necessary to investigate the rheological properties of EREs under various loading conditions. In this work, anisotropic EREs based on a silicone rubber with 10 wt% of PI-Na polyimide particles oriented in an electric field were first obtained. Their elastic properties

Advances in the additive manufacturing (AM) processes have opened up the possibilities of widely using them in various structural sectors. Since 1980s this technology has been in permanent mutations. The ramification of the AM technology makes it difficult to obtain a clear impression of its potentialities. Predicting and controlling the mechanical characteristics of printed products is crucial for

The analytical solutions of supersonic flutter of porous functionally graded plates are investigated. The material properties of the plates (stiffness and density) vary according to a power law across the thickness and axial coordinates depending on the volume fraction of constituent materials. Their equilibrium and stability equations are derived based on the classical plate theory. The solution of

The static compression of porous aluminum specimens, with free vertical surfaces fixed in a cylindrical holder, was investigated both theoretically and experimentally. Calculation were performed using the principle of 3D similarity of the stress-strain state in structural elements of constructions. Such an approach allows one to take into account the nonuniform distribution of stresses and strains

The optimal stochastic distribution of carbon nanotubes (CNTs) in nanoreinforced polymer composite of a cantilevered microbeam is investigated. Finite-element simulations of the CNT-reinforced microbeams were conducted to obtain data for training an artificial neural network to construct a surrogate model. This model was then used in an optimization routine to determine the optimal CNT distribution

To model the deformation of fabric polymer composite materials highly nonlinear in tension along the warp/weft threads, an analytical approach is proposed. Based on experimental data and the method of a deformable polyhedron, a tool is developed for an efficient selection of parameters for the model of a fabric composite consisting of equivalent orthogonally stacked unidirectional layers. A new version

Based on the method of sampling surfaces, a hybrid finite-element model is developed for a three-dimensional analysis of laminated composite plates with piezoelectric patches. According to this method, the sampling surfaces inside the layers and piezoelectric patches parallel to the middle surface are selected, and displacements and electric potentials of these surfaces are introduced as unknown functions

Systems of equations are obtained to study the onset of panel flutter of a composite shell with a linearly varying thickness. Using a model developed, the critical flow-over speed, corresponding to the onset of flutter, as a function of thickness difference between the left and right ends of the shell is calculated for various values of the axial compressive force and shell length with and without

Based on the classical laminate theory and proceeding from the necessary and sufficient conditions for the hygrothermal stability of materials, interlayer hybrid extension-twisting coupled free-layer laminates are designed. Then, analytical solutions for their yield and buckling strengths are derived. A mathematical model for the optimum design of composite structure is established to realize a synchronous

Up to now, the notched strength of a composite laminate containing an inclined elliptical hole at its center has not yet been predicted by researchers due to the absence of an appropriate failure criterion and an analytical solution. In this study, this problem is tackled by using a finite-element-based procedure, developed previously by the authors, together with a modified point stress criterion

Reliable accelerated testing routines involving tests at enhanced temperatures are of paramount importance in developing viscoelastic models for polymers. The theoretical basis, the time-temperature superposition (TTS) principle, is used to construct master curves and temperature-dependent shift factor, which is the necessary information to simulate the material response in arbitrary temperature and

The design of composite structures is always a very delicate task to ensure that an antisymmetrically wound laminate had the performance required. Our study was carried out with the aim to optimize the performance/cost ratio of these materials. It consisted in the design and manufacture of orthotropic filament-wound glassreinforced polyester (GRP) pipes with different fiber orientation (± 45, ± 55

The internal friction spectra λ = f(T) and the temperature dependence ν = f(T) of the frequency of free damping in the temperature range from –150°C to 120°C of microwave-irradiated and nonirradiated samples of polyvinyl alcohol were obtained. A theoretical analysis of nature of the peak located on the ascending branch of the α-peak of relaxation losses on the internal friction spectrum is carried

The application of an artificial neural networks (ANN) to predicting the bending strength of a laminated veneer lumber (LVL) manufactured under different conditions is considered. First, experimental studies were conducted, and then an ANN model was developed based on the experimental data obtained. LVL specimens of walnut wood, glued with urea-formaldehyde resins containing a chemically modified starch

The fatigue damage evolution in glass-fiber-reinforced (GRP) mortar pipes under cyclic loading were investigated. Based on the results of fatigue tests, a two-stage linear law of stiffness degradation of a glass-fiber-reinforced plastic mortar pipe culvert is proposed, and a model for calculating its stiffness degradation is established. By proposing a reasonable residual stiffness calculating equation

In a geometrically linear formulation based on the use of variation principles of elasticity theory, the twodimensional equations of statics and the boundary conditions at the edge of an orthotropic bending plate are obtained within the framework of the classical theory and two low-order nonclassical theories: Reddy–Nemirovskii and Margueere–Timoshenko–Naghdi ones. It is shown that using the hypotheses

An attempt has been made to perform a comparative study on advances in the shear deformation theory for analyzing the statics and dynamics of different plates with the use of numerical examples. Initially, shape functions for the displacement field across the plate thickness are compared, and then, the stresses, deflections, and natural frequencies of laminated composite plates are also compared.

