Face Core Research Articles

Thermo-mechanical bending analysis of a sandwich cylindrical panel with an auxetic honeycomb core and GNP-reinforced face sheets

Thermo-mechanical bending analysis of a sandwich cylindrical panel with an auxetic honeycomb core and GNP-reinforced face sheets

External Moderation of Reactor Core Neutrons for Optimized Production of Ultra-Cold Neutrons

The ultra-cold neutron (UCN) source being commissioned at North Carolina State University’s PULSTAR reactor is uniquely optimized for UCN production in the former graphite-filled thermal column outside of the reactor pool. The source utilizes a remote moderation design, which is particularly well suited to the PULSTAR reactor because of its high thermal and epithermal neutron leakage from the core face. This large non-equilibrium flux from the core is efficiently transported to the UCN source through the specially designed beam port in order to optimize UCN production at any given reactor power. The increased distance to the source from the core also greatly limits the heat load on the cryogenic system. A MCNP (Monte Carlo N-Particle) model of this system was developed and is in good agreement with gold foil activation measurements using a test configuration as well as with the real UCN source’s heavy water moderator. These results established a firm baseline for estimates of the cold neutron flux available for UCN production and prove that remote moderation in a thermal column port is a valuable option for future designs of cryogenic UCN sources.

Nonlinear temperature dependent and visco-elastic foundation effects on the free vibration of functionally graded sandwich plates with ceramic foam core

This paper investigates the vibrations of a functionally graded sandwich plate (FG sandwich plate) with a ceramic foam core resting on a viscoelastic foundation. The focus is on the influence of temperature changes on sandwich plates that have foam core and FG face sheet on the free vibration. The damping coefficient and different schemes of sandwich plate have been considered in the current work. The analysis uses a quasi-3D theory, which reduces the number of unknown displacements and simplifies the equations by incorporating integral terms. Two models are employed to represent the non-uniformity of the ceramic foam core. To account for the influence of the supporting layer, a viscoelastic foundation is included. The governing equations are derived using Hamilton’s principle and solved using the Navier solution method. The paper comprehensively discusses how the volume fraction index k, geometric properties, ceramic foam distribution, viscoelastic foundation, and different temperature rise profiles impact the vibration response of the FG sandwich plate.

Investigating the effect of MXene reinforcement on the mechanical and vibrational behaviour of honeycomb core sandwich composite structures

Honeycomb core sandwich composite panels are now being employed in various industries and possess huge potential owing to the fact that they provide almost similar properties as that of traditional metallic materials with substantial reduction in weight and are extremely corrosion resistant. MXene nanosheets have caught attention of the scientific community owing their extraordinary physical, chemical and mechanical properties. In the present work, the effect MXene reinforcement on the bending and vibrational behaviour of honeycomb cored sandwich composite structures has been investigated using experimentation and finite element (FE) modeling. The honeycomb cored sandwich plates were fabricated and samples were tested via three-point bending and vibration test under various testing conditions. The SEM images revealed that the MXene nanosheets were well dispersed within the epoxy matrix when their mixture was prepared and the homogenous dispersion was also maintained in the fabricated honeycomb core. Also, the MXene and glass fibres were found to be well bonded with the matrix. As far as bending behaviour is concerned, the sandwich structure containing MXene reinforced honeycomb core displayed superior load bearing capacity and exhibited higher values of core shear strength and face sheet bending strength at all testing temperatures. Furthermore, the reinforcement of MXene resulted in an increase in the natural frequency for all the considered modes irrespective of the end conditions. For instance, the natural frequency of the honeycomb core sandwich composite plate at first mode increased by 5.5 % and 10.2 % under CFFF and CFCF boundary conditions, respectively, upon addition of MXene.

A finite element model for analyzing curved surface sandwich panel forming

The article establishes a finite element (FE) model of sandwich panel (referred to as CSC FE model) using shell structure core and solid structure face sheet and provides a detailed derivation of the data transfer process between the shell structure and the solid structure in the FE model. In order to explore the application of CSC FE model in the curved surface sandwich panel forming, this paper studies the single curvature and double curvature sandwich panel forming in detail. Based on the maturity of the three-point bending theory, in order to facilitate theoretical verification, the article chooses the three-point bending process to study the single curvature sandwich panels forming. It is proved that the CSC FE model can be effectively applied to single curvature sandwich panel forming through three-point bending theory, numerical simulations and experiments of brazed aluminum honeycomb panel (BAHP). Low cost and efficient multi-point forming (MPF) process is used to analyze the double curvature sandwich panel forming. By MPF experiments and numerical simulations of saddle-shaped and spherical BAHPs, and with the help of 3D laser scanning technology, it is proved that the CSC FE model can accurately predict the curved surface shape of double curvature sandwich panel forming.

