High-density Polyethylene Layer Research Articles

Study on mode properties of GaAs-based hybrid plasmonic terahertz waveguides

Terahertz (THz) fields are increasingly being used to address the critical challenges associated with achieving high data rates and rapid communication. In this study, a hybrid plasmonic THz waveguide is designed and analysed operating in the 2.5–3.5 THz frequency range. The waveguide is constructed using gallium arsenide as the high-refractive-index core, surrounded by aluminium arsenide and silver placed on a high-density polyethylene (HDPE) substrate. Graphene is strategically positioned between the HDPE layers to enhance light confinement. The mode properties of the proposed waveguide are simulated with Comol Multiphysics using the finite-element method and show unique characteristics. Observation of the simulated results at 2.5–3.5 THz reveals a high effective refractive index of 3.79, a maximum effective mode area of 1.88 mm2, a high birefringence of 0.2, a low dispersion of 0.10 ps THz−1 cm−1, a high mode field diameter of 15.8 mm, a high beat length of 123 mm and a low confinement loss of 1.79 × 10−9 mm−1. These features make the proposed waveguide suitable for applications in photonic integrated circuits for THz communications.

Multi-scale coupling numerical modeling of metallic strip flexible pipe during reel-lay process

Complex plastic deformation and local buckling may occur due to the nonlinear contact between the pipe and drum in the offshore pipeline laying by reel-lay method. In this paper, material performance tests are carried out to obtain the nonlinear stress-strain constitutive models for high density polyethylene (HDPE) material and steel strip. Meanwhile, full-scale tensile tests are also conducted to acquire the tension-strain correlation of metallic strip flexible pipe (MSFP). Then, shell element and solid element are combined to establish an ABAQUS multi-scale finite element model (FEM) for MSFP under the coiled laying condition. The proposed multi-scale FEM consists of three components, i.e. two simplified components and one fine component, which could accurately and efficiently simulate the mechanical properties of flexible pipe under the coiled laying condition. The results indicate that: due to the radial extrusion restriction of spiral steel strips, the Mises stress distribution of inner HDPE layer shows a more uniform spiral strip distribution than outer HDPE layer; the most dangerous condition for MSFP may be when it is just partially wound up on the drum; the effect of friction coefficient on the spiral steel strips seems obviously larger than the effects of traction force and drum diameter.

3D printed functionally graded foams response under transverse load

The applications of 3D printing are rapidly increasing in aerospace and naval applications. Nonetheless, 3D printing (3DP) of graded foams exhibiting property variation along the thickness direction is yet to be explored. In the current work, the different volume fractions of hollow glass micro balloon (GMB) reinforced high-density polyethylene (HDPE) composite based graded foams are 3D printed using the fused deposition modelling (FDM) technique. The bonding between successive layers and porosity distribution of these graded configurations are studied using micro-CT scan. Further, the 3D Printed functionally graded foams (FGFs) are tested for flexural response, and results are compared with numerical values. The micro-CT results showed delamination absence between the layers. In neat HDPE layers, porosity is not evident, while minor porosity creeps in the layers having the highest GMB content. Experimental results of the flexural test showed that the graded sandwiches exhibited better strength than the graded core alone. Compared to neat HDPE, the modulus of FGF-2 (H20–H40–H60) increased by 33.83%, implying better mechanical stiffness. Among all the FGFs, FGF-2 exhibited a better specific modulus. A comparative study of experimental and numerical results showed a slight deviation due to neglecting the induced porosity.

