Hexagonal Core Research Articles

Light-triggered multifunctional nanoplatform for efficient cancer photo-immunotherapy

Cancer immunotherapy is limited by the immune escape of tumor cells and adverse effects. Photo-immunotherapy, the combination of immunotherapy and phototherapy (such as photodynamic therapy (PDT) and photothermal therapy (PTT)), can improve the effectiveness of immunotherapy in cancer treatment. Here, we first explored mesoporous hexagonal core–shell zinc porphyrin-silica nanoparticles (MPSNs), which are composed of a zinc porphyrin core and a mesoporous silica shell, and exhibit high laser-triggered photodynamic and photothermal activity, as well as outstanding drug loading capacity. In other words, MPSNs can be used not only as excellent photosensitizers for photo-immunotherapy, but also as an ideal drug carrier to achieve more efficient synergy. After loading with R837 (imiquimod, a toll-like receptor-7 agonist), MPSNs@R837 will elicit high-efficiency immunogenic cell death via PDT and PTT, and promote dendritic cell maturation after the PH-responsive release of R837, thereby, inducing tumor-specific immune responses. When combined with a programmed death ligand-1 checkpoint blockade, the photo-immunotherapy system markedly restrains primary tumors and metastatic tumors with negligible systemic toxicity. Therefore, the therapeutic strategy of integrating PTT, PDT and checkpoint blockade, shows great potential for suppressing cancer metastasis.Graphical

Extruded TOPAS hollow-core anti-resonant fiber optimized for THz guidance at 0.9THz.

A hollow-core anti-resonant fiber for the THz regime is proposed and demonstrated. The proposed fiber is the hexagonal core shape which is directly extruded using a conventional 3D printer. Experimental results show that by using cyclic olefin copolymer (COC), the proposed fiber design provides a low attenuation of ∼3 dB∕m at ∼ 0.86 THz and ∼15 dB∕m at ∼ 0.42 THz.

Thermal and morphological analysis of various 3D printed composite honeycomb cores

Fused deposition modeling (FDM) was employed to manufacture honeycomb core structures using polylactic acid (PLA) and short carbon fiber (CF) filled PLA composite filaments. For honeycomb structures, circular, square and hexagonal cores were manufactured to explore geometric effects on 3D printing quality. Various physical, thermal and compressive properties for their morphological features were holistically investigated. A comprehensive void analysis was also presented using optical microscopy, scanning electron microscopy (SEM) and X-ray computed tomography (XCT). Thermal analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) was also performed on honeycomb cores. It was manifested that material porosity was dependent on the structure, and had an inverse relationship with compressive properties. Hexagonal core structures especially possessed the lowest amount of material porosity with highest compressive strength relative to circular and square cores. It was also shown that XCT could be employed to estimate the microporosity within the structure, and further could be a useful tool to study the effect of filler addition in the matrix. In this study it was revealed via XCT that PLA/CF composite honeycomb cores yielded lower compressive properties compared to neat PLA structures owing to a large amount of microporosity generated in 3D printing process.

An experimental study on dynamic behaviour of a sandwich beam with 3D printed hexagonal honeycomb core filled with magnetorheological elastomer (MRE)

Sandwich beams with an aluminium face sheet and a magnetorheological elastomer (MRE) of varying proportions of elastomer and magnetic particles (weight to weight)% filled in a honeycomb core of Nylon and Resin8000 are manufactured and experimentally analysed in this study. To evaluate the dynamic properties of sandwich beams, manufactured structures subjected to sine sweep and classic shock tests and assessed both with and without magnetic field of varying intensities applied on the free end of the beam. The experimental results demonstrated good performance in vibration level attenuation, particularly in the structure’s primary vibration mode under consideration. The magnetic field applied was capable of lowering the first natural frequency of the proposed sandwich beam structures. Experiment results showed that an increase in an induced magnetic field shifted the natural frequencies, vibration amplitude, and damping ratio of sandwich panels with MRE honeycomb core.

Graphene-tethered 5-fluorouracil-loaded ZnO nanocomposites for pH-responsive enhanced efficacy in drug delivery on MCF-7 cells.