A topology and sizing optimisation method for lightweight sandwich structures subject to dynamic and static constraints

A static-dynamic topology-sizing optimisation method is presented. The solution is based on a sequential Mixed-Integer Linear Programming solution and aims to minimise the mass of a structure subjected to concurrent constraints on static and dynamic response. It is shown that the classical problem of the dynamics of lightweight sandwich structures may be mitigated through core topology and face sheet thickness combinations, retaining the static load carrying capacity while presenting stringent dynamic properties at a low mass penalty.A numerical example, in the form of a load carrying sandwich beam which is excited at different frequencies, is used to demonstrate the method.

Characterization of the Core Face Irradiation Fixture at the Pennsylvania State University Breazeale Reactor

An efficient stacking method was applied to a multi-foil activation characterization of a core face fixture in Penn State’s TRIGA reactor using STAYSL PNNL software. The adjusted neutron energy spectra from the STAYSL PNNL software are in good agreement with the input MCNP models. The validated MCNP model was then used to predict the neutron energy spectrum within the core face fixture with a new lead shielding assembly in between the fixture and the core. Additional irradiation environment details such as the estimated gamma ray dose rates and sample temperatures provide a more comprehensive view of the core face fixture beyond the neutron energy spectrum, especially for more sensitive materials.

Empirical and numerical analysis of damage tolerance in multifunctional hybrid sandwich fiber reinforced polymers composite structures for aerospace applications using compression after impact (CAI) testing

AbstractThis study presents a novel hybrid‐sandwich composite structure, customized for nose radomes applications, incorporating a foam core and distinct opposite face sheets composed of Kevlar and S‐Glass materials. Addressing in‐phase electromagnetic properties, UV protection and low velocity impact responses in our previously published work, this paper empirically and numerically investigates the damage tolerance response of the proposed structures through compression after impact (CAI) testing. The low velocity impacts (LVIs) on S‐Glass face sheets exhibited unique energy dispersion and absorption mechanisms, resulting in variations in indent damage depths and widths across all impact energy levels as compared with LVIs on Kevlar face sheets. After experimentally assessing the CAI behavior, a FE model is developed to predict CAI behavior, which closely aligned with experimental findings. This study, unprecedented in existing literature, proposes hybrid sandwich structures for nose radome aerospace applications, with superior specific impact and residual strength compared to various composite sandwich structures documented in the published literature expanding its utility beyond radomes.Highlights Innovative composites with superior low velocity impact response, tested for compression after impact performance. Designed for nose radomes found suitable for other impact prone applications. Experimental and numerical modeling showed comparable results. Major differences observed in damage mechanics, resistance, and tolerances.

Hemispheric dominance in reading system alters contribution to face processing lateralization across development

Face processing dominates the right hemisphere. This lateralization can be affected by co-lateralization within the same system and influence between different systems, such as neural competition from reading acquisition. Yet, how the relationship pattern changes through development remains unknown. This study examined the lateralization of core face processing and word processing in different age groups. By comparing fMRI data from 36 school-aged children and 40 young adults, we investigated whether there are age and regional effects on lateralization, and how relationships between lateralization within and between systems change across development. Our results showed significant right hemispheric lateralization in the core face system and left hemispheric lateralization in reading-related areas for both age groups when viewing faces and texts passively. While all participants showed stronger lateralization in brain regions of higher functional hierarchy when viewing faces, only adults exhibited this lateralization when viewing texts. In both age cohorts, there was intra-system co-lateralization for face processing, whereas an inter-system relationship was only found in adults. Specifically, functional lateralization of Broca’s area during reading negatively predicted functional asymmetry in the FFA during face perception. This study initially provides neuroimaging evidence for the reading-induced neural competition theory from a maturational perspective in Chinese cohorts.