Compression behavior of concrete columns strengthened by a hybrid BFRP/HDPE tube coupled with a crumb rubber concrete cladding layer

A previous study proved that the confinement of fiber-reinforced polymer (FRP) effectively improves the load capacity and ductility of concrete columns. High-density polyethylene (HDPE) material, which exhibits excellent erosion resistance and high ductility, possesses enormous potential for strengthening structural columns. Based on the discussion, the combination of these two materials as hybrid confinement is investigated in this study. As an energy-dissipating material with excellent ductility, rubber concrete is employed in the hybrid strengthening method as an anti-collision layer. A novel composite system that comprises external FRP-HDPE confinement and an infilled rubber concrete layer is proposed in this study. An experimental test investigates its compressive strength, and three variables are considered, including the diameter of the HDPE tube, the layers of FRP sheets, and the addition of rubber particles in rubber concrete. The test results show that the ultimate compressive strength of specimens is improved with an increase in the diameter of the HDPE tube and layers of the FRP sheet, while the higher addition of rubber particles can reduce the compressive strength. However, these three variables have a positive effect on the deformation capacity of the specimens. A theoretical model is proposed for predicting the ultimate axial stress of specimens, which can provide a reference for designing this hybrid reinforcement.

Effect of Indenter Nose Shape and Layer Configuration on the Quasi-Static Perforation Behaviour of Metal-Plastic Laminates.

This study investigated the perforation resistance behaviour of metal–plastic laminates (MPLs) when they are indented by different nose shapes. Aluminium (Al) and HDPE (high-density polyethylene) layers were bonded with a suitable adhesive in an alternative manner to prepare bilayer and trilayer MPL configurations. Quasi-static perforation experiments were performed with hemispherical, conical and blunt indenters. The effects of nose shape, layer configuration and adhesive on the force–deformation profile, perforation resistance capacity and failure mechanisms were evaluated. The results indicate that for a monolithic layer, the blunt indenter showed the highest perforation energy capacity. The conical and blunt indenters facing Al backed by HDPE gave higher perforation energy. The hemispherical indenter facing HDPE backed by Al was found to be more effective in perforation resistance. Trilayer Al–HDPE–Al showed higher perforation resistance than HDPE–Al–HDPE. Circumferential cracking, radial symmetric cracking and shear plugging were the main failure modes for Al under hemispherical, conical and blunt indenters, respectively. The adhesive contributed to an increase in the perforation energy and peak force to failure in laminates. The adhesive was shown to detach from the Al surface after Al fracturing through crack propagation, and this effect was more pronounced when the indenter faced HDPE at the front of the laminate.

Structure and mechanical properties of a multilayer biomedical shaft tubing: effect of layer composition

Abstract Trilayer polymer tubes were manufactured through an extrusion process using Pebax 6333 and high density polyethylene (HDPE) as outer and inner layer, respectively. A maleic grafted linear low-density polyethylene (LLDPE) was used as the bonding layer or tie-layer. Three types of multilayer tubes were produced: (1) outer layer (Pebax) at 70% of the total wall thickness (WT), (2) outer layer at 90% of WT, and (3) outer layer at 20% of WT. The analysis of mechanical properties showed that the inner layer contributes to strength and rigidity of the tube while the outer layer provides flexibility. Melt rheology behavior for HDPE and Pebax were studied, and HDPE showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that HDPE layer is more sensitive to molecular orientation when extruded compared to Pebax material. Melting behavior for the tubes was investigated using dynamic scanning calorimetry (DSC). The tubes showed two melting temperatures: one associated with HDPE and one with Pebax. The HDPE peak showed a specific shift to a higher melting point for tubes as a result of molecular orientation during processing. Burst and compression testing were performed on the tubes and results demonstrated that the HDPE-rich extrusion showed the highest burst pressure and compression resistance.

Experimental investigation of the behavior of soil reinforced with waste plastic bottles under cyclic loads