Graphene-tethered ZnO nanocomposites with rod shapes and oval-shaped 5-fluorouracil-loaded graphene-supported ZnO nanohybrids were synthesized using one pot wet chemical bottom up coprecipitation method. The presence of hexagonal nanophase of ZnO lattice with surface-tethered graphene sheets were confirmed using XRD pattern and supportive UV-Vis and FTIR spectrum. XRD data of these nanocomposites were matched with TEM images which proved the hexagonal ZnO core maintained even after surface tailoring with graphene and drug loading. These porous nanocomposites were loaded with anticancer drug 5-fluorouracil for enhancement in anticancer activity on breast cancer MCF-7 cells. The optical, morphological and phase physicochemical characterizations of the nanohybrids were performed using techniques as UV-Vis, FTIR, XRD spectrometry, and TEM microscopic analysis. The nanocomposites did not only exhibit biocompatibility but also pH responsive in vitro delivery applied for anticancer therapy on the basis of spectrometric MTT assay following sustained drug release with zero-order Peppas release kinetics. These nanocomposites exhibited higher anticancer activity on MCF-7 cells than free drug after in vitro MTT assay. On the basis of these demonstrations, these newer nanocomposites find future biomedical applications in pH-responsive drug delivery.

Ballistic impact response of reinforced honeycomb sandwich panels

Honeycomb sandwich panels are extensively adopted in a wide range of structures including aircraft, ships, automobiles, and infrastructure for being lightweight and occupying high out-of-plane compression and out-of-plane shear properties. They are evenly popular for their attractive energy absorption capability and resistance to ballistic impacts. Reinforcement of the hexagonal honeycomb panels is an efficient way to improve the impact resistance. However, a detailed study on the reinforcement types against ballistic impacts has not yet been reported. Therefore, the current research investigates the improvement of total energy absorption, ballistic limit velocity, and specific energy absorption (SEA) of three different reinforced hexagonal honeycombs, namely, triangular, circular, and hexagonal reinforcements against high-velocity blunt impacts. A parallel study is also carried out without any reinforcement and only thickening the cell wall of the non-reinforced hexagonal honeycomb panel. A numerical approach is adopted with commercial finite element code Ansys Explicit to analyze the virtual impact cases. The plate of the honeycomb panel is assumed as aluminum alloy Al-7075-T6, while the honeycomb core is made of Al-5083-H116. For both the alloy variants, Johnson-Cook flow stress parameters are utilized. For the projectile, a blunt cylindrical-shaped structural steel bullet is considered. It is found that, for the current investigations, triangular and circular reinforcements can significantly improve the overall ballistic performance of the sandwich panels with a penalty of weight increment. However, thickening the cell wall of the hexagonal core without any reinforcement exhibits the best ballistic performance.

Current Status and On-Going Development of VTT’s Kraken Core Physics Computational Framework

The Kraken computational framework is a new modular calculation system designed for coupled core physics calculations. The development started at VTT Technical Research Centre of Finland in 2017, with the aim to replace VTT’s outdated legacy codes used for the deterministic safety analyses of Finnish power reactors. In addition to conventional large PWRs and BWRs, Kraken is intended to be used for the modeling of SMRs and emerging non-LWR technologies. The main computational modules include the Serpent Monte Carlo neutron and photon transport code, the Ants nodal neutronics solver, the FINIX fuel behavior module and the Kharon thermal hydraulics code, all developed at VTT. The core physics solution can be further coupled to system-scale simulations. In addition to development, significant effort has been devoted to verification and validation of the implemented methodologies. The reduced-order Ants code has been successfully used for steady-state, transient and burnup simulations of PWRs with rectangular and hexagonal core geometry. The Ants–Kharon–FINIX code sequence is actively used for the core design tasks in VTT’s district heating reactor project. This paper is a general overview on the background, functional description, current status and future plans for the Kraken framework. Due to the short history of development, Kraken has not yet been comprehensively validated or applied to full-scale core physics calculations. A review of previous studies is instead provided to exemplify the practical use.

