Resin Layer Research Articles

Формування розподілення конусних поверхонь у структурі оптичних дифузорів-гомогенізаторів

An analysis and research of formation of random and regular relief structures in optical diffusers-homogenizers are carried out. The features of the methods for manufacturing optical diffusers are considered too. The implementation of the formation of random relief structures in optical diffusers is proposed.The optical diffusers are widely used in beam guidance systems, remote control of complex industrial processes, lighting systems for various industrial applications and in other devices where there is a need to form a lighting beam with specified parameters. Unlike conventional frosted glass, the optical diffusers-homogenizers allow one to control the width of the light scattering indicator for more efficient use of the light beam in guidance systems.There are different methods of manufacturing optical diffusers, depending on the final purpose of use, including the conversion of amplitude holographic recording in relief-phase on halogen-silver photoemulsions, the formation of holographic structures on the surface of the photoemulsion in the form of relief indentation of the film layer on the layer of acrylic resin with the formation of a series of evenly distributed convex microspots on the layer of acrylic resin.The proposed methods have certain disadvantages with respect to their use in the guidance systems. The optical diffuser is made of soft polymeric material, which complicates its operation. Therefore, improving the methods of manufacturing optical diffusers remains an urgent task To solve this problem, a method of manufacturing an optical diffuser in the form of a relief microstructure is proposed, including the application of a hard-alloy conical indenter with an apex angle of 120–160° conical depressions on a metal substrate, which is later used as a stamp for thermal pressing of a relief microstructure in the form of conical protrusions on an optically transparent polymer material.To achieve high efficiency during homogenization and to avoid the appearance of a zero-order spot, the optical elements created by conical surfaces have to be structured with a fill factor of 100 %.The analysis and research of the formation of the distribution of conical surfaces in the structure of optical diffusers-homogenizers to obtain the most homogeneous structure of the light flux at the sites of the photodetector have been widely presented. Fig.: 7. Refs: 6 titles.

Development of environmentally friendly epoxy and composite adhesives and applications in single and mixed-modulus joints

Epoxy adhesives are common and useful materials in several fields, especially in making joints for the aerospace industry. Lately, there is a growing demand for this kind of adhesives to become more environmentally friendly. In this work, an environmentally friendly epoxy adhesive is developed using commercially available materials, exhibiting a 12% increase in green carbon content and 22% increase in shear strength. The commercial eco-friendly epoxy system is then reinforced with dry olive pit powder in order to produce an eco-friendly composite adhesive, giving a 20% shear modulus increase, for the 2.5% filler content, compared to the pure matrix. The behavior of these two materials is investigated, when these are used as adhesives in lap joints, and their main shear properties are determined. In order to manufacture adhesively bonded joints using a thick layer of liquid resin without any pre-curing step, therefore achieving improved properties, two casting-like designs of the overlap area are made and tested, one in a single-modulus configuration and a second one in a mixed-modulus mode. When an eco-friendly epoxy adhesive is applied on each edge of the mixed modulus mode instead of a fossil-based epoxy adhesive, a 30% increase in shear strength is observed. Finally, the Property Predictive Model, a modification and extension of the Modulus Predictive Model, is proposed, allowing the accurate prediction of several properties of virtually any series of particulate composite materials. When the model is applied to the aforementioned composites, it proves to be capable of accurately predicting their main shear properties.

Bio-Inspired Toughening of Composites in 3D-Printing.

Natural materials achieve exceptional mechanical properties by relying on hierarchically structuring their internal architecture. In several marine species, layers of stiff and hard inorganic material are separated by thin compliant organic layers, giving their skeleton both stiffness and toughness. This phenomenon is fundamentally based on the periodical variation of Young’s modulus within the structure. In this study, alteration of mechanical properties is achieved through a layer-wise build-up of two different materials. A hybrid 3D-printing device combining stereolithography and inkjet printing is used for the manufacturing process. Both components used in this system, the ink for jetting and the resin for structuring by stereolithography (SLA), are acrylate-based and photo-curable. Layers of resin and ink are solidified separately using two different light sources (λ1 = 375 nm, λ2 = 455 nm). Three composite sample groups (i.e., one hybrid material, two control groups) are built. Measurements reveal an increase in fracture toughness and elongation at break of 70% and 22%, respectively, for the hybrid material compared to the control groups. Moreover, the comparison of the two control groups shows that the effect is essentially dependent on different materials being well contained within separated layers. This bio-inspired building approach increases fracture toughness of an inherently brittle matrix material.

