Polymer Sheets Research Articles

3D Printing and Easy Removal of Transparent Thin Polymeric Sheets and their Application in Solar Cells Encapsulation

In this work, article number 2300183 by Nazek El-Atab and co-worker, a cost-effective method for 3D printing of highly transparent and thin sheets using a digital light processing technique and a modified build plate is proposed. The application of this approach in 3D printing an encapsulation polymeric layer for solar cells with the ability to block UV light for thermal management is demonstrated.

P35: Characterization and Comparison of Thermoplastic Material Performance Using Pressure-Volume Relationships

Purpose: Characterizing mechanical performance of finished materials can be challenging due to geometric constraints and the effects of downstream processing on raw material behavior. The following describes a more sensitive test method to accurately characterize the performance of a thin polymeric sheet material. Methods: Two different polymers, Thermoplastic Polyurethane, TPU, and Thermoplastic Elastomer, TPE, were selected for characterization. Each was molded and assembled into a manifold. Both polymers were under a constant pressure load over time, as a control and measurement technique. Fluid was injected incrementally into the assembly and the resulting injectate volume was measured by mass difference up to a limit volume to understand material behavior post processing. Results: The plotted pressure-volume relationships were distinct between TPU and TPE at two time intervals, as shown in Figure 1. A reduced pressure response to the same volume at test repetition demonstrated that both materials showed permanent set over time. Volume offset between sample runs illustrated reduced mechanical performance over time due to material creep. Conclusion: The pressure-volume testing method successfully characterized performance of the materials over time to discriminate the material set properties between two thin polymeric sheet material, which could not be detected for a finished component using traditional tensile test methods. This repeated method can be used during material selection in various applications for materials with a manufactured finished component, especially for the medical device industry where polymers are carefully chosen and designed for a specific function.

Changes in fracture energy at FRP-concrete interfaces following indoor and outdoor exposure with sustained loading

Small-scale plain concrete precracked beams strengthened with carbon and glass fiber reinforced polymer (FRP) sheets were tested in 3-point flexure to evaluate changes in the FRP-concrete Mode II interfacial fracture energy following sustained loading for 6 and 13 years in indoor and outdoor environments. Mode II fracture energy of the interfacial region, GF, was calculated using strain profiles along the length of the FRP sheet, which were measured using digital image correlation and photoelastic techniques. In the post-conditioned experiments, larger GF values were measured as the debonded zone progressed from the sustained shear stress transfer region to the unstressed portion of the interfacial region far from the notch, particularly in beams with outdoor conditioning. In the interfacial region near the notch, the carbon FRP beams showed no reduction in GF in the indoor environment but reduction in the outdoor environment, while glass FRP showed reductions in both environments. In outdoor beams with glass FRP sheets, GF was not additionally degraded when the FRP was exposed to direct sunlight, in comparison to beams with the FRP exposed to indirect sunlight.

PRODUCTION AND OPTIMIZATION OF BIOPLASTIC FROM BACILLUS ISOLATED FROM ENVIRONMENTAL SAMPLE

Biopolymers represent a major alternative to petroleum-derived plastics, with poly-3-hydroxybutyrate (PHB) being the most common. To reduce the cost of production and expand the use of such biopolymers, our research focused on identifying microorganisms with effective PHB-producing capabilities. Through standard microbiological procedures, we isolated six different samples and used Sudan Black B colony staining to determine their PHB-producing capabilities. The Crotonic acid method revealed a 90.1% yield of PHB in the sample. Biochemical, morphological, and molecular analyses - including 16S rRNA gene sequencing - confirmed the bacterium as Bacillus cereus. FTIR analysis was also used to confirm the polymer as PHB. Furthermore, the ability of Bacillus cereus to use various carbon sources, coupled with gentamycin encapsulated in PHB polymer sheets to effectively demonstrate its antimicrobial properties, and a cell viability analysis to show its biocompatibility, highlight this microorganism as an effective candidate for large-scale industrial production of bacterial polyhydroxybutyrate.

