Nanocomposite Panels Research Articles

Advanced Radar Absorbing Ceramic-Based Materials for Multifunctional Applications in Space Environment.

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses.

Impact Deformation of Curved Nanocomposite Panels

In this study, low-velocity impact response of cylindrically curved bilayer panels is studied. A large number of parameters affect the impact dynamics, and many models have been used previously; these models can be classified as energy-balance model; spring–mass model and complete models in which the dynamic behavior of the structure is exactly modeled. In this study, a spring–mass model is used to evaluate the displacement response of curved panel. This work uses modified Hertz contact model which is linearized form of general Hertz contact law. Fourier series expansion is used to derive the governing equations of panel. In this paper, the effects of panel curvature and mass of impactor on the shell behavior under low-velocity impact are investigated. The results show that changing the panel radius of curvature will change the panel deformation. A numerical simulation analysis is used for result validation, and the results are compared to analytical model.

Experimental and numerical analysis of impact on curved nanocomposite panels

ABSTRACTIn this work nanopolyurea is used as reinforcement for curved steel plates under low velocity impact loading. Experimental and numerical analysis are used to study the effect of plate curvature and nano particle effects. A drop weight test apparatus is utilized to apply impact loading on bi-layer panels. Experiments show that maximum improvement in energy absorption capacity of nanopolyurea is about 5%. Numerical analysis is carried out using explicit LS-DYNA solver. The results show that by increasing panel radius of curvature, impact force increases; also comparison between numerical and experimental results shows a good agreement.

Uncertainty propagation in vibrational characteristics of functionally graded carbon nanotube-reinforced composite shell panels

Understanding the effect of mechanical uncertainties can play a significant role in design of the nanocomposites. The uncertain natural frequencies of moderately thick doubly-curved functionally graded composite panels reinforced by carbon nanotube (CNT) are investigated. Specifically, doubly-curved shell panels, including spherical, cylindrical and hyperbolic paraboloid panels are examined. To evaluate uncertainty propagation, uncertainty resources including distribution of the CNT through the thickness as well as the mechanical properties of the CNT and polymer matrix are taken into consideration. To assess the propagated uncertainties in the vibrational characteristics of nanocomposite panels, the interval analysis method is employed while the mechanical properties of nanocomposite panels are predicted using the modified rule of mixture method. Based on the comparison between the results of the present study and those reported in the literature, the accuracy of the results is validated. The sensitivity analysis is performed to distinguish the most prominent uncertain variables. Furthermore, numerical results reveal the influences of various uncertainty resources on the upper and lower bounds of uncertain frequencies and uncertainty propagation percent.

Influence of nanoclay on mechanical and thermal properties of glass fiber reinforced polymer nanocomposites

A novel approach was carried out to evaluate the effects of nanoclay in nanocomposite laminates based on mechanical properties, thermal analysis, and surface structure analysis. The composite panel was fabricated by reinforcing glass fiber with epoxy resin. Likewise, nanocomposite panels were fabricated by reinforcing glass fiber with nanoclay loaded epoxy. The loading of Cloisite 25A nanoclay in epoxy resin is varied as 2%, 4%, 6%, 8%, and 10% on weight basis. Upon completion of curing, the composite panel and nanocomposite panels were fabricated by using compression molding. The tensile test exhibited that the addition of nanoclay in epoxy resin has improved the tensile strength and Young's modulus by 33.39% and 15.88%, respectively for 2 wt% clay loading laminates than unfilled laminate. Likewise, the greater flexural strength of 438.04 MPa and flexural modulus of 22.12 GPa were attained for 2 wt% nanoclay/epoxy nanocomposite. The thermal results disclosed that greater thermal stability was attained between temperatures ranges from 0°C to 180°C for low clay content. The surface morphology too proved that the prepared laminates of 2 wt% loading exhibited appreciable surface property. POLYM. COMPOS., 39:1861–1868, 2018. © 2016 Society of Plastics Engineers

Vibration analysis of the embedded piezoelectric polymeric nano-composite panels in the elastic substrate

Abstract In the present study the vibrations of a smart thin micro panel of polymeric nano-composite reinforced by the Single-Walled Boron-Nitride Nano-Tubes (SWBNNTs) and the matrix Poly-VinyliDene Fluoride (PVDF) on an elastic substrate is studied. Using the micromechanics method, the nano-composite structural equations are obtained for a sample volume element and by considering a unidirectional electric field and stress in the field. The stress-strain relationships that include mechanical and electric terms are obtained for the micro-tubes. The micro-panel is considered as the thin wall shell and Donnell’s non-linear theory is used for the strain-displacement relations. To obtain the equations of motion, the minimum energy method or Hamilton’s principle is used. The external work is caused by the elastic environment as well as the magnetic field energies. Given that the work has been in small micro scale the strain gradient, modified coupled stress and classic theories are used to consider the small-scale effect in the equations. The results showed Stiffness of the panel is reduced by increasing length and reducing volume fraction of BNNT and lower frequencies are obtained. Angling nanotubes is reduced panel frequency and the severity of this reduction is increased at higher volume percentages. The maximum frequency is happened in the full cylinder sector.