The low natural degradation rate of plastic products makes the recycling or disposal of increasing post-consumer plastic materials, including Plastic Polyethylene Terephthalate (PET) bottles, a global concern. The current capacity of recycling programs for absorbing annual waste PET materials in environmentally friendly ways is limited. As a novel beneficial option, the cellular form of post-consumer bottles might act to provide sufficient confinement for infill soil and hence provide a technique by which the behavior of foundation beds under applied loads could be improved. In this study, a series of full-scale tests were conducted on unreinforced and PET (Plastic Polyethylene Terephthalate) bottle reinforced beds. For each test 100 cycles of 400 kPa load followed by 400 cycles of 800 kPa load was applied to the pavement through loading plate. Experiments were performed in a 2200 × 2200 × 1000 mm test pit on a 300 mm diameter circular loading plate. Three different sizes (i.e., different external diameters and heights) of waste plastic (PET) bottles filled with soil were tested as a reinforcing element. In some tests, a single layer of HDPE (high-density polyethylene) geogrid layer over bottles reinforced zone was examined. The results showed improvement in all reinforcing arrangement, although improvement was slightly higher for smaller bottles. For the reinforced case, a lower settlement accumulation rate and a higher resilient (elastic) settlement was observed compared to the unreinforced condition. In the case of lower cyclic loading (400 kPa amplitude), an average 42% improvement occurred for the three bottle-reinforced scenarios, however this value was 179% for higher cyclic loading (800 kPa), indicating more benefits of bottle-reinforcement in the case of critically loaded conditions. An extra layer of geogrid over the bottle-reinforced zone increases load distribution area and prevents distortion of bottles, leading to as much as 82% more reduction in soil settlement compared to the case without geogrid. The combined use of bottles and single geogrid layer eliminates the need to multilayer geosynthetic reinforcement usage, helps the economy of the project besides avoiding the high cost of waste bottle disposal.

Properties of core-half wrapped shell structure wood-polymer composites containing glass fiber-reinforced shells

Glass fiber (GF) is commonly applied as a filler in the preparation of polymer composites. Due to the presence of GF, composite mechanical performance, flame resistance, and thermal performance could be greatly improved. The influence of a GF-filled polymer shell layer was investigated relative to the morphology, mechanical, thermal, and fire flammability performance of the core-half wrapped shell structured wood high-density polyethylene (HDPE) composites prepared via co-extrusion. The use of the relatively less-stiff pure HDPE with high linear coefficients of thermal expansion (LCTEs) lowered the general thermal stability and modulus of the wood polymer composites (WPCs). Flexural and thermal expansion properties were improved for the GF-filled HDPE shells in comparison to the unmodified material, enabling a well-balanced performance of this novel core–shell material. Implementation of GF-modified HDPE or unmodified HDPE layers as a shell for WPC core remarkably improved the impact resistance of the co-extruded WPCs. In comparison with composites possessing unmodified HDPE shell, the flame resistance performance of the shell layer was slightly improved in case that the GF content was below 25 wt%. A slight decrease in composite general heat release and rate was discovered in case that the GF content was greater than 25 wt%.

Mechanical, flammable, and thermal performances of co-extruded wood polymer composites with core–shell structure containing barite-filled shells

Wood polymer composites (WPCs) with core–shell structure reinforced with barite (BA)-filled high-density polyethylene (HDPE) shell layer were successfully fabricated, and their thermal expansion and mechanical properties were thoroughly analyzed. The incorporation of BA improved the flexural properties and reduced the impact strength and linear coefficients of thermal expansion (LCTEs) of the resulting composites, in comparison with unmodified HDPE. The use of relatively rigid pure HDPE with high LCTE values reduced the overall thermal stability and modulus of the WPCs. Both flexural properties and thermal expansion were significantly enhanced for BA-filled HDPE shells compared to the unmodified material. Thus, the novel core–shell layer showed a well-balanced performance. The employment of BA HDPE or unmodified HDPE layers as the shell for the WPC core significantly enhanced the impact strength of the co-extruded WPCs. The tensile modulus for BA-filled composite was predicted by the PPA-based model.

Experimental evaluation of an expanded polystyrene (EPS) block-geogrid system to protect buried pipes

