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The advantages of carbon nanotubes (CNTs) in fortifying the glass fiber reinforced polymeric (GFRP) composites are discussed in this paper. Bolted steel straps are utilized at the edges of composite plate to establish clamped conditions in the test setup. To minimize uncertainties caused by bolt attachments, a genetic algorithm-based model updating approach has been implemented by introducing artificial linear springs at the margins to achieve a better balance between theory and reality. The accuracy of the plate's results (natural frequencies and mode shapes) is verified, and the mechanical properties of randomly dispersed CNTs are incorporated in the formulations of folded plates. Remarkably, the motion equations are brought forward by the first order shear deformation theory (FSDT). Thereafter, two-directional generalized differential quadrature (2D-GDQ) technique is employed to determine natural frequencies from available motion, continuity, and boundary equations. The results of the folded plate are validated first by an experimental modal testing and finally some effective parameters such as folding angle, CNT weight ratio, boundary condition and flange-shape length are examined. [ABSTRACT FROM AUTHOR]

This paper presented a systematic approach toward localized failure inspection of internally pressurized laminated ellipsoidal woven composite domes. The domes were made of thin glass fiber reinforced polymer (GFRP) woven composite layups [0,0,0], [0,30,0], [0,45,0], and [0,75,0]. The analytical results demonstrated that the circumferential regions near meridian φ = 45° in prolate ellipsoidal domes and near meridian φ = 90° in oblate ellipsoidal domes sustain the highest deformation under internal pressure. This observation was then confirmed by the numerical and experimental results. In addition, the numerical and experimental results showed localized rather than uniform failure in those regions, irrespective of changes in laminate stacking sequence. It was observed that localized failure occurs since the woven fibers configuration in some areas of woven remains in initial geometry (square shape), while the rests are deformed into the rhombic shape. In other words, by moving along the circumferential direction from the area close to θ = 0° to θ = 45° and θ = 45° to θ = 90°, the shape of woven fibers gradually changes from square (strong area) to rhombic (weak area), and rhombic to square, respectively. Thus, to minimize failure pressure, the meridian region vulnerable to failure must initially be identified. Afterwards, the rhombic regions in the circumference corresponding to that meridian must be strengthened. [ABSTRACT FROM AUTHOR]

The subject of this paper are thin composite rectangular plate. The plates are made of two families of ribs and homogeneous material of a matrix. The main feature of the considered plates is, that a distance between the ribs is comparable to the thickness of the plate. The widths of the ribs can vary slowly in the midplane of the plate. This allows you to get a desirable frequency of natural vibrations of the plate. The formulation of averaged model equations is based on the tolerance averaging approach (Wozniak et al. 2008, 2010). The general results of the contribution are illustrated using the analysis of natural vibrations of the plates under consideration. It will be carried out validation of the obtained mathematical model by comparison of results from obtained model equations with results from finite elements method (Abaqus program). [ABSTRACT FROM AUTHOR]

Low-velocity impact damaging of the composite structural elements is an important problem during machine's operation, especially in the aircraft and aerospace industries. Thus, appropriate nondestructive structural diagnostics methods should be developed in order to identify the damages in possible early stage of their development. The paper deals with the experimental study of impact damage identification of composite structures subjected to the low-velocity impacts by stones. The proposed damage identification algorithm is based on the modal analysis of damaged structures and further wavelet analysis of acquired modal shapes using nonseparable quincunx wavelets. The analysis was performed for the composite structures typical for those used in the aeroplane sheeting impacted with various energies. The application of quincunx wavelets allows for accurate localization of the damages and for avoiding the boundary effect occurred during an application of separable wavelets. Obtained results show the efficiency of the proposed method and could be used in industrial applications as well. [ABSTRACT FROM AUTHOR]

This article performs an analytical study on the damping vibration behavior of metal foam nanocomposite plate reinforced with graphene oxide powders (GOPs) in thermal environment. The GOPs are dispersed through the thickness of the structure according to three functionally graded (FG) and one uniform distribution patterns. The Halpin–Tsai micromechanical model is chosen for estimating the effective material properties of the structure having GOPs as reinforcement phase. Also, different porosity types are taken into account for the metal foam matrix. The plate is resting on a three-parameter viscoelastic medium containing Winkler and Pasternak layers in combination with viscous dampers which can dissipate the oscillation of the structure in some special cases. The Governing differential equations are derived via Hamilton's principle on the basis of refined higher order shear deformation theory and then solved with employing Galerkin solution method to obtain the natural frequencies of the proposed structure. Moreover, various boundary conditions (B.Cs) including simply supported, fully clamped and different combinations of these B.Cs are considered in this study. The influences and confrontation of different significant parameters such as GOPs' weight fraction, foundation parameters, aspect and side-to-thickness ratios, porosity coefficients, thermal environment, and FG patterns are investigated through various graphical and numerical results. Our findings declare that the dynamic behavior of the graphene oxide powder reinforced metal foam (GOPRMF) plate remarkably depends on these parameters. [ABSTRACT FROM AUTHOR]

A new theoretical solution is presented to determine the stress distribution in a ten-layer simply-supported circular composite plate subjected to the low-velocity impact. The aim of the current study is the investigation of the dynamic analysis of the composite plate when a cylindrical impactor hits the top layer of the plate with an initial velocity of 1 m/s. The plate is made of two adhesive layers adhere two aluminum layers to a six-layer carbon-epoxy laminated plate. The classical non-adhesive elastic contact theory and Hunter's relationship are used to simulate the contact behavior in terms of time and contact radius. By using Hamilton's principle and Layerwise theory, thirty-two equations of motion are derived. Moreover, Johnson–Cook's criteria, the plastic simulation model, the normal stress–strain failure criterion theory were used for failure analysis of the aluminum, adhesive, and carbon-epoxy layers, respectively. The numerical method was used to solve the thirty-two differential equations of motion based on the finite difference method. Moreover, the relationship between stress and strain is re-written in the numerical code so that the failure criterion theories are satisfied. Moreover, according to the defined failure criterion for each layer, the damage is checked at the end of every time step. In addition, the damping behavior of the composite plate after applying the contact pressure caused by the impact was also investigated. The results showed that the impact resulted in residual stress in the plate. [ABSTRACT FROM AUTHOR]