Elastic Foundation Solution for the End Notched Flexure (ENF) Mode II Sandwich Configuration

Abstract This paper presents a closed form solution for the energy release rate of face/core debonds in the Mode II end notched flexure (ENF) sandwich configuration. The finite-length sandwich specimen is considered to have a “debonded” region and a “joined” region. In the later, the interface between the top face and the substrate (core and bottom face) is modeled by an elastic foundation, which is a uniform distribution of shear and normal springs. Based on the Timoshenko beam theory, the solution for a general asymmetric sandwich construction is derived. The energy release rate expression is derived via the J-integral. Another closed form expression for the energy release rate is derived from the energy released by a differential spring as the debond propagates. In this closed form solution there is no fitting and everything, including the foundation constants, are given in closed form. Results are produced for a range of face/core stiffness ratios and debond length/core thickness ratios, and are compared with the corresponding ones from a finite element solution. A very good agreement is observed except for small debond lengths vs specimen thickness.

Three-dimensional thermomechanical wave propagation analysis of sandwich nanoplate with graphene-reinforced foam core and magneto-electro-elastic face layers using nonlocal strain gradient elasticity theory

This article investigates the propagation of bending, longitudinal, and shear waves in a smart sandwich nanoplate with a graphene platelet (GPL)-reinforced foam core and magneto-electro-elastic (MEE) surface layers using sinusoidal higher-order shear deformation theory (SHSDT). The suggested nanoplate is comprised of a Ti–6Al–4V foam core placed between MEE surface layers. The MEE surface layers are composed of a volumetric combination of cobalt-ferrite (CoFe2O4) and barium-titanate (BaTiO3). The foam core and MEE face layers’ material characteristics are temperature dependent. In this study, three different core types are considered: metallic solid core (Type-I), GPL-reinforced solid core (Type-II) and GPL-reinforced foam core (Type-III), as well as three different foam distributions: symmetrical foam I (S-Foam I), symmetrical foam II (S-Foam II) and uniform foam (U-Foam). To derive the nanoplate's equations of motion and determine the system response, Hamilton's principle and Navier's method are employed. The effects of various parameters such as the wave number, nonlocal parameter, foam void coefficient and distribution pattern, GPL volume fraction, and thermal, electric, and magnetic charges, on the phase velocity and wave frequency are investigated via analytical calculations. The findings of the research indicate that the 3-D wave propagation characteristics of the sandwich nanoplate can be considerably modified or tuned with respect to external loads and material parameters. Thus, the proposed sandwich structure is expected to provide important contributions to radar stealth applications, protection of nanoelectromechanical devices from high frequency and temperature environments, advancement of smart nanoelectromechanical sensors characterized by lightweight and temperature sensitivity and wearable health equipment applications.

Frequency Assessment of Sandwich Rectangular Plates with an Anisogrid Core and GPLRC Face Sheets

Frequency Assessment of Sandwich Rectangular Plates with an Anisogrid Core and GPLRC Face Sheets

Temperature self-compensated fiber-optic Pb(II) sensor with improved selectivity by Resorcylaldehyde post-modified organic metal framework

Post-modification of metal-organic framework (MOF) materials is an effective means to enhance their efficient and selective adsorption for heavy metal ions. In this article, we presented a reflection-type optical fiber surface plasmon resonance (SPR) sensor based on dual core fiber (DCF) coated with UiO-66-RSA (UiO-66-NH2 post-modified with resorcinol aldehyde) film for the specific detection of Pb(II) in aqueous media. The composite material UiO-66-RSA exhibits stronger affinity and specificity for Pb(II) than UiO-66-NH2. The adsorption of Pb(II) can change the equivalent refractive index (RI) of UiO-66-RSA film, causing a regular shift in SPR spectra. Experiments have shown that the limit of detection (LOD) of the SPR Pb(II) sensor can reach 0.1 nM. Meanwhile, research has found that the SPR sensor is accompanied by temperature crosstalk of 0.356 nm/°C. Therefore, we constructed a Michelson temperature interferometer using polymer micro tips on the end face of the fiber core to achieve temperature compensation. Based on the above two sensing channels, dual parameter demodulation of Pb(II) concentration and temperature can be achieved with an error rate of less than 0.5 %. This article has potential research value in exploring the application of post modification techniques of MOF in fiber optic lead ion detection.