Frequency analysis of doubly curved functionally graded carbon nanotube-reinforced composite panels

Vibration characteristics of moderately thick doubly curved functionally graded composite panels reinforced by carbon nanotube are analyzed. Here, special cases of doubly curved shell panels such as spherical, cylindrical and hyperbolic paraboloid panels and five different distributions of carbon nanotubes through the thickness direction are considered. By utilizing the modified rule of mixture, mechanical properties are estimated. The equations of motion are derived via the first-order shear deformation theory, and non-dimensional frequencies are obtained by the use of Galerkin’s method. The suggested model is justified by a good agreement between the results given by present model and available data in the literature. The influences of volume fraction of carbon nanotubes, thickness ratio, aspect ratio, curvature ratio, and shallowness ratio on the frequencies of moderately thick doubly curved nanocomposite shell panels are also examined. Furthermore, the effect of various boundary conditions on the frequency analysis of doubly curved nanocomposite panels is studied, and the corresponding mode shapes are depicted.

3D free vibration analysis of elastically supported thick nanocomposite curved panels with finite length and different boundary conditions via 2D GDQ method

ABSTRACTBased on the three-dimensional theory of elasticity, free vibration characteristics of nanocomposite panels reinforced by randomly oriented, straight, single-walled carbon nanotubes (SWCNTs) are considered. The volume fractions of randomly oriented agglomerated SWCNTs are assumed to be graded not only in the radial direction but also in the axial direction of the curved panel. This study presents a 2D six-parameter power-law distribution for CNTs volume fraction of 2D continuously graded nanocomposite that gives designers a powerful tool for flexible designing of structures under multi-functional requirements. The material properties are determined in terms of local volume fractions and material properties by the Mori-Tanaka scheme.

Postbuckling of pressure-loaded nanotube-reinforced composite doubly curved panels resting on elastic foundations in thermal environments

This paper presents an investigation on the postbuckling behavior of doubly curved nanocomposite panels reinforced by carbon nanotubes (CNTs) subjected to lateral pressure. The functionally graded carbon nanotube-reinforced composites (FG-CNTRCs) are assumed to have CNTs linearly graded in the thickness direction. The overall mechanical properties of the FG-CNTRCs, which include the thermal effect of CNTs and the matrix, are estimated through a micromechanical model. The panels may rest on elastic foundations. The governing differential equations for the doubly curved panels are based on a higher order shear deformation shell theory with von Kármán strain–displacement relationships and the panel–foundation interaction. The initial deflections caused by lateral pressure and thermal bending stresses are both taken into account. The governing equations are further deduced to a boundary layer type problem that includes nonlinear prebuckling deformations and initial geometric imperfections of the panels which are subsequently solved using a two-step perturbation approach. The influences of CNT volume fraction, temperature variation, panel geometric parameters, as well as foundation stiffness on the postbuckling behavior of FG-CNTRC doubly curved panels are investigated.

Large amplitude free vibration of nanotube-reinforced composite doubly curved panels resting on elastic foundations in thermal environments

A large amplitude vibration analysis is presented for nanocomposite doubly curved panels resting on elastic foundations in thermal environments. The doubly curved nanocomposite panels are studied with the consideration of different types of distributions of uniaxial aligned single-walled carbon nanotubes (SWCNTs). The material properties of the functionally graded carbon nanotube-reinforced composites (FG-CNTRCs) are assumed to be graded in the thickness direction according to linear distributions of the volume fraction of CNTs and are estimated through a micromechanical model. The motion equations are based on a higher order shear deformation theory and von Kármán strain-displacement relationships. The thermal effects are also included and the material properties of CNTRCs are assumed to be temperature-dependent. The motion equations are solved by a two-step perturbation approach to determine the nonlinear frequencies of the CNTRC doubly curved panel. The numerical illustrations cover small- and large-amplitude vibration characteristics of CNTRC doubly curved panels resting on Pasternak elastic foundations. The present solutions also highlight the effects of CNT volume fraction, temperature variation, foundation stiffness, panel curvature ratio as well as in-plane boundary conditions on the nonlinear free vibration behaviors of CNTRC doubly curved panels.

Vibration and nonlinear dynamic response of imperfect three-phase polymer nanocomposite panel resting on elastic foundations under hydrodynamic loads

An investigation on the nonlinear dynamic response and vibration of the imperfect laminated three-phase polymer nanocomposite panel resting on elastic foundations and subjected to hydrodynamic loads is presented in this paper. The formulations are based on the classical shell theory and stress function taking into account geometrical nonlinearity, initial geometrical imperfection and Pasternak type elastic foundation. Numerical results for dynamic response and vibration of the three-phase polymer composite panel are obtained by Runge–Kutta method. The influences of fibers and particles, material and geometrical properties, foundation stiffness, imperfection and hydrodynamic loads on the nonlinear dynamic response and nonlinear vibration of the three-phase composite panel are discussed in detail.