High temperature behaviour of basalt fibre-steel tube reinforced concrete columns with recycled aggregates under monotonous and fatigue loading

Experimental and numerical investigations were carried out to evaluate the effects of incorporating recycled coarse aggregates (RCA) on the mechanical behaviour of inner steel-tube reinforced concrete columns exposed to high temperature. The specimens were reinforced with basalt fibres (BF) and strengthened by carbon fibre reinforced polymer (CFRP) sheets, which were subjected to mechanical loading in monotonous and cyclic arrangements. Test results show that at room temperature (RT), incorporation of the chopped BF has reduced both the tensile strength and flexural strength of concrete specimens prepared with recycled aggregate concrete (RAC) but not their static elastic modulus. On the other hand, the BF has improved crack resistance of the steel tube reinforced RAC (STRC) column specimens. Also, the reduction in mass and dynamic elastic modulus of BF reinforced STRC specimens are lower than those of STRC at a given RCA replacement ratio and exposure temperature. Furthermore, improvements in mechanical performance under monotonous and fatigue loading was observed for STRC columns reinforced with BF and externally bonded CFRP sheets with high-temperature exposure (HTE). Therefore, it is possible that BF reinforced STRC columns could be used to reduce risk of brittle structural collapse when exposed to fire or elevated temperature.

Projectile impact-induced spalling damage on carbon fiber reinforced polymer strengthened RC plates

As the most widely used material in protective structures, a better understanding of the resistance of reinforced concrete (RC) to high-speed projectile striking is needed. It has been accepted that concrete material possesses limited impact resistance in virtue of its poor energy absorption capacity. To improve the performance of RC structures under impulsive loading, affixing externally-bonded Fiber Reinforced Polymer (FRP) sheets on structural elements is a practical method. Due to the emphasis of most existing literature on the penetration behavior of projectiles, the studies of impact-induced spalling damage on normal and FRP strengthened RC plates are not sufficient and in-depth. In this paper, the local response of un-strengthened and FRP strengthened RC plates under projectile impact is systematically investigated with experimental approaches. In consideration of the complexity of transient behavior as well as multiply parameters involved, empirical approaches based on dimensionless analysis are proposed to predict the diameter and depth of spalling craters on normal RC plates and strengthened ones with frontal CFRP layers, which fill current research gap and are potential tools for damage assessment and repair. The validity of the proposed approaches is verified by test results from the present and published studies.

A Space‐Confined Polymerization Templated by Ice Enables Large‐Scale Synthesis of Two‐Dimensional Polymer Sheets

AbstractDespite significant progress in the preparation and characterization of two‐dimensional (2D) materials, the synthesis of 2D organic materials remains challenging. Here, we report a novel space‐confined polymerization method that enables the large‐scale synthesis of 2D sheets of a functional conjugated polymer, namely, poly(3,4‐ethylenedioxythiophene) (PEDOT). A key step in this method is the confinement of monomer to the boundaries of ice crystals using micelles. This spatial confinement directs the polymerization to form 2D PEDOT sheets with high crystallinity and controlled morphology. Supercapacitors prepared from the 2D PEDOT sheets exhibit outstanding performance metrics. In aqueous electrolyte, a high areal specific capacitance of 898 mF cm−2 at 0.2 mA cm−2 along with an excellent rate capability is achieved (e.g., capacitance retention of 67.6 % at a 50‐fold higher current). Moreover, the 2D PEDOT‐based supercapacitors exhibit outstanding cycling stability (capacitance retention of 98.5 % after 30,000 cycles). Device performance is further improved when an organic electrolyte is used.

A Space-Confined Polymerization Templated by Ice Enables Large-Scale Synthesis of Two-Dimensional Polymer Sheets.

Despite significant progress in the preparation and characterization of many two-dimensional (2D) materials, the synthesis of 2D organic materials remains challenging. Here, we report a novel space-confined polymerization method that enables the large-scale synthesis of 2D sheets of a functional conjugated polymer, namely, poly(3,4-ethylenedioxythiophene) (PEDOT). A key step in this method is the confinement of monomer to the boundaries of ice crystals using micelles. This spatial confinement directs the polymerization to form 2D PEDOT sheets with high crystallinity and controlled morphology. Supercapacitors prepared from the 2D PEDOT sheets exhibit outstanding performance metrics. In aqueous electrolyte, a high areal specific capacitance of 898 mF cm-2 at 0.2 mA cm-2 along with an excellent rate capability is achieved (e.g., capacitance retention of 67.6% at a 50-fold higher current). Moreover, the 2D PEDOT-based supercapacitors exhibit outstanding cycling stability (capacitance retention of 98.5% after 30,000 cycles). Device performance is further improved when an organic electrolyte is used.

