Two-layer Laminate Research Articles

Decohesion of a polyolefin overlay from a substrate high density polyethylene layer by impact induced stress waves

High-density polythene (HDPE) is difficult to separate from food packaging waste for recycling because the packaging occasionally has multilayer plastic labels attached. Solvents are employed in the current separation techniques to remove undesirable layers from HDPE substrates. The possibility of separating HDPE via the impact-delamination phenomenon was explored both theoretically and experimentally. Using the cohesive zone model (CZM), the decohesion of layers in a model two-layer laminate made of HDPE and LDPE layers was studied theoretically. According to this study, stress waves emerge and severely damage the adhesion between the layers as a cutting blade strikes the laminate at speeds greater than 40 m/s. The damage can be enhanced by increasing the strike velocity and the apex radius of the blade. These findings show that a novel plastic delaminator that can cut and delaminate the laminates simultaneously can be designed. The proposed machine will feature two sets of blades with varying edge apex radii. One set of blades can be designed to cause the most adhesion damage while the other blades cut the laminate. This unique combination of cutting and delamination operations has several benefits, including less solvent waste and downstream processes, greater environmental friendliness, and faster HDPE separation.Laminates from HDPE milk bottles were cut using a high-speed cutter-blender with six blades to test the predicted results. The cut HDPE flakes were separated pneumatically. According to FTIR analysis and SEM, only a trace of adhesive was present on the cut and separated HDPE flakes.

A finite element analysis on the ballistic impact performance of two-layered laminate design inspired by teleost fish scales

A finite element analysis on the ballistic impact performance of two-layered laminate design inspired by teleost fish scales

Evaluation of Biophysical Properties of Potential Materials for the Manufacture of Protective Garments for Preterm Infants

Preterm infants, due to immature and dysfunctional skin, have increased water loss through the skin and consequently a decreased body temperature. In order to develop protective garments for preterm infants, it is important to select materials that will protect the child against water and heat loss. The authors are currently involved in the development of protective garments for premature babies, which are similar to baby clothes and contain a membrane that is partially permeable for vapor in combination with textile materials. This article presents the study of materials intended for the production of protective garments for pre-term infants. Samples of materials were investigated to determine biophysical comfort (tests of heat resistance, vapor resistance according to PN-EN ISO 11092:2014-11 and air permeability according to PN-EN ISO 9237) and porosity, surface mass in accordance with PN-EN 12127, and thickness in accordance with PN-EN ISO 5084. In order to determine the porosity of materials and to visualize the structure, tests on computer microtomography were carried out. The mechanical properties of the tested materials and the evaluation of the total hand value were characterized; the samples were tested on the KES device. The aim of this study was to select the most suitable fabrics for protective garments for premature infants to prevent excessive heat and moisture loss from the body, which can lead to hypothermia. For laminates, the optimal results of vapor resistance and heat resistance were obtained for laminate (15 g·m−2 PE foil + 15 g·m−2 PP non-woven), with a level of thermal resistance of 0.0766 m2·K·W−1 and vapor resistance of 188.729 m2·Pa·W−1, and for laminate (15 g·m−2 PE foil + 10 g·m−2 PP non-woven), with a level of thermal resistance of 0.0683 m2·K·W−1 and vapor resistance of 164.085 m2·Pa·W−1. For knitted fabrics, knitwear single cotton 155 g·m−2 showed the highest thermal resistance (0.0296 m2·K·W−1), and knitwear interlock polyester 120 g·m−2 showed the lowest thermal resistance (0.0179 m2·K·W−1). Knitwear cotton 120 g·m−2 had the highest water vapor resistance (8.402 m2·Pa·W−1), while knitwear interlock polyester 130 g·m−2 sample had the lowest resistance (6.356 m2·Pa·W−1). Garments for premature babies should have moisture barrier properties and high thermal insulation. They should also be characterized by optimal air permeability properties. Sample two-layer laminate (15 g·m−2 PE foil + 15 g·m−2 PP non-woven) had the best vapor resistance and thermal insulation properties. Moreover, this sample was characterized by good air permeability and surface weight compared to the other laminate samples. During the design of garments for premature babies, it is important to reduce the surface weight to as low as possible. Among the knitted fabrics, a knitwear single cotton 120 g·m−2 knitwear polyester interlock 120 g·m−2 was selected for having the best THV or tactile comfort. In addition, these knits were chosen for their lower surface weight. Based on the conducted tests, two-layer laminate (15 g·m−2 PE foil + 15 g·m−2 PP non-woven), the knitwear single cotton 120 g·m−2, and knitwear polyester interlock 120 g·m−2 were selected for further research.