Characterization of synthesized polyurethane/montmorillonite nanocomposites foams

Nanophased hybrid composites based on polyurethane/montmorillonite (PU/MMT) have been fabricated. The nanocomposite which was formed by the addition of a polyol premix with 4,4'-diphenylmethane diisocyanate to obtain nanophased polyurethane foams which were then used for fabrication of nanocomposite panels has been shown to have raised strength, stiffness and thermal insulation properties. The nanophased polyurethane foam was characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM) measurements and X-ray diffraction (XRD). TEM and SEM analysis indicated that nanophased particles are dispersed homogeneously in the polyurethane matrix on the nanometer scale indicating that PU/MMT is an intercalated nanocomposite with a 2-3 nm nanolayer thickness.

Nanofillers modification of Epocast 50-A1/946 epoxy for bonded joints

Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes (MWCNTs), SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages. The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.

Dynamic stability analysis of carbon nanotube-reinforced functionally graded cylindrical panels using the element-free kp-Ritz method

In this paper, a first-known dynamic stability analysis of carbon nanotube-reinforced functionally graded (CNTR-FG) cylindrical panels under static and periodic axial force by using the mesh-free kp-Ritz method is presented. The cylindrical panels are reinforced by single-walled carbon nanotubes (SWCNTs) with different types of distributions, i.e. uniform and three kinds of functionally graded distributions of carbon nanotubes along thickness direction of the panels. Eshelby–Mori–Tanaka approach is employed to estimate effective material properties of the resulting nanocomposite panels. By applying the Ritz minimization procedure to the energy expressions, a system of Mathieu–Hill equations is formulated. Then the principal instability regions are analyzed through Bolotin’s first approximation. Detailed parametric studies have been carried out to reveal the influences of volume fraction of carbon nanotubes, edge-to-radius ratio and radius-to-thickness ratio. In addition, effects of different boundary conditions and types of distributions of carbon nanotubes are examined in detail.

Static and dynamic of carbon nanotube reinforced functionally graded cylindrical panels

The analysis of flexural strength and free vibration of carbon nanotube reinforced composite cylindrical panels is carried out. Four types of distributions of uniaxially aligned reinforcements are considered, i.e. uniform and three kinds of functionally graded distributions of carbon nanotubes along thickness direction of the panels. Material properties of nanocomposite panels are estimated by employing an equivalent continuum model based on the Eshelby–Mori–Tanaka approach. The governing equations are developed based on the first-order shear deformation shell theory. Detailed parametric studies have been carried out to reveal the influences of volume fraction of carbon nanotubes, edge-to-radius ratio and thickness on flexural strength and free vibration responses of the panels. In addition, effects of different boundary conditions and types of distributions of carbon nanotubes are examined.

Intermediate velocity bullet impact response of laminated glass fiber reinforced hybrid (HEP) resin carbon nano composite

In this study, five different types of six layered GFRP laminates were prepared from three types of resin systems and compared for their intermediate velocity bullet impact response. The first panel was made of epoxy resin, second one is of hybrid resin (a blend of 60% epoxy and 40% polyester) and the remaining three panels were made of hybrid resin with MWCNT in three different proportions by weight (0.1%, 0.5% and 1.0%). The composite and nano-composite panels were characterized experimentally for the important issues in the field of aerospace engineering, like medium velocity bullet impact response and vibration damping characteristics. The MWCNTs were responsible for greater characteristics improvement in the hybrid resin due to their high tendency to absorb the impact shock. The panels without MWCNT turn out to be lesser shock absorption capability. Additionally, 0.1% MWCNT hybrid panel shows exceptional damping response by damping the impacted vibration within 9.5 ms. There is also a 175.51% increase in the damping ratio of the panel. The higher percentage MWCNTs show lesser response towards damping of vibration. This may be due to the lengthy entangled structure of MWCNTs in the resin. It is also observed that the impacted damage is higher in the epoxy system panel than the nano-composite panel.

Effect of preshearing on the structure and properties of poly(methyl methacrylate)/clay nanocomposite panels

AbstractThe effect of preshearing resin mixtures prior to casting on the structure and properties of in situ polymerized poly(methyl methacrylate)/clay nanocomposite panels was investigated. The preshearing was performed with a mechanical stirrer and controlled by varying mixing time. The structure, thermomechanical, and optical properties of the panels prepared with different preshearing times were analyzed by XRD, TEM, DMA, and UV/visible spectrophotometer. The properties of the panels increased with preshearing time because of improved intercalation and exfoliation of the clay. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008