Behavior of large-scale columns strengthened with basalt fiber-reinforced polymers sheets or bars and hybrid FRPs

Basalt fiber-reinforced polymers (BFRP) have recently become a widely used material for increasing the ultimate load capacity of reinforced concrete (RC) columns and improving their behavior throughout their entire life. So, an experimental program consisting of 19 large-scale RC columns of low strength has been prepared to examine the behavior of strengthened RC columns at all stages of loading. In this program, the columns were divided into two groups. The main parameters include the strengthening materials (BFRP wrap, BFRP bars, and carbon fiber reinforced polymers (CFRP) wrap), the strengthening techniques (fully or partially wrapping, the number and direction of layers), the cross-sectional shapes (square, rectangular, and circular), and the loading types (eccentric and concentric). The confinement of BFRP wraps significantly improved the service load and the ultimate failure load. The hybrid systems achieved an adequate level of confinement of the strengthened columns, increased the maximum load by 43.61 %, and absorbed energy by 477.2 % compared to the control column. BFRP bars used as a near-surface mounted material improved the behavior of the columns by up to 60 % and 411 % in maximum load and absorbed energy, respectively. The ACI and ECP codes predicted good estimates for the stress of columns strengthened with a single layer but underestimated for columns strengthened with a single layer and BFRP bars. Based upon the existing test data, BFRP-RC is recommended. Furthermore, this research can support using BFRPs as strengthening materials.

3D Printing and Easy Removal of Transparent Thin Polymeric Sheets and their Application in Solar Cells Encapsulation

3D printing of thin transparent sheets is challenging because transparency is compromised due to surface defects. Herein, the 3D printing of thin, transparent, and smooth polymeric surfaces is demonstrated with easy removal and potential application in solar cell encapsulation. Thin disk‐shaped objects are printed using a vat‐photopolymerization‐based 3D‐printing technique, and their transparency is measured. The disks are printed directly onto the build plate in three different orientations, whereas a modified build plate is used for each sample. The sample printed on the modified build plate exhibits the highest transparency (≈95%) and is the easiest to remove from the plate. Thin and transparent sheets are prepared with embedded TiO2 nanoparticles using this approach. TiO2 addition blocks the ultraviolet‐light wavelengths of 200–400 nm, which can reduce phonon generation in silicon solar cells and, thus, lower the panel surface temperature. The results demonstrate an 8 °C reduction in temperature, which can enhance the efficiency of silicon photovoltaics. The proposed method demonstrates the capability of 3D printing of transparent, smooth surfaces with easy removal of thin objects for various applications.

Structural strengthening of a constructed timber bridge: Field application and numerical modeling

This paper presents the behavior of a timber bridge strengthened with lag bolts, carbon fiber reinforced polymer (CFRP) sheets, and hollow structural sections (HSS). The 83-old bridge is composed of three spans, supported by 14 Douglas Fir girders, and is tested employing truck loadings of 120 kN and 267 kN. Three-dimensional finite element models are formulated to study the flexural response of the bridge with and without the retrofit options. The magnitude of the truck load dominates the degree of dispersion in girder deflections and alters the shape of probability density functions, which are associated with behavioral uncertainty. The effectiveness of strengthening is apparent in terms of reducing the exceedance probability of deflection limits and increasing reliability indices above the design threshold of β = 3.5, stipulated in bridge specifications. Among the three methods, the stiffening efficiency of the HSS option is higher at the system level; however, the use of CFRP is most efficient at the member level. Live load distribution factors are examined and implementable recommendations are provided for practice. Parametric investigations clarify the efficacy of variable HSS sizes and the ramifications of a permit truck weighing 445 kN.

