Multilayer Composite Materials Research Articles

Compositional analysis of multilayered plastic constituents and constituent mixtures using benchtop 1H NMR spectroscopy.

Multilayered plastics are widely used in food packaging and other commercial applications due to their tailored functional properties. By layering different polymers, the multilayered composite material can have enhanced mechanical, thermal, and barrier properties compared to a single plastic. However, there is a significant need to recycle these multilayer plastics, but their complex structure offers significant challenges to their successful recycling. Ultimately, the use and recycling of these complex materials requires the ability to characterize the composition and purity as a means of quality control for both production and recycling processes. New advances and availability of low-field benchtop 1H NMR spectrometers have led to increasing interest in its use for characterization of multicomponent polymers and polymer mixtures. Here, we demonstrate the capability of low-field benchtop 1H NMR spectroscopy for characterization of three common polymers associated with multilayered packaging systems (low-density polyethylene [LDPE], ethylene vinyl alcohol [EVOH], and Nylon) as well as their blends. Calibration curves are obtained for determining the unknown composition of EVOH and Nylon in multilayered packaging plastics using both the EVOH hydroxyl peak area and an observed peak shift, both yielding results in good agreement with the prepared sample compositions. Additionally, comparison of results extracted for the same samples characterized by our benchtop spectrometer and a 500-MHz spectrometer found results to be consistent and within 2wt% on average. Overall, low-field benchtop 1H NMR spectroscopy is a reliable and accessible tool for characterization of these polymer systems.

Characterization of the layer, direction and time-dependent mechanical behaviour of the human oesophagus and the effects of formalin preservation.

The mechanical characterization of the oesophagus is essential for applications such as medical device design, surgical simulations and tissue engineering, as well as for investigating the organ's pathophysiology. However, the material response of the oesophagus has not been established ex vivo in regard to the more complex aspects of its mechanical behaviour using fresh, human tissue: as of yet, in the literature, only the hyperelastic response of the intact wall has been studied. Therefore, in this study, the layer-dependent, anisotropic, visco-hyperelastic behaviour of the human oesophagus was investigated through various mechanical tests. For this, cyclic tests, with increasing stretch levels, were conducted on the layers of the human oesophagus in the longitudinal and circumferential directions and at two different strain rates. Additionally, stress-relaxation tests on the oesophageal layers were carried out in both directions. Overall, the results show discrete properties in each layer and direction, highlighting the importance of treating the oesophagus as a multi-layered composite material with direction-dependent behaviour. Previously, the authors conducted layer-dependent cyclic experimentation on formalin-embalmed human oesophagi. A comparison between the fresh and embalmed tissue response was carried out and revealed surprising similarities in terms of anisotropy, strain-rate dependency, stress-softening and hysteresis, with the main difference between the two preservation states being the magnitude of these properties. As formalin fixation is known to notably affect the formation of cross-links between the collagen of biological materials, the differences may reveal the influence of cross-links on the mechanical behaviour of soft tissues.

Multi-layer material combination for manufaturing stab-proof life jackets

In modern times, individuals working in aquatic environments such as fishermen, fishery inspectors, customs officers, and others require a device that offers protection against punctures and drowning. As a result, a multi-layer composite material consisting of para-aramid 200de woven fabric, Dyneema® SB31 coated plates, and foam was evaluated for the creation of a life jacket that combines stab-proof capabilities with anti-drowning features (stab-proof life jacket). The objective of the research was to determine the optimal number of layers and arrangement of the multi-layer composite materials that would meet the NIJ standard level 1 protection against punctures. The study findings demonstrated that utilizing both types of woven fabric and coated plates yielded the most desirable puncture resistance, considering the thickness and weight of the composite materials. The effectiveness of using only woven fabric ranked second, while relying solely on coated plates produced less satisfactory results. Placing the puncture-resistant material above the foam layer proved to be more effective than placing it beneath the foam layer in all three scenarios. These findings lay the groundwork for the design and development of stab-proof life jackets tailored to the needs of professionals in specific aquatic industries. Keywords: Puncture-resistant life vest, puncture-resistant, multi-layer composite, aramid, UHMWPE