A new polyurethane-steel honeycomb composite pier anti-collision device: Concept and compressive behavior

A new type of pier anti-collision composite structure composed of honeycomb steel and polyurethane (PU) elastomer was proposed in this study. The impacts of the shape and filling materials of inner core cells on the failure mode, load–displacement cure, bearing capacity, structural stability, and energy absorption were studied by conducting uniaxial compression tests on device segments. Test results showed that the bearing capacity, structural stability, and energy absorption of honeycomb steel structure were significantly improved by PU elastomer filling. Besides, when compared with the square honeycomb structure and the regular hexagon honeycomb structure, the maximum values of average load, total energy absorption (TEA), and specific energy absorption (SEA), which were 69.6 kN, 1986.1 J, and 1300 J/kg, respectively, for the regular triangle honeycomb structure without PU filling, increased to 459.3%, 376.38%, and 212.5%, respectively, for the regular hexagonal core cell structure with PU filling, which was proved to be the most suitable core structure for pier anti-collision device.

Characteristics of Ultrasensitive Hexagonal-Cored Photonic Crystal Fiber for Hazardous Chemical Sensing

A highly sensitive non-complex cored photonic crystal fiber sensor for hazardous chemical sensing with water, ethanol, and benzene analytes has been proposed and is numerically analyzed using a full-vector finite element method. The proposed fiber consists of a hexagonal core hole and two cladding air hole rings, operating in the lower operating wavelength of 0.8 to 2.6 µm. It has been shown that the structure has high relative sensitivity of 94.47% for water, 96.32% for ethanol and 99.63% for benzene, and low confinement losses of 7.31 × 10−9 dB/m for water, 3.70 × 10−10 dB/m ethanol and 1.76 × 10−13 dB/m benzene. It also displays a high power fraction and almost flattened chromatic dispersion. The results demonstrate the applicability of the proposed fiber design for chemical sensing applications.

Design of 3D printed cores to improve radial compression behaviour of pultruded composite tubes

E-glass/vinylester composite crash structures manufactured by ultraviolet (UV) pultrusion process have shown high values of especific energy absorption (SEA). However, comparing the radial compression behaviour of the tubular structures with the axial crushing behaviour, it has been noticed that the stiffness and the strength of the structures to radial compression is too low. In order to improve the radial compression behaviour of the structures manufactured by UV pultrusion, different cores have been designed and manufactured by 3D printing using FDM (Fused Deposition Modeling) technology. On the one hand, an hexagonal core consit on a thin external skin made with ABS and filled with 3D printing support material has been analyzed. Otherwise, an hexagonal core designed following the honeycomb concept has been printed and tested. The composite structures with the cores have been tested in radial compression in quasi-static conditions and they have shown higher stiffness and strengh due to the 3D printed internal cores. The composite structure with the hexagonal ABS skin core and support material has improved the stiffness of the composite tubular structure 9 times while the strength has increased 5 times. In the case of the honecomb ABS core, the stiffness of the structure has increased from 1.15 kN/mm to 22 kN/mm (19 times more). Meanwhile, the strenght values using the ABS honeycomb core has been 17 times higher than the empty composite structure.

Investigation of specific energy absorption of natural fiber honeycomb sandwich structure composite as building construction material application

The usage of incorporating natural fibre in composite material has seen some potential to be used as a future building construction material due to its recyclability, lightweight and high-reliability feature. However, the issue of implementing natural fibre as building construction material in composites material concerns the structural integrity of the material. As the characteristics of the natural fibre honeycomb composite have been discovered more in terms of properties which ranges from its physical and chemical structural composition to the quasi-static impact collapse of the material, the absorption energy of the material in different cell geometry is unknown. Therefore, the purpose of this study involves the testing of the natural fibre honeycomb (NFH) composite made from cement fibre (face sheet) and corn starch (core) with regards to its crushing behaviour when subjected to flatwise compression load according to ASTM D-3410 standard to analyse the performance of energy absorption of NFH composite with different thicknesses of the hexagonal core and cell wall thickness to determine the Specific Energy Absorption of the material. The result obtained shows that the increasing thicknesses of the core and cell wall improves the ability of the composite to absorb more energy and the specific energy absorption is higher when both factors are increased.