Low-velocity impact behavior of carbon woven laminates after exposure to varying temperatures

The present study reports the low-velocity impact (LVI) performance of carbon woven reinforced polymer (CWRP) composites with varying temperatures. The fabrication of carbon woven lamina and carbon woven reinforced two-layered laminate (named CWRP-1 and CWRP-2) was done using a vacuum-assisted resin transfer molding (VARTM) process. CWRP-1 samples were tested at varying impact velocities of 1, 2, 3, and 4 m/s at −25, 25, and 50 °C for each incident velocity. CWRP-2 samples were tested at room temperature at varying incident velocities to determine the effect of multiple woven layers. The impact resistance of the first-crack load, peak impact load, and absorbed energies were recorded and evaluated under different loading conditions. In addition, the Weibull probability method is adapted to forecast failure behavior as a function of load. Visual inspection, optical microscopy, and scanning electron microscope (SEM) images were used to assess the damage pattern and failure morphologies in forecasting the failure phases during LVI. The low-velocity impact behavior of CWRP-1 at −25 °C with various velocities was shown to be random due to the polymer matrix freezing condition. The softening of the resin matrix at 50 °C is responsible for the difference in damage tolerance. The relevance of multiple layered composites for better impact resistance characteristics was demonstrated during testing of CWRP-2 at room temperature. Overall, the results of this experiment showed that CWRP lamina and laminates are highly sensitive to the impact velocities and external temperatures.

Number of layer effect of abaca fiber as natural FRP material for shear-strengthened reinforced concrete beam

In this paper, an experimental study was carried out to evaluate the number of layer effect of abaca fiber composite as natural reinforced polymer (NFRP) material for shear-strengthened reinforced concrete (RC) beams. Two externally bonded shear-strengthened beams with a different number of NFRP layers and a sound beam as a control beam were prepared. The test was conducted by applying two axial loads on the beam. The results showed that the use of one-layer and two-layer of abaca fiber composite as NFRP material for the shear-strengthened beam increased 9.78% and 9.92% of maximum load compared to sound beam respectively. Abaca fiber composite NFRP material contributed 11% and 18.57% of the total maximum shear load for one-layer and two-layer laminates respectively. In addition, externally bonded shear-strengthened beams affected the crack pattern and deflection value. However, debonding failure of NFRP laminates occurred in two-layer of the NFRP shear strengthened beam. It caused the beam did not work optimally.

Influence of Technology Process on Responsiveness of Footwear Nonwovens

Abstract Nonwovens represent a part of technical textiles that are used for clothing (“cloth tech”). Nonwovens are also used in the footwear industry mainly for functional purposes, where the aesthetic properties are not of great importance. They are mainly used for support and reinforcement of footwear. All three groups of textiles are used for footwear, i.e. woven fabrics, knitted fabrics and nonwovens that are produced directly from fibres, yarns or threads mainly from chemical fibres and in a small proportion from natural fibres. Footwear textiles need to have good mechanical properties (at compressive loading), abrasion resistance, permeability properties and heat resistance. These properties are in close connection with the nonwoven structure or composite materials. The basic intention of the presented research was to analyse the influence of the technology process on nonwovens for footwear responsiveness. Analysed footwear nonwovens in the presented research were on one side coated but on the other side consisted of a two-layer laminate. For this purpose, two different technological processes were used (coating and lamination). The results of the presented research showed that laminated samples express higher elastic recovery at compressive loading than coated samples. The treatment does not have an important influence on elastic recovery at compressive loading. Laminated samples express higher water permeability and lower absorption of water than coated samples, even after 24 hours of treatment in distilled water and compressive loading. The treatment of specimens in distilled water for 24 hours and compressive load of 789.6 N does not have an important influence on elastic recovery at compressive loading, water vapour permeability, air permeability and absorption of analysed samples. Air permeability could not be measured on coated samples.

Characteristics of Laminates for Car Seats

Abstract In the presented research, 11 different laminates were compared, 8 of them were two-layered 3 of them were three-layered laminates. The laminates that were analyzed vary by the type of face-side textile material (knitted and nonwoven textiles), density and thickness of the foam, and specific properties (higher air permeability and low-emission foam). Depending on the different types of laminates, different laminating processes are used: hot-melt, flame, and powder laminations. The purpose of the presented research is to analyze the basic characteristics of the different laminate structures. Properties that are important for these types of laminates are the number of layers, areal density, thickness, resistance to rubbing, fire resistance, water vapor permeability, air permeability, breaking force and extension, thermal conductivity, and stratification. We found that the properties of laminates were not affected by the density and thickness of the foam. Nonwovens and other laminate components do not perform because they have lower abrasion resistance and lower tensile strength than knitted fabrics as the face layer. Knit laminates have good abrasion resistance, high air permeability, and water vapor permeability. Both are self-extinguishing to the first or second mark. Three-layered laminates have lower thermal conductivity and air permeability than two-layered laminates.