Designed MoSe2 modified multi-layer hollow carbon fiber composite material achieves tunable electromagnetic wave absorption in the X and Ku bands

As a substitute for graphene-based carbon materials, carbon fiber (CF) based absorbing materials have enormous application prospects. Effective improvements have been made in solving the problems of heavy quality and complex preparation processes of ordinary absorbing materials. In order to obtain a flexible thin fiber membrane absorbing material with good stability and excellent performance, we prepared a multi-layer hollow carbon sphere/CF@MoSe2 with carbon fiber as the matrix, and controlled the microstructure through hollow carbon shell and MoSe2, and introduced transition metal chalcogenides to coordinate electromagnetic parameters. As a result, the hollow carbon sphere/CF@MoSe2 flexible composite film achieved a minimum reflection loss (RLmin) of −47.98 dB at a thickness of 2.5 mm, and an effective bandwidth (EAB) of 8.1 GHz at a thickness of 2.7 mm. The RLmin of the hollow carbon ball/CF composite film reached −45 dB at a thickness of 2.6 mm, and the EAB reached 3.2 GHz. The theoretical characterization results jointly prove the reason for the improved performance, and this study provides an experimental basis for a more in-depth exploration of the birth of new absorbing materials.

Effect of reduction rate on microstructure and properties of laminated steel/aluminium low density composites prepared by hot pressing

ABSTRACT A multi-layer composite material consisting of 316 L steel and Al6061 aluminium was prepared via hot pressing. The mechanical properties of this heterogeneous layered composite material were studied under various reduction rates. The results revealed that the overall performance of the material initially improved and then declined as the reduction rates increased. Notably, at a hot pressing temperature of 400°C, the material exhibited optimal performance at a reduction rate of 32%. Furthermore, finite element simulations of the material processing process were performed using ABAQUS software, and the stress-strain state was analysed. The findings indicated that the overall performance of the material is influenced by both the presence of intermetallic compounds (IMCs) at the interface and the shear stress at the interface. In comparison to the aluminium layer, the performance of the steel layer undergoes more pronounced changes at the same reduction rate.

Performance of Electromagnetic Properties of Carbon Fiber Reinforced and AuNPs Functionalized MWCNTs Doped Hybride Composites

The purpose of this article is to compare the electromagnetic absorption properties of carbon fiber layer composite materials produced separately using Au particles doped MWCNT added epoxy with pure MWCNT added epoxy resin. This new material, produced using MWCNT doped with Au particles, increases its radar absorption capability. And therefore the as-prepared electromagnetic absorber demonstrates enormous potential in future military and aviation applications. Multilayer composite materials, consisting of Au/MWCNT doped epoxy, MWCNT doped epoxy and pure epoxy, were produced by vacuum infusion method. Electromagnetic absorbing properties of the produced materials were determined with the Agilent brand 2-Port PNA-L Network Analyzer device by conducting transmission/reflection measurements in the frequency range of 3–18 GHz. The electromagnetic absorbing properties of the produced composite materials were taken in two different measurements, both with and without metal plate. Measurements were made using two horn antennas. Show that the produced MWCNT doped and Au/MWCNT doped carbon fiber laminated composite material has good absorption behavior when used with metallic sheets and is good for RADOM applications at many points at 3–18 GHz.

Quantitative Detection of Defects in Multi-Layer Lightweight Composite Structures Using THz-TDS Based on a U-Net-BiLSTM Network.