This study presents the results of experimental tests carried on buried uPVC (unplasticized polyvinyl chloride) pipes with an external diameter of 160 mm. The behavior of buried pipes in unreinforced and reinforced trenches by a single layer of HDPE (high-density polyethylene) geogrid and expanded polystyrene (EPS) geofoam block were investigated. To simulate vehicle wheel loadings, 500 cycles of repeated load respectively with an amplitude and frequency of 450 kPa and 0.33 Hz was applied to a loading plate placed over the trench surface. Pipe behavior under cyclic loadings were assessed using vertical diameter strain measurements, circumferential strains and pressures at the crown and springline. Additionally, settlement at the soil surface was measured throughout testing. The testing program is aimed at evaluating the role of different parameters influencing pipe behavior, such as embedded depth of the pipe, implementation of the EPS block and geogrid layer simultaneously and separately, and density, width and thickness of the EPS blocks. The results illustrate that the rate of changes in the pipe circumferential strain, vertical diameter strain and soil surface settlement, which increase rapidly in initial loading cycles, decreased as loading progressed. Based on the results, the density, width and thickness of implemented EPS blocks have an impact role in improving the behavior of buried pipes. The use of geogrid reinforcement with an EPS block with density of 30 kg/m3, thickness of 60 mm and width of 1.5 times the pipe diameter showed the most benefit when balancing vertical diameter strain, pipe crown strain, and soil surface settlement.

Friction spot lap joining of the anodized aluminium alloy 6061 with high-density polyethylene sheets

PurposeThe purpose of this paper is to join an anodized aluminium alloy AA6061 sheet with high-density polyethylene (HDPE) using friction spot process.Design/methodology/approachThe surface of AA6061 sheet was anodized to increase the pores’ size. A lap joint configuration was used to join the AA6061 with HDPE sheets by the friction spot process. The joining process was carried out using a rotating tool of different diameters: 14, 16 and 18 mm. Three tool-plunging depths were used – 0.1, 0.2 and 0.3 mm – with three values of the processing time – 20, 30 and 40 s. The joining process parameters were designed according to the Taguchi approach. Two sets of samples were joined: the as-received AA6061/HDPE and the anodized AA6061/HDPE.FindingsFrictional heat melted the HDPE layers near the lap joint line and penetrated it through the surface pores of the AA6061 sheet via the applied pressure of the tool. The tool diameter exhibited higher effect on the joint strength than processing time and the tool-plunging depth. Specimens of highest and lowest tensile force were failed by necking the polymer side and shearing the polymer layers at the lap joint, respectively. Molten HDPE was mechanically interlocked into the pores of the anodized surface of AA6061 with an interface line of 18-m width.Originality/valueFor the first time, HDPE was joined with the anodized AA6061 by the friction spot process. The joint strength reached an ideal efficiency of 100 per cent.

HDPE/EVOH Multilayered, High Barrier Films for Flexible Organic Photovoltaic Device Packaging

Transparent films composed of 65 alternating layers of high density polyethylene and ethylene/vinyl alcohol copolymer were produced and evaluated for their oxygen and water vapor barrier performanc...

One dimensional imager of neutrons on the Z machine.

We recently developed a one-dimensional imager of neutrons on the Z facility. The instrument is designed for Magnetized Liner Inertial Fusion (MagLIF) experiments, which produce D-D neutrons yields of ∼3 × 1012. X-ray imaging indicates that the MagLIF stagnation region is a 10-mm long, ∼100-μm diameter column. The small radial extents and present yields precluded useful radial resolution, so a one-dimensional imager was developed. The imaging component is a 100-mm thick tungsten slit; a rolled-edge slit limits variations in the acceptance angle along the source. CR39 was chosen as a detector due to its negligible sensitivity to the bright x-ray environment in Z. A layer of high density poly-ethylene is used to enhance the sensitivity of CR39. We present data from fielding the instrument on Z, demonstrating reliable imaging and track densities consistent with diagnosed yields. For yields ∼3 × 1012, we obtain resolutions of ∼500 μm.