Simulation of wrinkling in incompressible anisotropic thin sheets with wavy fibers

A two-dimensional plate theory is derived for incompressible transversely isotropic fiber-reinforced materials with wavy fibers. Single-layer plates and two-layer laminates are considered. Numerical simulations of axially loaded rectangular sheets in the post-buckling regime illustrate the marked effect fiber waviness has on both the wrinkling patterns and the effective axial stiffness. For fibers oriented along the loading axis, increased waviness tends to decrease the axial stiffness. Conversely, for fibers oriented transverse to the loading direction, increased waviness tends to increase stiffness.

Deformation behaviour of advanced textile composites with auxetic structure

The advanced composites – laminates, composed of auxetic and non-auxetic layers, were developed and subjected to tensile loading tests to characterize their deformation behaviour. The two-layer laminates were composed of the polymer foam with auxetic cellular structure and the conventional knitted fabric bonded together by the rubber-based adhesive, based on polymer binder, resins, additives and flammable organic solvents. All base materials, structured foams and laminates were tested. The influence of the adhesive on mechanical properties of the knitted fabric was also evaluated. The results of the study show that the cheaply fabricated laminates of knitted fabric reinforced by structured Ethylene-Vinyl Acetate (EVA) foam offer stiffness enhancement and decrease of the Poisson's ratio of the conventional fabric. The laminates also limit fabric warping during the deformation, thus increasing its stiffness. This behaviour can be beneficial in many applications in the textile industry by enhancing properties in durability, comfort and support.

Solvent Absorption and Dissolution Kinetics Modelling for the Chemical Recycling of Waste Plastic Laminates

The Philippines is expected to have an increase in consumption of waste plastic laminates known as sachets, composed of polyethylene (PE) and polyethylene terephthalate (PET) and used in various food and non-food consumer goods. The increase in demand of these sachets has led the country to become one of the top ocean polluters worldwide. Chemical recycling- specifically selective dissolution and reprecipitation- is seen as one viable option for the recovery of these polymers. In this study, the absorption and dissolution kinetics of D-limonene, a potential candidate solvent, in the two-layer (2LL) and three-layer (3LL) laminates were modelled and analyzed for the design of separation equipment to recovery PE. The absorption of limonene for both laminates was observed to initially follow Fickian diffusion, but plateaus when the dissolution rate becomes comparable with the solvent diffusion rate. The dissolution of the 3LL almost closely follows Fickian behavior, while 2LL initially follows Fickian behavior. Deviations from Fickian dissolution may be attributed to the difference in swelling behavior between the non-uniform solvent-polymer diffusion layer and the glassy polymer layer.

Multilayer Backsheet Characterization Using Diffusion Experiments and Optimization Method for Water Diffusion Simulation Inside the Photovoltaic Module

Photovoltaic (PV) modules are expected to be durable against exposure to outdoor environments for prolonged time durations. One of the primary causes for the loss of durability is water exposure. Water concentration prediction within the PV module is challenging under the varying environmental conditions as well as the multilayer nature of the backsheet. Therefore, there is a need for systematic multilayer water diffusion characterization of backsheet as well as to incorporate the varying environments in the water diffusion simulations of the PV module. In this article, backsheet is considered as a two-layer laminate whose water diffusion parameters were determined using both water diffusion experiments (without separation of each layer) and an optimization technique. The gravimetric technique was used to measure experimental water mass uptake of the backsheet, whereas Fick's second law based diffusion model was used to predict numerical water mass uptake. An optimization technique was used to determine the water diffusion and solubility coefficients that minimized the difference between the numerical and experimental water mass uptake. The optimized water diffusion and solubility coefficients in the test range of 24–50 °C reasonably fitted the Arrhenius rate equations. Backsheet was also considered as a homogeneous configuration that was used to determine the effective water diffusion parameters. These effective parameters were found to be significantly different from the optimized parameters of the two-layer backsheet model. Water diffusion simulations with a commercial PV module exposed to outdoor environment showed significant differences in the water concentration between the two-layer and homogeneous backsheet models.