Polarization response characteristics of 6061Al and PMMA sheets under impact load

The material will induce shock polarization under the action of shock wave. Aluminum alloys (such as 6061Al) are used as the main material for spacecraft skins, panels and frames. The impact polarization effect generated during the cratering deformation (compression and shearing) of space debris will induce the surface discharge of the orbiting satellite. Polymethyl methacrylate (PMMA) materials are often used in combination with electronic devices of weapon equipment. Under high overload, PMMA will produce shock polarization effect, electromagnetic interference on electronic devices, and even trigger by mistake. Therefore, it is of great significance to reveal the impact polarization characteristics of different types of materials (metal, polymer) for improving the bulletproof protection ability of in-orbit satellites, protective armor and electronic devices. In this paper, the 6061Al and PMMA thin plates were taken as the research object, and the universal testing machine combined with LCR was used to measure the capacitance and resistance of 6061Al and PMMA under different given loads by combining theoretical analysis, experiment and simulation. At the same time, the first stage light gas gun is used to study the local impact induced electro-mechanical response of metal and polymer sheet materials. On this basis, the AUTODYN-ABAQUS/Explicit-COMSOL co-simulation under corresponding experimental conditions was carried out to obtain the distribution rules of temperature and strain gradient. Based on the theory of flexoelectric effect, the impact polarization response characteristics of 6061Al and PMMA materials were clarified, respectively. The results show that the impulse polarization voltage of 6061Al thin plate increases first and then gradually decreases with time. The impulse polarization voltage is proportional to the thickness. The polarization voltage of single-electrode PMMA thin plate is parabola; the polarization voltage of PMMA thin plate with two electrodes increases first and then gradually decreases. The absolute value of the strain gradient of the 6061Al thin plate increases first and then becomes stable, while the strain gradient of the PMMA thin plate increases first and then decreases.

Detection of Composites and Sandwich Structures for Aeronautic Application

"An overview of sandwich structures in aviation applications is provided in this article. It emphasizes the complexity of designing these structures and addresses the main issues that designers face while working with them. Beginning with early instances from the 1930s and focusing on their significant development during World War II, the article examines the evolution of sandwich structures. It explores their wide range of uses in both civil and military spheres. The article also investigates the impact of polymer materials and sheet technology on the mechanical characteristics of composite sandwich constructions. The essay covers three different types of sandwich structures that were created using manual lay-up, press technique, and autoclave application manufacturing processes. These sandwich specimens underwent impact load tests to determine their failure properties. The structural analysis focused on sandwich panels produced in a similar manner, with an adhesive layer between the cores. The goal of the study was to generate research findings about the effects of stress during sandwich panel fabrication on several mechanical properties of structured sandwich composites, including flexural strength, impact strength, and compressive strength.

Experimental study of corrosion inhibition of RCC element using glass FRP mats

The corrosion of steel reinforced bars has been the main cause of affecting the strength of structural elements. An investigation on corrosion inducement at large scale on reinforced concrete beams by impressed current technique and their strengthening using Glass Fibre Reinforced polymer sheets. 5 Beams (1 uncovered + 4 covered with GFRP mats having different patterns) have been provided an accelerated environment to corrode, then tested to structural failure. The accelerated corrosion has been performed by dipping the beam into 5% NaCl solution upto half depth so as to target only the bottom rebar. The cathode has been fixed in the tub along with the beam as anode. An external power supply has been provided to supply a constant voltage of 15 V. One beam of each pattern and one controlled beam have been subjected to accelerated corrosion regime. After 150 hours of accelerated corrosion the beams have been subjected to Rebound hammer and Ultrasonic pulse velocity test i.e. non-destructive testing. After this beams have been subjected to Destructive testing like centre-point load flexure test. The decrease in area of steel reinforcement has been calculated using Faraday’s Law. Since the presence of Chloride ions in de-icing salts is the major cause the breakdown of the passive layer which is responsible to initiate corrosion. It only takes place if chlorides, oxygen and moisture are present in sufficient quantities at the level of reinforcing steel. Glass Fibre Reinforced polymer sheets have been sheathed around beams to protect and strengthen them from the loss of shear strength and confinement due to the corrosion of stirrups. Glass FRP’s are unaffected by electrochemical and electromechanical degradation. GFRP’s have corrosive inertia for aggressive corrosive effects of acids, alkalis, salts and similar aggregates under a wide range of temperatures. GFRP’s can be applied on the surface of concrete with the little apprehension of environmental degradation. Moreover, the FRP wraps provide a protective layer that may resist further corrosion of steel.