Large-Area Tunable Red/Green/Blue Tri-Stacked Quantum Dot Light-Emitting Diode Using Sandwich-Structured Transparent Silver Nanowires Electrodes.

Quantum dot light-emitting diodes (QLEDs), particularly those capable of emitting light with tunable colors, have attracted the attention of researchers for their variability in lighting and displays. So far, various color-tunable QLEDs have been developed using techniques of inkjet printing or white light combining with color filters (CFs), which however suffered from difficulties in mass production. Here, by inserting an insulating resin layer between two conductive silver nanowire (AgNW) layers, a unique AgNWs/resin/AgNWs (A/R/A) sandwich-structured electrode was developed, showing rather small sheet resistances at both sides and high transparency. The as-prepared A/R/A electrode is applicable for making a large-area transparent red QLED with an external quantum efficiency (EQE) of 11.42% and a transmittance of 72.5%. Furthermore, the A/R/A electrode can be used as intermediate connecting electrodes to stack three single-colored QLEDs, forming a novel structured R/G/B tri-stacked QLED, which enables emission not only of primary colors red, green, and blue independently with the maximum EQE of 8.22, 8.07, and 2.28%, respectively, but also arbitrary hybrid colors that cover a 107% National Television System Committee (NTSC) color triangle. Such large-area full-color-tunable tri-stacked QLED offers new perspectives for the next-generation solid-state scene lighting and full-color displays.

Modelling mechanism of Ca2+ removal from dicyandiamide using dynamic ion exchange method

AbstractBased on breakthrough theory and fractal porous medium theory (FPM), the paper investigates the modelling mechanism of Ca2+ removal in dicyandiamide by dynamic ion exchange. In this work, parameters within consideration included the flow rate of dicyandiamide crystallization mother liquor, the height‐diameter ratio of the resin layer, and the temperature on Ca2+ exchange. It was found that the removal efficiency of Ca2+ reached 97.32%. Meanwhile, the through function of the process was obtained, and the behaviour of the dynamic process was modelled and simulated. In addition, using FPM theory, the calculation equation of the spectral dimension of the fractal surface of the resin in the ion exchange process was observed as linear and a mathematical model was established. This paper analyses the dynamics equation of the ideal surface and the fractal surface. According to the analytic results, it was linear relation on the ideal surface and power function on the fractal surface.

Resin-coated beads in Iberian Late Prehistory (3rd–2nd millennia BCE)

ABSTRACT A group of beads from the artificial cave of La Molina (Lora de Estepa, Sevilla) and Cova del Gegant (Sitges, Barcelona) were made from biogenic raw material and intentionally covered by a layer of resin. This is the first time this type of treatment has been documented on elements of adornment in the Late Prehistory of the Iberian Peninsula. The composition and nature of the coatings are analyzed and the symbolic role of such alterations and imitations of prehistoric adornments is discussed.

An experimental study on damaged cementitious mortars repaired by glass/epoxy composite materials

Abstract This paper presents an experimental investigation on the post-repair flexural response of mortars with and without damage. In order to improve the mechanical properties of the damaged mortars, which were subjected to different loads ranging between 40 % and 90 %, the mortars specimens were reinforced and repaired using two different composite materials, the first with only epoxy resin, while the second consisted of a mixture of epoxy resin and glass fiber. The results show a significant improvement in the stiffness damaged. Therefore, the reinforced specimens by a layer of resin on the lower side surface increased the bending strength by 58 %, when compared to those control samples. The reinforcement using composite resin-fiber of glass exhibited considerable increases in the safety of constructions. The SEM images of damaged samples with and without repair, revealed the impact of reinforced glass fibers-mortar on the matrix-mortar by improving theirs mechanical performances.