Multi-layer lightweight composite structures are widely used in the field of aviation and aerospace during the processes of manufacturing and use, and, as such, they inevitably produce defects, damage, and other quality problems, creating the need for timely non-destructive testing procedures and the convenient repair or replacement of quality problems related to the material. When using terahertz non-destructive testing technology to detect defects in multi-layer lightweight composite materials, due to the complexity of their structure and defect types, there are many signal characteristics of terahertz waves propagating in the structures, and there is no obvious rule behind them, resulting in a large gap between the recognition results and the actual ones. In this study, we introduced a U-Net-BiLSTM network that combines the strengths of the U-Net and BiLSTM networks. The U-Net network extracts the spatial features of THz signals, while the BiLSTM network captures their temporal features. By optimizing the network structure and various parameters, we obtained a model tailored to THz spectroscopy data. This model was subsequently employed for the identification and quantitative analysis of defects in multi-layer lightweight composite structures using THz non-destructive testing. The proposed U-Net-BiLSTM network achieved an accuracy of 99.45% in typical defect identification, with a comprehensive F1 score of 99.43%, outperforming the CNN, ResNet, U-Net, and BiLSTM networks. By leveraging defect classification and thickness recognition, this study successfully reconstructed three-dimensional THz defect images, thereby realizing quantitative defect detection.

Preliminary Hybrid Joint Analysis for Aircraft Structures

Metal-composite joints, or hybrid joints are prevalent in aerospace structures due to their high strength and low weight. Such structures are usually found in areas where because of the load configuration, the use of composite materials is possible. Thereby, the analysis of such areas needs to consider both components, the metallic and the composite part. In this paper a hybrid joint is analyzed, consisting of a metallic stiffener, a multilayered honeycomb composite material, and joining fasteners, which constitute the joint between the isotropic and orthotropic materials. The present article has two main purposes: the first is to illustrate a pre-design procedure aimed to evaluate the load-carrying capability of a hybrid joint structure, thereby giving an estimate if the structure can withstand the given loading conditions; the second purpose is to present two types of finite element modeling techniques, one that captures the real geometric structure of the composite material and another which uses a simplified equivalent model, based on the desired level of evaluation of the composite material part. A comparison between the two models is made, highlighting the advantages and disadvantages of the two forms of evaluations. For the metallic parts - stiffener and fasteners, both static and fatigue analyses were performed, as fatigue failure represents the common service failure mode for this type of structural components.

Experimental determination of the interlayer fracture toughness of a composite material

Modeling the propagation of interlaminar defects in multilayer composite materials requires knowledge of the characteristics of the material under study associated with the fracture processes. The goal of the study is determination of the interlaminar fracture toughness in the case of normal traction (GIc). Finite element modeling of testing was carried out proceeding from the data obtained. The delamination process was modeled using the most common approaches within the finite element method: VCCT (virtual crack closure technique) and CZM (cohesive zone model), wherein the fracture toughness is used as the main parameter for the occurrence of delamination. The obtained data are compared with the experiment. To confirm the correctness of the obtained experimental data on the fracture toughness GIc, modeling of the process of compression testing of a strut-type specimen with a defect in the form of a through-the-width delamination was carried out. This problem includes a nonlinear static solution with buckling and subsequent post-buckling behavior, and, as a result, the spread of the delamination zone. The data obtained using finite element modeling are consistent with the available experimental data.

Interfacial and Electronic Modulation of M-Bridged Heterostructures with L-Tryptophan and Transition Metallic Oxides: Enhancing Corrosion Resistance and Photocatalytic Activity.