Paper tube-guided blast response of sandwich panels with auxetic re-entrant and regular hexagonal honeycomb cores – An experimental study

Auxetic honeycomb structures have drawn increasing attention for impact/blast protection purposes owing to their superior indentation resistance and energy absorption capability. However, few comparative study on the blast performance among sandwich structures with different auxetic and non-auxetic cores has been performed to date. In this paper, the dynamic behaviors of metallic sandwich panels with auxetic re-entrant and regular hexagonal honeycomb cores (i.e. RHSPs and HHSPs) under the paper tube-guided explosions were investigated by a series of blast tests. The failure modes and underlying mechanisms of the target panels with different core relative densities under different impulse levels were classified and analyzed in detail. The panel blast resistance was evaluated by means of the back-face maximum permanent deflections, introducing the testing results of double arrowhead honeycomb sandwich panels (DAHSPs) in a separate paper. It indicates that the introduction of the paper tube achieved the concentration of shock energy, thus aggravating the panel central damage levels remarkably. For the RHSPs with NPR effect, the predominated failure modes of front faces transitioned essentially from the complete petal-like tearing to a local inner dome as the blast impulse decreased. The ones for the back faces ranged from partial tearing to pure global bending deformation, while the core failure modes tuned from central crushing and peripheral buckling to global compression deformation with central shrinkage and boundary adduction. Relative to the RHSPs, the equivalent HHSPs with a higher compressive strength were less insensitive to the blast intensity. Within the scope of present study, the DAHSPs could experience lower back face deflections than those of RHSPs regardless of core relative density. The auxetic honeycomb sandwich panels not always exhibited better over the non-auxetic HHSPs, which depended greatly on the blast impulse and core density level. This comparative research provides a useful reference for the auxetic sandwich honeycomb core design in protection applications.

Study and Analysis of Photonic Crystal Fiber for Broadband Laser Source Design

Photonic Crystal Fiber (PCF) has been a topic of extensive research in the field of nonlinear fiber optics. It is due to its combination of linear and nonlinear properties which ultimately results in the phenomenon having various types of applications. One of the phenomena is supercontinuum generation that has been extensively studied numerically and experimentally over the last few decades as it has important applications in the field of medical imaging and sensing. In this paper, we numerically analysed and studied PCF of hexagonal core with various parameters and propose our novel ‘Star in Hexagon’ design as a good candidate for the broadband supercontinuum generation and hence a broadband laser source. We numerically pumped a long 10 mm PCF of this kind at 3.1 um wavelength with a pulse having a power of 4000 W and a temporal width of 50 fs. A broadband supercontinuum ranging from 1.7 um to 18 um was obtained. The generated spectrum is quite well in the mid-infrared region. Hence it can be utilised for Mid – Infrared (MIR) applications.

All-composite honeycomb core sandwich structures: Master curves for stiffness-based design

Composite-walled hexagonal honeycomb core is considered for stiffness-based design. It is shown that the torsional and flexural stiffnesses of its all-composite sandwich may be 3- and 8-times higher, respectively, compared to structural foam core sandwich panel. This increase is attributed to an order of magnitude higher transverse shear resistance of composite-HC core. All-composite design can also outperform traditional aluminum core sandwich by about 25% and 60% increase in stiffness values under torsional and flexural loading. The results also reveal that stiffness of sandwich panel configurations of an arbitrarly fixed total structural weight can be mapped into unified “master design curves”. They suggest skin-to-core weight ratio for optimal flexural and torsional stiffnesses. The ratios herein are 1.3 and 2.6 respectively. The penalty of one on the other is about 8–10%. The ratio of 1.85 is the best compromise between the flexural and torsional stiffnesses reducing the trade-off to 2–3%.