Pyrene‐Based Polyimide Covalent Organic Framework with Temperature‐Dependent Fluorescence

AbstractThe synthesis of a fluorescent covalent organic framework (COF) using perylene and pyrene building blocks (PEPy‐COF), via a one‐pot condensation reaction is reported. PEPy‐COF is crystallized into 2D nanosheets with a cubic and prismatic crystalline morphology and demonstrates structural stability at temperatures up to 500 °C. The structural morphology is confirmed using X‐ray diffraction and atomic‐level simulations. These 2D porous polymer sheets form a tetragonal framework that is found to have a high specific surface area of 772 m2 g−1. Based on the definition of porous materials, the network is mesoporous with an observed pore size of 3.03 nm, which is in good agreement with the material's calculated pore size. The experimentally obtained HOMO‐LUMO band gap is 2.62 eV, confirming the semiconducting nature of PEPy‐COF. PEPy‐COF emits a shiny blue luminescence under UV and visible light. This luminescence intensity is temperature‐dependent in solvents with different polarities and dielectric constants demonstrating that the PEPy‐COF has potential use in a wide range of temperature‐sensing devices. The fluorescence intensity ratio is similar for different temperatures under ultra‐sound conditions and varying solvents.

Hierarchically resistive skins as specific and multimetric on-throat wearable biosensors.

Resistive skin biosensors refer to a class of imperceptible wearable devices for health monitoring and human-machine interfacing, in which conductive materials are deposited onto or incorporated into an elastomeric polymeric sheet. A wide range of resistive skins has been developed so far to detect a wide variety of biometric signals including blood pressure, skin strain, body temperature and acoustic vibrations; however, they are typically non-specific, with one resistive signal corresponding to a single type of biometric data (one-mode sensors). Here we show a hierarchically resistive skin sensor made of a laminated cracked platinum film, vertically aligned gold nanowires and a percolated gold nanowire film, all integrated into a single sensor. As a result, hierarchically resistive skin displays a staircase-shaped resistive response to tensile strain, with distinct sensing regimes associated to a specific active material. We show that we can, through one resistive signal, identify up to five physical or physiological activities associated with the human throat speech: heartbeats, breathing, touch and neck movement (that is, a multimodal sensor). We develop a frequency/amplitude-based neural network, Deep Hybrid-Spectro, that can automatically disentangle multiple biometrics from a single resistive signal. This system can classify 11 activities-with different combinations of speech, neck movement and touch-with an accuracy of 92.73 ± 0.82% while simultaneously measuring respiration and heart rates. We validated the classification accuracy of several biometrics with an overall accuracy of >82%, demonstrating the generality of our concept.

The analysis of the bond strength between natural fiber reinforced polymer (NFRP) sheets and concrete

This study was conducted to develop an empirical model for predicting the bond strength between Natural Fiber Reinforced Polymer (NFRP) sheets and concrete. This was achieved through the production of 22 concrete block specimens with a size of 100 mm × 100 mm × 300 mm, having a single longitudinal reinforcing bar with a diameter of 10 mm in the center of its cross-section and a pre-existing crack in the middle of its length on 2 opposite sides. NFRP composites with a size of 50 mm × 240 mm were subsequently applied to both sides containing a crack. It is important to note that the NFRP was produced from fabric using 4 different types of fibers including jute, silk, pineapple, as well as dense and non-dense abaca fibers. Moreover, three different types of bonding adhesives were applied to bond the NFRP composite produced from abaca fiber to the concrete surface, and these include the standard epoxy resin, polyester resin, and thixotropic epoxy resin. Meanwhile, those produced using other types of fibers only required the standard epoxy resin. The NFRP was also made with different numbers of fabric layers ranging from 1 to 3, thereby, resulting in different thicknesses for the sheets. A tensile load was later applied through both ends of the reinforcing bar to rupture the NFRP sheets. It is pertinent to state that the bond strength model was proposed as a function of NFRP sheet thickness with due consideration for the influence of fiber density, fiber type, and bonding adhesive type. It was discovered that the bond strength calculated using the proposed model was very similar to the value obtained from the experiment. This study also determined the load-strain relationship and strain distribution along NFRP sheets. Moreover, the use of 2 and 3 layers of fabrics enhanced the bond strength by 118–350% and 312–400% respectively depending on the fiber and bonding adhesive types.