Optimal Layer Thickness during the Design of Carbon Fiber Composite under Bending Loading

Carbon fiber resin composite materials are widely used in manufacturing and industrial production due to their many performances better than that of traditional materials. However, how to use the limited carbon fiber resin composite material to design the product with the excellent bearing capacity and relatively low processing cost still needs to be explored. The layer thickness is an important parameter during the design of carbon fiber composite. Large layer thickness between carbon fiber layer and resin layer could lead to poor mechanical properties. Small layer thickness could improve the bearing capacity but accompany with the high cost of production. Optimal layer thickness can balance the mechanical properties and production costs. Here, Abaqus software was employed to establish the finite element models with the same size but different number of layers, by dividing the mesh and finding the ultimate bearing capacity of each model, the relationship between the model layer and the ultimate loading force was obtained. Based on the calculated results, the optimal design scheme of carbon fiber resin composite materials was proposed.

Baseline-free defect evaluation of complex-microstructure composites using frequency-dependent ultrasound reflections

In this study, baseline-free defect characterization for both flat and ply-drop composites were proposed using frequency dependence of ultrasound reflections. This frequency dependence of ultrasound interaction with delamination and resin layers in composites were investigated through CIVA® simulation and experimental investigation. To extract quantitative data of frequency dependence of ultrasonic reflections in composites with a single test, synchrosqueezed wavelet transform was adopted to decompose the acquired wide-band raw signals into narrow-band frequencies. Quantitative analysis concluded that dependence of ultrasound reflections from defects on frequency in composites are affected by wavelength-to-defect ratio, polymer viscoelasticity, frequency-dependent inter-ply reflections and waviness-induced scattering. Considering these factors, our study found that volumetric defect reflections have a unique frequency dependence. This allows volumetric defect identification and characterization in ultrasonic B-scans to be achieved without comparison to a baseline reference. The proposed method shows a promising solution for non-destructive evaluation of multi-layer composites with diverse microstructures.

Determining the setting of root canal sealers using an in vivo animal experimental model.

To present and explore the potential of an animal-based experimental model developed to determine the set of root canal sealers in vivo. The setting of AH Plus, BioC Sealer, TotalFill BC Sealer, and Sealapex was determined using either ISO 6876 or the novel in vivo method proposed in this study. The in vitro setting time of the sealers tested was determined in accordance with ISO 6876:2012. In determining the in vivo set, 24 adult Wistar rats were followed up for two evaluation periods: 1 and 4 weeks. Their upper-right incisor was extracted, and its pulp tissue was removed. The root canal was then filled from retrograde with one of the 4 sealers, and the tooth was re-implanted and fixed with a layer of a flowable composite resin. After 1 or 4 weeks of the surgical procedures, the animals were euthanized, and their incisors were extracted. Two-mm-thick slices of the middle third of the tooth root were obtained and assessed with a Gillmore device, to determine whether or not the sealer had set. The following in vitro results were obtained by using ISO 6876 methodology: AH Plus set after a mean time of 423 ± 20 min and 476 ± 35 min, in metal and plaster molds, respectively. BioC Sealer set after 7 days (in dental plaster molds), whereas TotalFill BC Sealer and Sealapex did not set even after 25 days in both tested conditions (metal or dental plaster molds). Using the novel in vivo methodology, AH Plus, BioC Sealer, and TotalFill BC Sealer set after both 7 and 30 days. In contrast, Sealapex did not set at either time point. AH Plus and BioC Sealer set under both in vitro and in vivo test conditions. TotalFill BC Sealer did not set under in vitro conditions but did after 1 week under in vivo conditions. Sealapex did not set under either in vitro or in vivo conditions. The influence of the testing conditions on the setting results is a clear indication that new in vivo experimental models should be useful in future studies on Bioceramics root canal sealers.