Management of toxic and hazardous contents of oil sludge in Siri Island

Sirri Island is one of the most important islands in Iran where contains massive amounts of crude oil reservoirs and is a crude oil exporting and storage spot. Petroleum sludge wastes produced by the refineries are deposited in outdoor 2-ha open pits. 30 sludge samples from different depot locations were conducted in 3-time intervals and mixed with each other to form one homogenized sample. The sample was treated by solvent extraction method using methyl ethyl ketone as an efficient polar solvent in order to recover the valuable hydrocarbon and oil. About 99.8% of the oil was recovered and determined to reach almost the same quality as the exportable crude oil of Sirri Island. The sediments were also tested for size distribution range and titled as fine-grained soil. Toxicity characteristics leaching procedure test was conducted on the residuals to determine whether the waste is categorized as toxic and hazardous. The industrial waste evaluation model used in the current work suggested different leachate concentrations (10%, 30%, 50%, 70% and 90% of total leachate) based on toxicity characteristics leaching procedure for different probable leaching scenarios. The surface and subsurface regional conditions such as depth to underground water table, climate condition, subsurface pH, soil texture and material were defined to the model as well. Then, the model simulated 10000 possible runs considering the leaching procedure, contaminant concentrations, maximum contaminant limits and surface and sub-surface conditions. The final outcomes regarding heavy metals results showed that nickel, chromium and vanadium were protective under composite liner while cobalt and lead were not safe under such liner and need proper treatment before landfilling. As the final step, the size and details of landfill were designed. The landfill was selected as a square with side and depth of 55m and 3m respectively. The composite liner consisted of 1.5mm high density polyethylene layer with 50cm compacted clay liner of 10-7 cm/s hydraulic conductivity underneath.

Semi-insulating GaAs based detector of fast neutrons produced by D–T nuclear reaction

We have examined semi-insulating (SI) GaAs detectors with high density polyethylene (HDPE) conversion layer by a mono-energetic neutrons with kinetic energy of 16.755 MeV generated by a deuterium—tritium nuclear reaction. First, the influence of HDPE layer thickness on the relative detection efficiency of fast neutrons was studied. The MCNPX (Monte Carlo N-particle eXtended) code has been used to support the analysis of the experiment. The theoretical optimum thickness of the conversion layer was determined to 1.9 mm using the MCNPX code. The HDPE conversion layers of various thicknesses, in the range from 50 μ m to 3200 μ m, were glued on the top Schottky contact of SI GaAs detector in the experiment. The neutron detection efficiency was evaluated from measured spectra and compared to results from simulations. The experimental data showed very good agreement with simulation results. Then the effect of active detector thickness modified by detector reverse bias on neutron detection efficiency was studied. Finally, the effect of the angle of irradiation on neutron detection efficiency was evaluated exhibiting decreasing tendency with increasing deviation from perpendicular direction of impinging neutrons.

Semi-insulating GaAs detectors with HDPE layer for detection of fast neutrons from D–T nuclear reaction

Bulk semi-insulating (SI) GaAs detectors optimized for fast-neutron detection were examined using mono-energetic neutrons. The detectors have an active area of 7.36 mm2 defined by a multi-pixel structure of a AuZn Schottky contact allowing a relatively high breakdown voltage (300 V) sufficient for full depletion of the detector structure. The Schottky contact is covered by a HDPE (high density polyethylene) conversion layer, where neutrons transfer their kinetic energy to hydrogen atoms through elastic nuclear collisions. The detectors were exposed to mono-energetic neutrons generated by a deuterium (D)–tritium (T) nuclear reaction at a Van de Graaff accelerator. Neutrons reached a kinetic energy of 16.8 MeV when deuterons were accelerated by 1 MV potential. The influence of the HDPE layer thickness on the detection efficiency of the fast neutrons was studied. The thickness of the conversion layer varied from 50 [Formula: see text]m to 1300 [Formula: see text]m. The increase of the HDPE layer thickness led to a higher detection efficiency due to higher conversion efficiency of the HDPE layer. The effect of the active detector thickness modified by the detector reverse bias voltage on the detection efficiency was also evaluated. By increasing the detector reverse voltage, the detector active volume expands to the depth and also to the sides, slightly increasing the neutron detection efficiency.