Despite remarkable advancements in multilayer composite materials, achieving controlled growth on stationary platforms for optimal corrosion protection and photocatalytic capabilities remains a challenge. In this study, we introduce an innovative approach by integrating bifunctional metal-organic frameworks (MOFs) into plasma-electrolyzed layers made on AZ31 Mg alloy. Metallic oxides of Zr, Ti, and W serve as new pivotal centers for MOF formation, while L-tryptophan (Trp) acts as an organic linker. This innovative approach establishes an efficient electron transport system that acts as a functional pathway for creating highly effective and versatile materials. The tunable structure of the MOF/plasma electrolyzed layer enables it to concurrently display electrochemical stability and photocatalytic activity for the photodegradation of organic pollutants. Remarkably, the WOF complex emerges as a standout performer, effectively shielding the substrate from corrosive anion attacks. This sample showcases exceptional photocatalytic efficiency of 99.61% for crystal violet solution, with sustained performance after five cycles and a 72 h corrosion test (96.55% and 98.39% degradation, respectively). Moreover, DFT calculations elucidate the fundamental bonding modes between MOFs and inorganic constituents, delivering comprehensive insights into their structural formation. Our research addresses the critical challenge of achieving controlled growth for enhanced corrosion resistance and photocatalytic activity, demonstrating a novel pathway for creating multifunctional materials with practical applications across various fields.

Ultrashort pulse ablation of printed circuit board materials using a Bessel beam

In times of digitalization, multilayer composite materials became central components in an increasing number of application fields. Thus, there is a need for optimization of the cost-intensive and time-consuming processing of multilayer composites. In this contribution, an ultrashort pulse laser-based method is presented for precise and flexible ablation of a printed circuit board base material. Therefore, an 800 nm Gaussian laser beam was transformed into a Bessel beam by an axicon to get a small spot size and an ablation result with a high aspect ratio. The influence of the average laser power, the number of exposure cycles, and the pulse duration on the geometry as well as the surface quality of ablated structures was investigated and compared to Gaussian beam ablation. Furthermore, it is shown that the results can be transferred to microdrilling processes. With the presented method, it was possible to ablate the copper top layer of the printed circuit boards as well as the FR4 layer below with a precisely adjustable depth.

Atomic layer deposition of magnetic thin films: Basic processes, engineering efforts, and road forward

Atomic layer deposition (ALD) is known as a key enabler of the continuous advances in device engineering for microelectronics. For instance, the state-of-the-art transistor technology depends entirely on ALD-grown high-κ materials. Another application branch where ALD could potentially play a similar important role in future is the magnetic thin film devices. Spin-based devices based on high-quality magnetic thin films are anticipated to provide high-efficiency operations with low power consumption. The strict quality demands the magnetic thin films must fulfill in the next-generation applications form the strong bases for the efforts to implement ALD in this application area. In this first comprehensive review on the topic, our aim is to provide an insightful account of the ALD processes so far developed for magnetic materials and to highlight the application-relevant magnetic properties of the thus fabricated thin films. Moreover, we discuss the various innovative engineering efforts made toward different multi-layered and nanostructured composite materials and complex architectures uniquely enabled by the sophisticated self-terminated film-growth mechanism of ALD. The review is finished with a brief outlook toward the future prospects and challenges in the field.

Linear Analysis of Thin-Walled Composite Profiles Weakened by Holes

Abstract The paper presents the results of the numerical analysis of the stability of C-section profiles together with the determination of the influence of the geometrical parameters of the holes and their arrangement on the strength properties of the profile, made of multilayer composite materials in a symmetrical arrangement of layers, which is deformed under the influence of the compressive force. Numerical calculations were carried out in the linear range (solution of the eigenvalue problem - critical state) using the finite element method (FEM) using the ABAQUS calculation package. Based on the obtained results, it was possible to determine the influence of the type and number of holes, their arrangement and geometric dimensions on the values of critical loads as well as the buckling modes of the profiles.