Reduction of long-term irreversible membrane fouling: A comparison of integrated and separated processes of MIEX and UF

In this study, the reductions of long-term irreversible membrane fouling in integrated and separated MIEX-UF processes were explored over a prolonged experimental period. The mechanism leading to the significant difference in membrane fouling behaviors of the two processes was systematically analyzed. The results show that the chemical cleaning frequency and the rate of chemically irreversible membrane fouling formation were decreased by 50% and 49%, respectively, in the integrated process compared to the separated process. Further analysis suggested that MIEX adsorption was unrelated to the different membrane fouling behaviors between the two processes. The effect of the resin layer on filtration and backwashing was the dominate mechanism leading to the more excellent anti-fouling performance of the integrated process. The stronger adhesion force of pollutants-MIEX enable the mixed cake layer formed in the integrated process to maintain good water permeability and easy to be removed by backwashing. The adhesion force of pollutants-MIEX was significantly affected by the saturation level of resin particles and less affected by resin regeneration. During the early period of long-term filtration experiment and the initial stage after every resin replacement, the low saturation degree of resin particles guaranteed the improved effect of the resin layer always existed.

Effects of Surface Energy Reducing Agents on Adhesion Force in Liquid Bridge Microstereolithography

Projection microstereolithography (MSL) is a layer-by-layer manufacturing process used to fabricate three-dimensional (3D) microstructures. In this process, each layer of a photoreactive liquid resin is crosslinked by modulated ultraviolet (UV) light through a digital micromirror device (DMD). Despite the capabilities of MSL, there are some drawbacks such as incompatibility with highly viscous materials, long manufacturing time, large material consumption, and oxygen inhibition. To address these issues, liquid bridge microstereolithography (LBMSL) has been proposed as a vat-free process, which involves using a liquid resin supported by a capillary bridge between two substrates. One of the most important manufacturing steps in the LBMSL process is to detach the cured layers from the upper transparent substrate, without causing any damage to the structure during the 3D printing process. This paper has investigated the use of a small molecule additive, a surface energy reducing agent (SERA) that tends to migrate toward the transparent substrate and reduces adhesion at this interface. This has been proven through a series of adhesion force measurements and material characterization methods. The migration of SERA molecules has been studied using contact angle measurements and x-ray photoelectron spectroscopy (XPS). In addition, tensile measurements reveal that there are no detrimental effects on the mechanical properties of the resin due to adding SERA in the formulation. Multiple 3D microstructures have been fabricated to illustrate the advantage of adding SERA to reduce the adhesion of the resin to the transparent substrate in LBMSL.

Thermomechanical Modeling of a Sleeve Rehabilitation System for Pressure Pipes

Abstract The thermomechanical modeling of a sleeve rehabilitation system for pressure pipes is studied including temperature effect on system behavior. The rehabilitation system consists of a multicylinder axisymmetric layer system, with an intermediate layer of epoxy resins and two outer steel covers that are longitudinally welded forming a sleeve. The analysis is conducted over several stages; initially, the incidence of temperature on the rigidity of three types of resins currently available on the market is experimentally evaluated. Then, nonlinear relationships between rigidity and temperature are established from the evaluation of the resins, which are typical of an inhomogeneous material. The resins exhibit a significant loss of rigidity with temperature, generating a risk of delamination that could drastically reduce the effectiveness of the rehabilitation system in the event of possible temperature rises. An analytical model was developed to calculate contact pressures between the resin layer and the external sleeve, internal pipeline displacements, stresses, and deformations. Finally, contour plots were developed for different temperature, pressure levels, and pipe thickness as a graphics tool to predict pipeline failure due to plastic deformation or rupture.

Ultrasonic-assisted preparation-forming-curing process for ultra-thin micro-fiber metal laminates: Deformation characteristics

At present, Fiber metal laminates (FMLs) are mostly used in the aeronautical field to manufacture large-size components, such as skins of fuselage or wing. However, the utilization of FMLs in microsystems and micro-electro-mechanical systems has not been explored yet. Therefore, miniaturization of conventional FMLs and integration of micro-sheet preparation and complex-shaped components forming are of utmost significance from a practical viewpoint. Herein, an integrated ultrasonic-assisted preparation-forming-curing method is proposed to manufacture ultra-thin micro-Ti/Cf/PPS hybrid laminates (TA1/Carbon fiber/PPS) components in this paper. The influence of ultrasonic vibrations on the performance of as-prepared micro-laminates is systematically studied, including the immersion distribution of PPS resin in Cf layer, interfacial bonding properties of Cf/PPS and Ti/PPS interfaces and micro-deformation mechanism of metallic layer. Furthermore, the hot bulging test is carried out by rapid transfer of the micro-laminates at melting temperature (280 °C) of the resin layer using a micro-arrayed spherical-cap die to assess the formability. A combination of electron backscatter diffraction (EBSD) analysis, metallographic observations and image precision measurement revealed the unique deformation characteristics and thickness evolution of complex-shaped micro-Ti/Cf/PPS laminates. Overall, a high deformation level is achieved during the bulging process. The current study provides an enhanced understanding of ultrasonic-assisted micro-forming-curing process.