Influence of geometric parameters on free vibration behavior of an aluminum honeycomb core sandwich beam using experimentally validated finite element models

The hexagonal honeycomb core sandwich panels used in the satellite structure are subjected to severe vibration during launch. Therefore, the amounts of natural frequencies of these panels are of great importance for design engineers. Three-dimensional finite element modeling of the core considering all geometric parameters (i.e., a high-fidelity model) to achieve accurate results is not cost-effective. The honeycomb core is traditionally equivalent to a homogenized continuum core (i.e., a low-fidelity model) using simple analytical relations with ignoring the adhesive layer at the double cell-walls and radius of inclined cell-wall curvature. In this study, analytical formulations are first presented for the prediction of the equivalent elastic properties of a hexagonal aluminum honeycomb with considering all geometric parameters including adhesive layer thickness, cell-wall thickness, inclined cell-wall length, radius of inclined cell-wall curvature at the intersection, internal cell-wall angle, and honeycomb height. Then, two aluminum honeycomb core sandwich beams with free-free boundary conditions are modeled and analyzed in Abaqus finite element software, one with 3D high-fidelity core and the other with 3D low-fidelity core. In order to validate the results of the equivalent model, the modal analysis test was performed and the experimental natural frequencies were compared. The obtained results show a good agreement between the 3D low-fidelity and high-fidelity finite element models and experimental results. In addition, the influence of the above-mentioned geometric parameters has been investigated on the natural frequencies of a sandwich beam. [Formula: see text]

GaAs/GaAsPBi core–shell nanowires grown by molecular beam epitaxy

We report on the growth, structural, and optical properties of GaAs/GaAsPBi core–shell nanowires (NWs) synthesized by molecular beam epitaxy (MBE). The structure presents advantageous optical properties, in particular, for near- and mid-infrared optical applications. Scanning electron microscopy shows that although the stems of GaAs/GaAsP and GaAs/GaAsBi core–shell NWs preserve the hexagonal prism shape, the GaAs/GaAsPBi core–shell NWs develop a quasi-three-fold orientational symmetry affected by the hexagonal prismatic core. Detailed structural analyses of a GaAs/GaAsPBi core–shell stem show that it crystallized with zincblende structure with a nominal shell composition of GaAs0.617P0.362Bi0.021. Photoluminescence of GaAs/GaAsPBi core–shell NWs shows the luminescent peak at 1.02 eV with high internal quantum efficiency at room temperature (IQERT ∼ 6%) superior to those of MBE-grown GaAs core NWs and GaAsPBi multiple quantum wells earlier reported. Energy-dispersive x-ray spectroscopy performed on the GaAs/GaAsPBi core–shell NWs yields an estimated bandgap different from the optically measured value. We attribute this discrepancy to the NW compositional fluctuations that also may explain the high IQERT.

Numerical investigation on the effect of different face sheet materials and core designs on the ballistic response of sandwich structures under low-velocity impact

In the present article, a detailed numerical deformation and failure analysis of sandwiched structures with different face sheet materials and core design has been carried out. Different face sheets materials ranging from aluminium alloys to composites such as carbon/epoxy and kevlar/epoxy fixed on different types of core were analyzed. Sandwiched structure with aluminium alloy face sheet showed minimum deformation of the impacting point, large impactor recoil and least strain energy absorption. Whereas carbon/epoxy face sheet showed large deformation of the impacting point for all the core designs. Employing the carbon/epoxy face sheet, the impactor recoiled only with square and hexagonal core design while the strain energy absorption was minimum for square and maximum for circular core designs. Kevlar/epoxy face sheet also showed large deformation of the impacting point for all the types of honeycomb core designs. The impactor recoiled very minimally for square core design and there was no recoil for the hexagonal and circular core. Kevlar/epoxy face sheet showed maximum displacement of the impacting point and strain energy absorption for the circular core. Thus, it can be said that sandwiched structure with a carbon/epoxy face sheet appeared to be the best choice in terms of energy absorption during the impact. The present study showed improvement in ballistic behaviour of sandwich structure with composite face sheet as compared to metallic face sheet in terms of energy absorption.