Response of the orthogonal corrugated sandwich panel under low-velocity impact with different shaped impactors

This study aims at investigating the low-velocity impact resistance of the composite orthogonal corrugated sandwich panel through experimental and simulation methods, considering different shaped impactors. To that scope, the progressive damage model with the sandwich panel is developed and numerical investigations are carried out in ABAQUS / Explicit. The results show that as the impactor changes from flat to hemispherical and then to conical shape, the first peak load gradually decreases, and the maximum displacement of the impactor and total energy absorption gradually increase. The high impact energy makes the sandwich panel more compliant. Furthermore, the expansion area of fiber damage, matrix damage and delamination in the top face sheet, core and bottom face sheet depends on the impactor shape and impact energy. Under high impact energy, the damage under the conical impactor mainly expands along the thickness direction of the sandwich panel rather than in the in-plane direction, while the flat impactor causes large damage area in the in-plane direction as well.

Vibration characteristics of a cylindrical sandwich shell with an FG auxetic honeycomb core and nanocomposite face layers subjected to supersonic fluid flow

In this paper, the flutter analysis is studied for a cylindrical sandwich shell subjected to external supersonic fluid flow. The sandwich shell consists of a re-entrant auxetic honeycomb (AH) core made of functionally graded materials (FGMs) which is covered with two polymeric face layers enriched with either carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), or graphene oxide powders (GOPs). The volume fraction (percentage) of the ceramic phase in the functionally graded auxetic honeycomb (FGAH) core varies from zero at the inner surface to one at the outer one based on either power-law function (P-FGM), exponential function (E-FGM), or sigmoid function (S-FGM). It is assumed that the nanofillers are distributed uniformly inside the face layers. The first-order shear deformation theory (FSDT) and the piston theory are employed to provide the mathematical models of the shell and the aerodynamic pressure, respectively. The governing equations and boundary conditions are derived via Hamilton’s principle. An exact solution is performed in the circumferential direction via harmonic trigonometric functions (sine and cosine) and an approximate solution is performed in the axial direction utilizing the differential quadrature method (DQM). The natural frequencies and corresponding damping ratios are attained through the presented semi-analytical solution and the impacts of several factors on the natural frequencies and the critical aerodynamic pressure of the shell are examined. These factors the type of the FGM, the material index, and inclined angle of the cells in the FGAH core, the thickness of the FGAH core, the type and mass fraction of the nanofillers in the nanocomposite face layers, and boundary conditions.

Temperature-dependent thermal buckling and free vibration behavior of smart sandwich nanoplates with auxetic core and magneto-electro-elastic face layers

This article addresses the thermomechanical thermal buckling and free vibration response of a novel smart sandwich nanoplate based on a sinusoidal higher-order shear deformation theory (SHSDT) with a stretching effect. In the proposed sandwich nanoplate, an auxetic core layer with a negative Poisson’s ratio made of Ti-6Al-4V is sandwiched between Ti-6Al-4V rim layers and magneto-electro-elastic (MEE) face layers. The MEE face layers are homogenous volumetric mixtures of cobalt ferrite (CoFe2O4) and barium titanate (BaTiO3). The mechanical and thermal material properties of the auxetic core and MEE face layers are temperature-dependent. Using Hamilton’s principle, governing equations are constructed. To characterize the size-dependent behavior of the nanoplate, governing equations are adapted with the nonlocal strain gradient theory (NSGT). By applying the principles of Navier’s technique, closed-form solutions are obtained. Parametric simulations are carried out to examine the effects of auxetic core parameters, temperature-dependent material properties, nonlocal parameters, electric, magnetic, and thermal loads on the free vibration and thermal buckling behavior of the nanoplate. According to the simulation results, it is determined that the auxetic core parameters, temperature-dependent material properties, and nonlocal factors significantly affect the thermomechanical behavior of the nanoplate. The outcomes of this investigation are expected to contribute to the advancement of smart nano-electromechanical systems, transducers, and nanosensors characterized by lightweight, exceptional structural integrity and temperature sensitivity. Also, the auxetic core with a negative Poisson’s ratio provides a metamaterial feature, and thanks to this feature, the proposed model has the potential to be used as an invisibility technology in sonar and radar-hiding applications.

In-Plane Vibrations of Deep Sandwich Arches with Different End Conditions Based on a Logarithmic Shear Deformation Theory

This paper deals with the vibrational frequencies of deep sandwich arches to enhance their application domain and possibly use them for energy harvesting. The circular arch with porous nanocomposite core and titanium alloy face sheets having different end conditions is numerically analyzed. The middle core of the sandwich arch is made of a six-layered porous aluminum reinforced with graphene nanoplatelets. The kinematic equations are formulated in this study based on the higher-order shear deformation theory using a logarithmic function of radius. The effective properties of the nanocomposite media are modeled by employing the Halpin–Tsai modified rule. The equations of motion are determined by applying the principle of virtual displacement. The partial differential equations are reduced using the generalized differential quadrature technique to solving an algebraic eigenvalue problem. Novel numerical results are given to show the effects of geometrical parameters, material properties, and boundary conditions on the vibrations of deep sandwich arch.