Density compensated diodes for small field dosimetry: comprehensive testing and implications for design

Purpose. In small megavoltage photon fields, the accuracies of an unmodified PTW 60017-type diode dosimeter and six diodes modified by adding airgaps of thickness 0.6–1.6 mm and diameter 3.6 mm have been comprehensively characterized experimentally and computationally. The optimally thick airgap for density compensation was determined, and detectors were micro-CT imaged to investigate differences between experimentally measured radiation responses and those predicted computationally. Methods. Detectors were tested on- and off-axis, at 5 and 15 cm depths in 6 and 15 MV fields ≥ 0.5 × 0.5 cm2. Computational studies were carried out using the EGSnrc/BEAMnrc Monte Carlo radiation transport code. Experimentally, radiation was delivered using a Varian TrueBeam linac and doses absorbed by water were measured using Gafchromic EBT3 film and ionization chambers, and compared with diode readings. Detector response was characterized via the formalism, choosing a 4 × 4 cm2 reference field. Results. For the unmodified 60017 diode, the maximum error in small field doses obtained from diode readings uncorrected by factors was determined as 11.9% computationally at +0.25 mm off-axis and 5 cm depth in a 15 MV 0.5 × 0.5 cm2 field, and 11.7% experimentally at −0.30 mm off-axis and 5 cm depth in the same field. A detector modified to include a 1.6 mm thick airgap performed best, with maximum computationally and experimentally determined errors of 2.2% and 4.1%. The 1.6 mm airgap deepened the modified dosimeter’s effective point of measurement by 0.5 mm. For some detectors significant differences existed between responses in small fields determined computationally and experimentally, micro-CT imaging indicating that these differences were due to within-tolerance variations in the thickness of an epoxy resin layer. Conclusions. The dosimetric performance of a 60017 diode detector was comprehensively improved throughout 6 and 15 MV small photon fields via density compensation. For this approach to work well with good detector-to-detector reproducibility, tolerances on dense component dimensions should be reduced to limit associated variations of response in small fields, or these components should be modified to have more water-like densities.

Electrochemical, mechanical and adhesive properties of surface modified NiO-epoxy nanocomposite coatings on mild steel

The effect of surface modification of NiO (nickel oxide) nanoparticle by (3-Mercaptopropyl) triethoxysilane (MPTES) in the epoxy-NiO nanocomposite coatings on mild steel was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques in seawater. MPTES was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of NiO nanoparticle in the epoxy coating enhances the charge transfer resistance (Rct) as well as the film resistance (Rf). The observation of iron dissolution and oxygen consumption was carried out using an appropriate potential at the SECM tip in the NiO modified nanocomposite coated steel. The pure epoxy and epoxy-NiO nanocomposite coated samples were used to study the mechanical, adhesion, and anticorrosion properties. The analysis by field emission-scanning electron microscopy/energy dispersive X-ray analysis (FE-SEM/EDX) displayed the enriched Ni was detected in the nanocomposite coating of steel. The presence of the nano level corrosion product containing Ni was confirmed by focused ion beam-transmission electron microscopy (FIB-TEM) analysis. The high corrosion protection properties of epoxy nanocomposite coatings were due to the formation of complex nanoscale layer and chemical interactions of epoxy resin with surface modified nanoparticle in nanocomposites.