Finite elastic wrinkling deformations of incompressible fiber-reinforced plates

A two-dimensional plate theory, valid for finite elastic deformations with small strains, is derived for incompressible, fiber-reinforced materials. Single-layer plates and two-layer laminates are considered. Numerical simulations illustrate the substantial effect that fiber reinforcement has on wrinkling patterns in the sheet.

Effects of Package Atmosphere and Storage Conditions on Minimizing Risk of Escherichia coli O157:H7 in Packaged Fresh Baby Spinach

Packaged fresh spinach has been associated with outbreaks of illness caused by Escherichia coli O157:H7. The purpose of this study was to assess the behavior of E. coli O157:H7 in packaged baby spinach in response to storage conditions of temperature and package atmosphere and including effects of inoculation level, spinach leaf damage (cut leaves), internalized or leaf surface contamination, exposure to hypochlorite sanitizer, and package size. Behavior of E. coli O157:H7 inoculated at 2 and 4 log CFU/g on spinach packaged in polymer bags composed of a two-layer laminate (polypropylene and polyethylene) and stored under atmospheres of 20% O2-3% CO2 and 0% O2-15% CO2 (aerobic and anaerobic, respectively) was assessed at 5, 7, 12, and 15°C for up to 14 days. Growth kinetics were calculated using DMFit software. Temperature decreases progressively diminished growth or survival of the pathogen, and an aerobic package atmosphere resulted in longer lag times (4 to 6 days) and lower population levels (0.2 to 1.4 log CFU/g) compared with the anaerobic atmosphere at 15°C. Internalized contamination, leaf cuts, or exposure to 100 ppm of hypochlorite did not result in changes in pathogen behavior compared with controls; however, a growth minimization trend consisting of longer lag times and lower population levels was repeatedly observed in the aerobic compared with the anaerobic package atmospheres. In contrast, growth of indigenous mesophiles and Enterobacteriaceae was unaffected by package atmosphere. Spinach stored at 5 to 7°C in two sizes (5 and 16 oz) of polyethylene terephthalate clamshell packages with ambient air atmospheres was more likely to progress to lower-oxygen conditions in 16-oz compared with 5-oz packages after 7 days of storage (P < 0.05). Practices to maintain aerobic conditions within the package, as well as storage of the package at low temperature, are ways to limit growth of E. coli O157:H7 in packaged spinach.

Eco-efficiency analysis of an innovative packaging production: case study

The article presents a two-dimensional comparison of the alternative manufacturing processes of laminates used in food industry packaging. The main aim of the presented study was an assessment of potential environmental impacts occurring during the production of two-layer laminates containing a patented polypropylene film Metallyte™ 28UBW-ES and the hitherto used pap/LDPE/Al/LDPE multilayer laminates. The environmental assessment was supplemented by a cost calculation with special regard to the investment required for the production of the two-layer laminates. In the research both the life cycle assessment and the life cycle cost methods were applied. Based upon the obtained environmental impact indicator and the discounted costs the eco-efficiency indicator was determined. The results of the comparative analysis are shown on a two-dimensional eco-efficiency diagram. Based on the conducted study it was found that replacement of traditional packaging materials by laminates containing the Metallyte™ 28UBW-ES structure is justified. This is illustrated by a higher eco-efficiency indicator. The difference in the costs between the manufacturing processes under analysis is relatively small. However, when it comes to the environmental impact, there is a clear disproportion in favor of the two-layer laminates.Graphical abstract

The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites

The free-edge effects and relative layer shifting in the interlaminar and intralaminar stresses of plain woven composite laminates under uniaxial extension is investigated numerically using a finite element approach. A computational framework of the free-edge problem for periodic structures with finite width is applied to woven laminates. First, two-layered laminates with three different shifting configurations are studied considering repeating unit cells simulating finite and infinite width. For each configuration, two different widths are considered by trimming the model at different locations in order to investigate different free-edge effects. Then, two four-layered laminates with no shifting and a maximum shifting configuration are analyzed to illustrate the effect of neighboring layers in the stresses. For each shifting configuration, different delamination mechanisms are expected. When considering more layers, it is found that the stacking configuration affects the state of stress and the free-edge effects depending on the shifting. In general, a different behavior than that of unidirectional tape laminates is found, since the interlaminar and intralaminar stresses can be higher than those generated at the free-edges. Particularly, for the maximum shifting configuration results are in agreement with experimental results in the literature where no debonding between yarns was observed at the free-edges.