Efficient design of composite honeycomb sandwich panels under blast loading

Hybrid composite honeycomb sandwich structures (HCHSS) were employed due to high specific strength and stiffness and higher impact resistance property required for the aerospace and defence fields. The numerical modelling of the efficient HCHSS was developed for the core, front and back face plate using the C3D8R elements to determine the realistic failure behaviour for the honeycomb sandwich structure. The ConWep blast simulation loading was applied for the HCHSS. Advanced composite materials were used for the blast analysis of the HCHSS (carbon/epoxy, graphite/epoxy, woven basalt fibres/polypropylene and woven Kevlar fibres/polypropylene). The damage initiation and damage propagation based progressive damage modelling was developed and implemented in the VUMAT code for composite materials to determine the actual failure behaviour of the HCHSS. The face sheets used in this model were of a stainless-steel alloy AL-6XN. The sandwich structure was subjected to blast loads of 1, 2 and 3 kg of TNT and their performance was compared w.r.t both front and back-face deflection. The effectiveness of sandwich panels was further examined by altering the thickness of the core. Fibre-metal laminates (FML) were used in place of the steel face sheets in the panel in order to minimise its mass, and a thorough analysis of the panel’s mass in relation to its peak deflection was carried out. Upon analysing the results, it was noted that the panel with the basalt fibre reinforced polymer (BFRP) core gave the best results compared to other composite materials. For a blast load of 3 kg TNT, the peak back face deflection (PBFD) of HCHSS with a BFRP core decreased by 10.64%, 7.61% and 4.75%, respectively, compared to panels with CFRP, GFRP, and KFRP cores. The peak deflection of the panel decreased as the BFRP core thickness increased. The energy absorption capacity of the panel also increased with increasing thickness. Additionally, it was found that panels with BFRP cores and KFRP-steel laminate face sheets provided the optimum balance of strong blast resistant performance and light weight. Compared to the metallic (steel) sandwich panel, the mass of the sandwich panel with KFRP-steel laminate face sheets and BFRP core was reduced by 33%, but at the same time, its PBFD increased by almost 50%.

Experimental study on resin pin-reinforced marine sandwich composites under quasi-static indentation load

This study aims to experimentally examine the indentation behaviour of marine sandwich composites with pin-reinforced polyvinyl chloride foam core and E-glass face sheets. The effects of indenter diameter, resin pin diameter, and arrangement on force-displacement, maximum contact force, and absorbed energy values of sandwich panels were evaluated by the indentation tests. Throughout the experiments, the contact forces increased as the pin diameter increased. The contact forces reduced as the distance between pin diameters increased. Additionally, the values of absorbed energy increased as the diameters of the resin pin and indenter increased. Placing the pins more closely together additionally allows the material to absorb more energy in the event of indentation. A visual inspection took place on the post-indentation cross-sections of the sandwich specimens to detect any damage modes. Damage modes varied depending on the size of the indenter and the hole pattern in the foam core.

The assessment of electric voltage influence on vibrational behavior of intelligent sandwich plates with GO-reinforced metal foam core and piezoelectric actuator face sheets

In this research, it is tried to study the effect of the external electric voltage on the vibrational behavior of a smart sandwich plate made of graphene oxide-strengthened metal foam nanocomposite core and two piezoelectric face sheets for the first time. The sandwich plate is modeled utilizing first-order shear deformation theory. The effective material properties of the core layer are estimated with the aim of the blend of Halpin-Tsai micromechanical model and rule of the mixture while considering different graded graphene oxide distribution patterns. Additionally, various porosity distributions are regarded in the metal matrix of the core layer. The partial differential equations of motion are derived using Hamilton’s principle and the derived governing equations are solved through Navier’s solution. To perform an accurate verification, the obtained results are compared with different literature investigations. Afterward, the influence of various important variants including external electric voltage, aspect ratio of plate, core to face sheet thickness ratio, different porosity distribution patterns, porosity coefficient, nanofillers weight fraction, and various distribution patterns of graphene oxides on the dimensionless frequency of smart sandwich plate in the framework of a group of tables and figures.