Modified phenolic resin with aluminium and rectorite: Structure, characterization, and performance

AbstractPhenolic resin is an important binder for refractory ceramics. Herein, aluminum and organic rectorite were employed to improve the antioxidant activity of phenolic resin. X‐ray diffraction revealed that the silicate layers of phenolic resin exfoliated rectorite were uniformly dispersed in the modified phenolic resin (MPF) matrix. Moreover, TEM revealed that the peeled silicate nanoparticles from rectorite were well distributed without clustering. The structure of the MPF resin was also analyzed by infrared spectroscopy and nuclear magnetic resonance. The results showed that the strength of the ether bridge of MPF resin with aluminum and rectorite considerably decreased than that of pure phenolic resin. The MPF resin was anhydrous and had AlO bonds to link the benzene rings. Pyrolytic carbon experiments revealed that the decomposition temperature of the MPF resin was 759.2°C, which indicated that it had a better oxidation resistance and bonding strength than those of pure phenolic resin. The incorporation of aluminum and rectorite improved thermal performance of the phenolic resin, and enhanced mechanical performance of the MgOC refractory.

Performance of Short Fiber Interlayered Reinforcement Thermoplastic Resin in Additive Manufacturing.

To further improve the mechanical properties of thermoplastic resin in additive manufacturing (AM), this paper presents a novel method to directly and quantitatively place the short fibers (SFs) between two printing process of resin layers. The printed composite parts with SFs between the layers was reinforced. The effects of single-layer fiber content, multi-layer fiber content and the length of fibers on the mechanical properties of printed specimens were studied. The distribution of fibers and quality of interlayer bonding were assessed using mechanical property testing and microstructure examination. The results showed that the tensile strength of the single-layered specimen with 0.5 wt% interlayered SFs increased by 18.82%. However, when the content of SFs continued to increase, the mechanical properties declined because of the increasing interlayered gap and the poor bonding quality. In addition, when the interlayered SFs length was 0.5–1 mm, the best reinforcement was obtained. To improve the interfacial bonding quality between the fiber and the resin, post-treatment and laser-assisted preheating printing was used. This method is effective for the enhancement of the interfacial bonding to obtain better mechanical properties. The research proves that adding SFs by placement can reduce the wear and breakage of the fibers compared to the conventional forming process. Therefore, the precise control of the length and content of SFs was realized in the specimen. In summary, SFs placement combined with post-treatment and laser-assisted preheating is a new method in AM to improve the performance of thermoplastic resin.

Comparison of the dielectric properties of functionally graded material dielectrics and layered dielectrics used for electric stress control

Layered dielectric materials are currently in use for electric field stress control, but are limited by charge accumulation at the dielectric–dielectric interfaces. The current work uses micrometric particles to modify the effective permittivity of epoxy resin samples. Two broad kinds of samples are considered: discrete layered material (DLM) samples and functionally graded material (FGM) samples. DLM samples are obtained by bonding layers of epoxy resin with different filler loadings such that abrupt variation in permittivity might occur along the sample thickness. FGM specimens are prepared by hot pressing a comparatively large number of very thin layers of micro-filled epoxy resin with very small differences in permittivity one over the other, thus creating a gradual spatial permittivity gradation. Dielectric properties of FGM and DLM specimens are compared in this study. Space charge accumulation is studied using the pulsed electroacoustic method; the accumulated charge density is seen to be lower in FGM. The uniformity of electric field distribution under applied electric stress is computed, and the field utilisation factor in FGM is seen to have a higher value. Also, the dissipation factor is lower and the short-term breakdown strength is higher in FGM than in DLM samples, providing reason to prefer FGM for insulation to control electric stress.

Fabrication and analysis of radiation dose for elastic lead polyester composites as a glass coating

Radiation affecting the human body can cause harm to workers from the lightest to the most fatal. As a result of these interactions, cells can undergo structural changes. Therefore a radiation shield is needed for radiation protection purposes. In this research, a polyester composite sample was made with a variation of lead doping concentration and illumination strength test using a flux meter to determine the permeability of the sample to light, as well as an X-ray radiation absorption test of the sample as desired by the lead polyester being able to be an alternative from the constituent materials of lead glass as a radiation shield that has the advantage of a high level of elasticity so as to minimize the risk of damage (break). Obtained the best mixture composition of 30% Lead Acetate and 70% Lead Polyester, with a radiation exposure test of 35 µSv the results of the radiation absorbing dose on the thickness of the 15mm lead resin layer and Transparency test with an inhibitory value of light of 394 Lux from an initial light source of 700 lux and the rest of the light that is able to penetrate a sample of 306 Lux