Orthotropic material orientation optimization method in composite laminates

This paper proposes a optimization method that is capable of simultaneous design of multiple layers in a composite laminate with respect to multiple objective functions. The optimization process obtains a continuous orientation of an orthotropic material for each layer of the laminate. Each layer by itself is a single design domain, which allows multiple domains to be stacked in various orientations. Multiple optimization objectives are considered resulting in layers that perform different functions. The layers are modeled within a three-dimensional structure and by discretizing the structure using three-dimensional elements, the interaction between individual layers can be modeled. This also allows the optimization method to obtain a three-dimensional orientation vector. In this study, the individual layers are assumed to be thin, limiting the orientation vector to the mid-plane of the layer. The optimization model is tested on a two-layer laminate in which one layer is optimized for thermal control by directing heat toward specified sections while shielding other sections and the second layer is optimized to reduce the total deformation of the laminate structure that results from the thermal load. The results of simultaneous optimization for both layers are shown for several different configurations of boundary conditions.

Double contact analysis of multilayered elastic structures involving functionally graded materials

This paper analyzes the frictionless double contact problem of a two-layer laminate pressed against a homogeneous half-plane substrate by a rigid punch. The laminate is composed of a homogeneous elastic strip and a functionally graded layer, perfectly bonded along their interface. The mechanical properties of the graded layer are modeled by an exponentially varying shear modulus and constant Poisson’s ratio. Both the governing equations and the boundary conditions of the double contact problem are converted into a pair of singular integral equations by Fourier integral transforms, which are numerically integrated by Chebyshev–Gauss quadrature. The contact pressure and the contact size at both the advancing and the receding contact interface are eventually obtained by an iterative algorithm, developed from the method of steepest descent. Extensive parametric studies suggest that it is possible to control contact stress and contact size by introducing functionally graded materials into multilayered elastic structures.

Uniaxial compressive stability of laminated composite plate with localised interfacial degeneration

Motivated by general observation that it is practically impossible to achieve a perfect attachment between two originally separated materials, this paper examines numerically the influence of localised imperfect bonding at interface on the buckling response of fully fixed laminated composite plates, in the existence of uniaxial compression. The present work focuses on the buckling analysis of a two-layered laminate using the finite element formulation, in which each layer was meshed employing a locally contributing lamina sub-element, whereas the interface lied in between was modelled using a well-defined virtually zero-thickness interface element. To simulate the interfacial degeneration, a degeneration ratio R was conveniently prescribed. The present work has an advantage of permitting the simulation of deteriorated interface in a locally perturbed manner, differs from existing literatures that modelled mostly in a global sense. It is found from the current study that the normalised critical buckling load decreases, which indicates an increased degree of instability, corresponding to the rise in the degeneration ratio. Also, delaminated condition (R = 1), either isolated or otherwise, is the most critical scenario with an approximately 70% performance discount from that of R = 0·9. There exist, in addition, a variety of stability reduction trends when inducing different fibre orientations for the top lamina relative to that of the bottom. High dependencies of buckling modes on the degenerated area (Ar) and distance ratios () have also been exhibited.

Effect of the Process of Lamination Microporous Nanofiber Membrane on the Evaporative Resistance of the Two-Layer Laminate

This thesis deals with the assessment of the effect of the process of lamination microporous nanofiber membrane on the overall evaporative resistance of the two-layer laminate. For most multi-layer materials, lamination process is due to the deterioration of some properties of the whole laminate, particularly to the increase of the evaporative resistance. The authors of this thesis investigate the effect of the lamination primarily on the evaporative resistance of two-layer laminates. The study deals with the relations of volume porosity with the values of the evaporative resistance of the laminate too. In this thesis are both measured the separated layers of selected materials (upper material and the membrane), then the surface materials with the coated lamination points and subsequently created two-layer laminates.

Exponential Basis Functions in solution of laminated structures

In this paper a new method for solution of static two-dimensional laminates has been proposed. A series of Exponential Basis Functions (EBFs) have been used to satisfy the governing equations within each layer. Compatibility and equilibrium conditions at the interfaces of the layers, with isotropic or orthotropic properties, are rigorously satisfied through defining a characteristic problem. The solution of such a characteristic problem yields to a set of spectral basis functions through which one may obtain a clear insight to the modes governing the displacement field. For further use, we present simplified relations for single-layer and two-layer laminates. The boundary conditions at the ends of the laminate are satisfied by a suitable discrete transformation in a collocation style. With such an approach one can solve problems with variety of end conditions. Excellent agreement is observed between the results of this work and some benchmark problems. Some more problems are solved as new benchmarks for further studies.