Permanent Deformation Evaluation and Instability Prediction of Semi-rigid Pavement Structure Using Accelerated Pavement Testing and Finite Element Method

Abstract A rutting prediction method for semi-rigid pavement structures using accelerated loading tests and finite element analysis was proposed in this study. Firstly, dynamic modulus and creep tests of three pavement materials were performed by changing sizes and temperatures. The prediction equation was obtained and verified using the falling weight deflectometer test and back-calculation modulus, and it was coupled into a modified Burgers model for rutting simulation for full-scale pavement structures. Results showed that the dynamic modulus of pavement materials increased with increasing specimen sizes and decreased with increasing temperature. SUP-25 had an enormous fatigue damage value (0.419) after 5,400 times repeated loading. The error between the rutting simulation and test results was 2.87 %, indicating that the model effectively applies to multilayer composite materials. Rutting deformation at one million loading times in summer was 4.6 times that in winter. From 22 to 120 km/h, rutting deformation decreased by 72.6 %. Axle load increased by 100 %, and rutting depth increased by 46.9 %, indicating that vehicle overload should be restricted, especially in low-speed sections in high-temperature areas. Rutting deformation entered the accelerated accumulation stage when the cumulative action times were more than 25 million, which requires timely maintenance and repair of pavement structures.

A novel algorithm to determine the input energy for soliton generation in a media with a patterned property

Estimation of input pulse or beam energy is crucial for soliton generation. It is rather easier for conventional solitons that are generated in isotropic media but difficult for anisotropic media, wherein a certain property of the media follows a pattern. This article presents a novel algorithm that can estimate and optimize the initial pulse energy to ensure a stable optical soliton in an anisotropic medium having a patterned property. For demonstration, local nonlinear media with periodic dispersion, diffraction, and nonlinearity as well as nonlocal nonlinear media with periodic diffraction are considered separately. This algorithm can be applied to media with any kind of dispersion map, including an irregular one. It can also be used for media with patterned diffraction, patterned nonlinearity, and multi-layered composite materials.

Energy, Exergy Investigation of Absorber Multilayered Composites Materials of a Solar Still in Algeria

Abstract The supply of drinking water has become a major challenge, despite large but relatively polluted quantities of groundwater, especially in southeastern Algeria. The use of solar energy for water desalination has become the subject of many local and global researchers. To solve this problem, we carried out an experimental study on two solar stills with a single slope. One was provided by a new absorber designed with multilayer composite materials and the other still was taken as a reference or control. The dimensions of the solar still was 0.5 × 0.5 m and the thickness of the layer of water used was 0.01 m. The results obtained show that the quantity of fresh water produced from the modified solar still was 4,312 l/m2 per day, while that of the reference solar still was 4,488 l/m2 per day, showing a difference in productivity of 3 %.

Delamination Localization in Multilayered CFRP Panel Based on Reconstruction of Guided Wave Modes

Multi-layered composite materials are being used in various engineering fields, such as aerospace, automobile, and wind energy, because of their superior material properties. Due to various impact loads during the service life of composite structures, different types of defects can occur, such as matrix cracking, fiber breakage, delaminations, etc. In this research, a novel SHM technique for delamination detection and localization using a minimum number of sensors is proposed. The analytical, numerical, and experimental analysis of GW was performed to increase the probability of detection and localization of delaminations in CFRP material. A new analytical model was developed, which enables identifying converted and transmitted modes in the presence of multiple GW modes. A 2D FFT-based spatial filtering was used to filter the GW modes. The dominant A0 mode was separated to inspect the delamination. Phase velocity is one of the important features in GW inspection to localize the delamination. A phase spectrum approach was developed to reconstruct the phase velocity dispersion of the GW modes in case material properties are unknown.

Mechanical analysis of multilayer composite materials with duroplastic matrix after exposure to low temperatures