MCNPX simulations of the silicon carbide semiconductor detector response to fast neutrons from D–T nuclear reaction

Silicon Carbide (SiC) has been long recognized as a suitable semiconductor material for use in nuclear radiation detectors of high-energy charged particles, gamma rays, X-rays and neutrons. The nuclear interactions occurring in the semiconductor are complex and can be quantified using a Monte Carlo-based computer code. In this work, the MCNPX (Monte Carlo N-Particle eXtended) code was employed to support detector design and analysis. MCNPX is widely used to simulate interaction of radiation with matter and supports the transport of 34 particle types including heavy ions in broad energy ranges. The code also supports complex 3D geometries and both nuclear data tables and physics models. In our model, monoenergetic neutrons from D–T nuclear reaction were assumed as a source of fast neutrons. Their energy varied between 16 and 18.2 MeV, according to the accelerating voltage of the deuterons participating in D–T reaction. First, the simulations were used to calculate the optimum thickness of the reactive film composed of High Density PolyEthylene (HDPE), which converts neutral particles to charged particles and thusly enhancing detection efficiency. The dependency of the optimal thickness of the HDPE layer on the energy of the incident neutrons has been shown for the inspected energy range. Further, from the energy deposited by secondary charged particles and recoiled ions, the detector response was modeled and the effect of the conversion layer on detector response was demonstrated. The results from the simulations were compared with experimental data obtained for a detector covered by a 600 and 1300 [Formula: see text]m thick conversion layer. Some limitations of the simulations using MCNPX code are also discussed.

Mechanical behavior of pipe reinforced by steel wires under external pressure

Plastic pipe reinforced by helically cross-winding steel wire (namely PSP) is a novel kind of composite pipe which consists of an inner high-density polyethylene layer, steel wire layers and an outer polyethylene coating. PSP has the potential application as subsea pipeline. Based on numerical 2D ring model, proposed by Yong Bai, the wall thickness change, transverse shear deformation and pre-buckling deformation have been considered in the collapse investigation of PSP under external hydrostatic pressure. Based on finite element method, reinforced layers were taken as transverse isotropic material, and equivalent elastic modulus was obtained based on Halpin–Tsai model. It is shown that steel wires layer has little effect (just 0.2% difference) on the behavior of PSP under external pressure. The external pressure–ellipticity and external pressure–hoop strain curves derived from the theoretical method and finite element method are compared and show a good agreement (deviation of buckling pressure is 1.4%). Finally, maximum experimental external pressure values of two pipe specimens were obtained by increasing hydrostatic pressure in a closed cylinder. The results of theoretical analysis and finite element method are in great agreement with the experimental values.

PICS bags protect wheat grain, Triticum aestivum (L.), against rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Purdue Improved Crop Storage Bags (PICS) bags are hermetic containers consisting of two inner layers of high-density polyethylene (HDPE) surrounded by an outer woven polypropylene bag. They have proven effective in preventing losses of stored cowpea grain to the cowpea bruchid, Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae) and perform well with other dry grains attacked by several species of postharvest pests. We tested PICS bags against the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), a common stored grain pest. Storing rice weevil infested wheat in PICS bags arrested weevil population growth and preserved the grain well. The air surrounding infested wheat held in PICS bags had lower oxygen and higher carbon dioxide levels compared to the ambient atmosphere. Seed germination declined over time in infested PICS bags, but less so than did grain held in infested woven bags. Low-cost, durable, pesticide-free PICS technology offers an inexpensive, practical and useful way to protect wheat against rice weevil.

Bending Behavior of Reinforced Thermoplastic Pipe

Reinforced thermoplastic pipe (RTP) is a composite thermoplastic pipe, which is increasingly being used in oil and gas industry. In practical applications, RTPs inevitably experience bending during reeling process and offshore installation. The ovalization instability of RTP under pure bending was investigated. Several fundamental assumptions of RTP were proposed from the engineering application point of view. Then, based on nonlinear ring theory initially proposed by Kyriakides et al., the effect of transverse deformation through the thickness was introduced, and the ovalization growth of cross section during bending was studied according to nonlinear kinematics. The formulation was based on the principle of virtual work and was solved by a numerical solution. Inelastic material behavior of high density polyethylene (HDPE) was included, and a simplified method was proposed to simulate the behavior of fiber reinforced layer. A detailed Abaqus model was established using solid and truss elements to simulate the HDPE layer and reinforced fiber, respectively. The results obtained from the theoretical method were compared with Abaqus simulation results and test data of verification bending experiment and the results show excellent agreement. The proposed methods are helpful for RTP's engineering applications.