Strain-Mediated Magneto-Electric Effects in Coaxial Nanofibers of Y/W-Type Hexagonal Ferrites and Ferroelectrics

Nanofibers of Y- or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by electrospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed by electron and scanning probe microscopy. The values of magnetization of pure hexagonal ferrite fibers compared well with bulk ferrite values. The coaxial fibers showed good ferroelectric polarization, with a maximum value of 0.85 μC/cm2 and 2.44 μC/cm2 for fibers with BTO core–Co2W shell and PZT core–Ni2Y shell structures, respectively. The magnetization, however, was much smaller than that for bulk hexaferrites. Magneto-electric (ME) coupling strength was characterized by measuring the ME voltage coefficient (MEVC) for magnetic field-assembled films of coaxial fibers. Among the fibers with Y-type, films with Zn2Y showed a higher MEVC than films with Ni2Y, and fibers with Co2W had a higher MEVC than that of those with Zn2W. The highest MEVC of 20.3 mV/cm Oe was measured for Co2W–PZT fibers. A very large ME response was measured in all of the films, even in the absence of an external magnetic bias field. The fibers studied here have the potential for use in magnetic sensors and high-frequency device applications.

Full-Gradient Optimization of the Vibroacoustic Performance of (Non-)auxetic Sandwich Panels

This paper aims to optimize vibro-acoustic response of (non-) auxetic sandwich panels by use of topology optimization method. First, structural noise and vibration responses of the auxetic panel with the re-entrant hexagonal honeycomb core are studied. It is proved that the interactions between the structural vibrations and induced noise are more complex when expected for a low-frequency range, and the optimized noise reduction can be obtained by a proper combination of auxetic and non-auxetic properties within a single structure. Therefore, vibro-acoustic response of the sandwich panel with a re-entrant hexagonal honeycomb core by applying a full-gradient two-dimensional geometry optimization method is analyzed and optimized. It is shown that under various random loads, the sound power level can be reduced by about 20% at the cost of a slight increase (< 5%) of the total mass. Besides, the structural Eigen frequencies are shifted to lower values that are desirable for applications, e.g., in the aerospace industry. The obtained results ensure that the proposed optimization approach delivers extra noise reduction for auxetic sandwich panels as compared to the results available in the literature.

Bending response and energy absorption of sandwich beams with novel auxetic honeycomb core

In recent years, the enhanced auxetic honeycomb structure has attracted attention owing to its high strength and negative Poisson’s effect. The purpose of this study is to explore the bending response and energy absorption of the star-triangular honeycomb core (STH-C) and sandwich beam with an STH-C (STH-SW). Three-point bending tests and a series of numerical simulations are conducted to investigate the bending performance of the sandwich beams. The results indicate that STH-C exhibits only local bending deformation in the loading region, whereas the cells of the STH-SW undergo shrinkage deformation in the loading region, and the neighboring cells undergo tensile deformation. In addition, the deformation mode of the STH-SW is influenced by the compression position and structural parameters. Increasing the face sheet thickness and changing the thickness arrangements is beneficial to improving the load-bearing capacity of the sandwich beams, especially when tf/tb>1. Furthermore, the load-bearing capacity of the sandwich beams increase with the increase of the cell-wall angle and t/l, and increasing the t/l can change the cells from a global deformation to a local deformation mode. Subsequently, the complex proportional assessment method (COPRAS) is implemented to determine the influence weights of the structural parameters on the load-bearing capacity of the sandwich beams. The results demonstrate that the cell structure parameters have a more significant influence on the bending performance, especially the t/l. Finally, the bending performance of the STH-SW is compared with that of sandwich beams with different cores (star-shaped, re-entrant hexagonal and triangular corrugated structures). The results show that the energy absorption capacity of the STH-SW is 24.34% and 37.97% higher than that of sandwich beams with star-shaped and re-entrant hexagonal cores, respectively. Although the energy absorption capacity of the STH-SW is 10.25% less than that of multi-layer triangular corrugated core sandwich beam, there is no initial peak load for the STH-SW. This study is expected to provide some insights for further investigations on the bending performance optimization of sandwich beams with auxetic cores.