Cryogenic engineering is gaining more and more interest in various industry sectors, which leads to an intensive search for effective solutions. The article presents the findings of mechanical testing conducted on glass-epoxy laminates at room temperature and after long-term contact with liquid nitrogen.To compare the impact properties and flexural strength, the samples were tested under cryogenic and room conditions, and then the fracture locations were identified using the Leica DVM6 microscope. The study brings value to the emerging field of cryogenic engineering by providing valuable information on the mechanical properties of glass-epoxy composites under cryogenic conditions.It has been found out that immersing the glass-epoxy composites into the Dewar had minimal influence on impact and flexural strength properties. The most noticeable changes were observed in the case of the EP_4_2 composite. The material consists of a solution of brominated epoxy resin in an organic solvent. It is used to produce laminates in electrical engineering and printed circuits in electronics, where it should exhibit excellent impact properties.One of the prospective research directions is a thorough analysis of the mechanical properties of the developed composite materials during cryogenic cycles.The study aims to determine the effect of different compositions of glass fabric-reinforced resin with a weight of 205 g/m2 on the mechanical properties of the developed composite materials at both room temperature and after long-term exposure to liquid nitrogen. Those investigations serve as surveillance for developing of new material solutions directed towards cryogenic applications and are essential for subsequent stages of research.

An investigation on gamma-ray and neutron attenuation properties of multi-layered Al/B4C composite

Nowadays, the concept of multi-layered composite materials is attracting the researchers in terms of enhancing the capabilities of shielding materials as well as extending the scope of utilization towards space sciences and cosmic radiation application. In this study, we report the manufacturing, design, and experimental investigation on newly developed multi-layered Al/B4C shielding composites. Al powder material with a purity of 99% and an average size of 15 µm is used as matrix material. Next, B4C powders with an average size of 9 µm are incorporated into the matrix as reinforcement material. Accordingly, we manufactured several different multilayer Al-B4C shield samples of 3 cm diameter and 1 cm height through powder metallurgy method. Gamma-ray transmission properties are determined using 3 × 3 NaI(Tl) scintillation detector through 60Co and 137Cs point isotropic radioisotopes. Moreover, MCNPX (version 2.7.0) is utilized for deposited energy amount and transmission factor calculations for gamma and neutron radiation. Our results showed that geometric configuration plays a crucial role in shielding efficiency of multi-layered materials. Among the manufactured samples, B4C-Al-B4C sample is reported with promising shielding properties against gamma-ray and neutron radiation. A direct relationship between the overall transmission factor values and deposited energy amount (MeV/g) in each sample is also explored for multi-layered composite shields.It was also seen that combination of layers made significantly improvement of radiation shielding properties of materials.

Investigation of the performance of the structure and energy absorption in sandwich panels of PLA/TPU manufactured by the FFF technique

Sandwich structures are often used in the automotive, marine, aerospace, and many other industrial sectors due to their desirable performance properties, energy absorption, and ability to reduce the weight of parts. Multilayer composite materials also provide various design possibilities, making it simple for producers to fabricate intricate parts. One of the most popular additive manufacturing technologies for producing complicated objects is fused filament fabrication (FFF). In this study, sandwich samples with a dual-core of polylactic acid (PLA) and thermoplastic polyurethane (TPU) were fabricated by FFF technique in three different configurations, including cylindrical, honeycomb, and tetrahedral truss cells. Their properties were determined and investigated through tensile, three-point bending, Izod impact, microhardness tests, and scanning electron microscopy. The results were compared with samples manufactured with monolithic PLA. The results demonstrated that sandwich structures with TPU cores had a high-energy absorption capability. In comparison to monolithic PLA samples, these materials’ ultimate elongation and impact strength were dramatically enhanced. However, TPU cores had lower flexural and tensile strengths than samples with PLA cores. The structure's shape significantly influences both its strength and energy absorption characteristics. Firstly, tetrahedral truss core samples revealed that the samples’ elongation climbed considerably and exceeded three times with the deposition of TPU as the inner core compared to monolithic PLA. Last but not least, in flexural testing, sandwich panels with honeycomb manufactured of PLA/TPU showed the ultimate strain unit to be about 0.08, twice as much as samples made of monolithic PLA. The lowest impact resistance and the amount of energy absorbed before collapsing were demonstrated by monolithic PLA with a honeycomb inner core. Regarding energy absorption, dual sandwich panels with PLA/TPU, including cylindrical and tetrahedral truss cores, showed the best results.