Strengthening Behavior of Rectangular Stainless Steel Tube Beams Filled with Recycled Concrete Using Flat CFRP Sheets

Recently, the adoption of recycled concrete instead of normal concrete as infill material in tubular stainless steel members has received great attention from researchers regarding environmental improvement. However, the flexural behavior of recycled concrete-filled stainless steel tube (RCFSST) beams that have been repaired/strengthened using carbon fiber-reinforced polymer (CFRP) sheets via a partial-wrapping scheme has not yet been investigated, and is required for a variety of reasons, as with any conventional structural member. Therefore, this study experimentally tested six specimens for investigating the effects of using varied recycled aggregate content (0%, 50%, and 100%) in infill concrete material of stainless steel tube beams strengthened with CFRP sheets. Additionally, several finite element RCFSST models were built and analyzed to numerically investigate the effects of further parameters, such as the varied width-to-thickness ratios and yield strengths. Generally, the results showed that using 100% recycled aggregates in infill concrete material reduced the RCFSST beam’s bending capacity by about 15% when compared to the corresponding control specimen (0% recycled aggregate), with little difference in the failure mode behavior. Pre-damaged RCFSST beam capacity showed significant improvement (43.6%) when strengthened with three CFRP layers. The RCFST model with a lower w/t ratio showed better-strengthening performance than those with a higher ratio, where, the models with w/t ratios equal to 15 and 48 achieved a bending capacity improvement equal to about 18% and 35%, respectively, as an example. Furthermore, the results obtained from the current study are well compared by those predicted using the existing analytical methods.

Parametric simulation of hybrid nanofluid flow consisting of cobalt ferrite nanoparticles with second-order slip and variable viscosity over an extending surface

Abstract This study explores the unsteady hybrid nanofluid (NF) flow consisting of cobalt ferrite (CoFe2O4) and copper (Cu) nano particulates with natural convection flow due to an expanding surface implanted in a porous medium. The Cu and CoFe2O4 nanoparticles (NPs) are added to the base fluid water to synthesize the hybrid NF. The effects of second-order velocity slip condition, chemical reaction, heat absorption/generation, temperature-dependent viscosity, and Darcy Forchheimer are also assessed in the present analysis. An ordinary differential equation system is substituted for the modeled equations of the problem. Further computational processing of the differential equations is performed using the parametric continuation method. A validation and accuracy comparison are performed with the Matlab package BVP4C. Physical constraints are used for presenting and reviewing the outcomes. With the increase in second-order velocity slip condition and unsteady viscosity, the rates of heat and mass transition increase significantly with the variation in Cu and Fe2O4 NPs. The findings suggest that the uses of Cu and Fe2O4 in ordinary fluids might be useful in the aerodynamic extrusion of plastic sheets and extrusion of a polymer sheet from a dye.

Numerical investigation and design of P-M interaction capacity of CFRP-jacketed hexagonal CFST short beam-columns

Hexagonal Concrete-Filled Steel Tubular (H-CFST) members are now widely recognized by engineers. A serious concern with these columns is the local buckling of thin-walled steel tubes, which Carbon Fiber-Reinforced Polymer (CFRP) sheets offer considerable help in eliminating this troublesome condition. The objective of this study is to evaluate the structural performance of short H-CFST columns stiffened by CFRP strips through nonlinear analysis and numerical simulation. First, the finite element (FE) models were validated against the previous test results, and a close agreement was achieved. Next, an organized parametric study was carried out to investigate the influence of a collection of vital parameters on the strength of the columns. The ultimate eccentric loads of the columns were computed, and the results were plotted as load-moment (P-M) interaction diagrams. The confining contact stress methodology between the steel tube and the concrete infill was in depth discussed, and it was found that the stress concentration is greater in CFRP-jacketed H-CFST columns than in bare ones, and its value is greatest in the corners. Based on the parametric study within the considered geometric and material ranges, using CFRP sheets effectively improves the confinement effect of steel tubes to the core concrete and enhances the strength of the columns by up to 35%. However, by using fully-wrapped CFRP layers, the columns could handle a maximum of 55% more load-carrying capacity. Finally, a modified design formula based on a unified theory was suggested to estimate the ultimate load and bending moment capacity of H-CFST short columns under eccentric loading.