The influence of imperfect contact conditions between layers of a hollow sandwich sphere on its natural frequencies is studied. It is assumed that the materials of face layers are the same, but different from the core layer material. Each layer is made of a homogeneous isotropic material and has a constant thickness. Investigations are performed using a piecewise homogeneous body model with the use

A linear free vibration analysis is presented for computing the natural frequencies of a grid-stiffened carbon-nanotube-reinforced composite cylindrical shell. The carbon nanotubes (CNTs) are supposed to be oriented unidirectionally across the shell thickness, and the elastic moduli of the CNT-reinforced polymer composite are calculated using a modified rule of mixtures. In order to obtain the equivalent

The stochastic eigenvalue problem for free vibrations of functionally graded beams with a random elastic modulus is investigated. The effective material properties and beam cross section are assumed to vary continuously in different directions according to the exponential law. The governing equations for the natural frequency of the functionally graded beams are derived from Hamilton’s principle. In

For a carbon-fiber-reinforced plastic made of an ELUR-P unidirectional tape and an ХТ-118 cold-cure binder, specimens with a ±45° stacking sequence were tested for cyclic tension. The total axial strain was considered as the sum of nonlinearly elastic, viscoelastic, and irreversible creep strains. Using the Abel creep kernel, it was found that, at instants of time shifted by values multiples of the

The main features of physical modeling of the delamination growth rate in layered composites in tensile loading are considered. To estimate this rate, an equation in the form of the well-known Collipriest equation, which is widely used in estimating the crack growth rate in metal materials, is proposed. The values of empirical constants of the equation for a quasi-isotropic [45/90/-45/0]S XAS/914 carbon/epoxy

The hoop tensile strength of a composite pipe was measured experimentally using the split-disk test method. Then, a finite-element modeling was performed to simulate the split-disk test, and the progressive damage modeling was carried out to predict the maximum load the ring specimen representing the hoop tensile strength can carry. The progressive damage modeling was utilized in the context of continuum

A method for the ultrajet diagnostics of products made of composite materials is presented. It makes it possible to simulate, in an accelerated regime, the fatigue tests of materials and to estimate the adhesion strength of the fiber-filler bond under alternating loads. A hydroerosion model of the diagnosed surface under the operation of sequentially conjugate ultrajet actions by various working hydraulic

The improvement of Mode I fracture toughness of epoxy by the addition of single-walled carbon nanotubes (SWCNTs) is considered. To prepare nanocomposites, chemical-vapor-deposition-grown SWCNTs noncovalently functionalized with an ethoxylated alcohol was used as the additive and a diglycidyl ether of bisphenol-A-based epoxy as the matrix material. The SWCNTs were dispersed in the epoxy matrix via a

Structural models of hybrid fiber composites orthogonally reinforced in the plane are constructed. They allow one to calculate the yield loci taking into account the plane stress state in all composition components with different tensile and compressive yield stresses. Materials of the components are homogeneous and isotropic, and their mechanical behavior is described by the associated flow rule for

The role of fiber reinforcement architecture in adjusting the mechanical properties of glass-fiber-reinforced epoxy composite materials is studied. Fibrous E-glass unidirectional (UD) and 3-dimensional (3D) samples with an identical fiber volume fraction were prepared. The UD composites displayed excellent properties along the fiber direction, but the 3D ones showed excellent properties in all three

The static performance of a composite type 4 CNG cylinder was investigated using a finite-element simulation and experimental validation. This cylinder involved a liner hoop wrapped with a fiber impregnated by a suitable resin. Tensile tests were performed on standard specimens to examine the mechanical properties of the composite material. Next, a finite-element simulation was performed to determine

In a geometrically linear formulation based on the use of variational principles of elasticity theory and the generalized Galerkin method, three approaches to constructing equations of static bending of orthotropic plates with a constant thickness are considered. The displacements of plate points are approximated by polynomials in the transverse coordinate with unknown coefficients of expansion. The

The impact behavior of hybrid composite plates cured at 120°C were examined by dropping weights on them for three hours. Two groups of hybrid composite plates were considered. In the first group (TYPE1), all plies were staked symmetrically or antisymmetrically with orientation angle 0°, but in the second group (TYPE2), plies were staked symmetrically or antisymmetrically with orientation angles 0°

The effect of nanosize alumina (Al2O3) concentration on the morphology and mechanical properties of microfibrillar composites obtained by processing the thermodynamically incompatible polypropylene/ copolyamide (PP/CPA) blend was studied. It was established that composite monofilaments exhibited a selfreinforcing effect due to the in situ formation of PP fibrils (microfibers) in the CPA matrix. The

Drop-weight tests were conducted to investigate the impact responses of carbon-fiber-reinforced composite laminates under low-velocity impacts. A finite-element model is proposed to describe the failure during impacts. The impact damage behavior of composite laminates with different thicknesses were simulated to analyze their energy absorption ability, and a method for its prediction is presented.

Results of experimental investigations into a unidirectional composite of basalt fibers and epoxy resin used as part of high-voltage electric wires are presented. Tensile tests of BFRP specimens previously held wrapped around a transportation drum during 10 h were carried out. The influence of the keeping time of the BFRP core in the composition of a high-voltage electric wire on drums of diameter