Properties Of Composite Materials Research Articles

Utilizing a multi‐layer structure to regulate the thermal conductivity of an advanced BN + EP composite insulation material: Effects of content, number of layers, and curing temperature on composites

AbstractBy blending materials such as boron nitride nanosheets (BNNSs), S‐BN and EP, hot pressing is used to realize the layered distribution of BNNSs and S‐BN fillers in the composite material, thereby forming a composite material with a sandwich structure, a horizontal and vertical heat conduction network, and improving performance of composite materials. In this paper, in order to explore the regulation of the influence of the change of objective factor variables on the thermal conductivity and electrical insulation properties of composite materials, BNNSs and S‐BN are used as the thermally conductive fillers of each layer, and EP is used as the matrix to realize the preparation of multilayer composites by high temperature and hot pressing. By changing the content of S‐BN filler in the middle layer, the number of layers of the composite material and the curing temperature of the composite material, the effects of the changes of the three objective factors on the microstructure, thermal conductivity, variable temperature conductance, dielectric, breakdown, DSC and infrared thermal imaging of composite materials are explored respectively. The results show that the multilayer structure ensures good bonding. As the content, number of layers and curing temperature increase, the thermal conductivity gradually raises to 2.64 W/(m·K), which is also proved by DSC and infrared thermal imaging. Composite materials also ensure considerable breakdown strength, control the preparation cost, reduce the preparation difficulty and expand the practicability of thermal insulation materials in the thermal conductivity field.Highlights Form a composite material with a sandwich structure, a horizontal and vertical heat conduction network. By changing three objective factors on the microstructure, Properties of composite materials are explored respectively. The thermal conductivity gradually raises to 2.64 W/(m·K). Composite materials also ensure considerable breakdown strength (insulation), control the preparation cost. Expand the practicability of thermal insulation materials in the thermal conductivity field.

Determination of the shear characteristics of polymer composite materials

Layered polymer composite materials (LPCM) based on carbon fiber and epoxy are widely used in the construction of commercial aircraft both in manufacturing lightly loaded and main power elements of aircraft airframes. The level of mechanical characteristics for all the composite constructions must be confirmed by experimental data of coupon testing. One of the most important characteristics of a layered composite material is the ability to perceive shear loads. Standard test methods ASTM D5379 and ASTM D7078 are used to determine the shear characteristics. These test methods enable determination of the shear properties of composite materials based on a polymer matrix reinforced with a high-modulus fiber. Comparative tests were carried out according to both methods. The samples were made from the wall and the tehnological zones of the spar to determine the values of destructive stresses and shear modulus. The results showed that the shear stresses in the material obtained by ASTMD7078 significantly (1.8 times) exceed those determined by ASTM D5379. At the same time, the modulus of elasticity differs slightly (by 1.1 times). This is due to the sensitivity of the test results to the method of loading and the quality of the specimens. When stretched according to ASTMD7078, the load is transmitted through the front surfaces of the coupons, which are obtained with sufficiently high quality from the tooling or vacuum bag. When compressed by ASTM D5379, the parallelism of the faces through which the load is distributed becomes critical. Moreover, the thickness of the sample also affected the test results obtained according to ASTM D5379, the greater the thickness, the greater the shear modulus. Proceeding from the results obtained, the recommendations on the choice of the method to be used for determining the shear characteristics of LPCM are formulated.

Circular inclusion with a refined linearized version of Steigmann–Ogden model

The plane deformation of an infinite elastic matrix enclosing a single circular inclusion incorporating stretching and bending resistance for the inclusion–matrix interface is revisited using a refined linearized version of the Steigmann–Ogden model. This refined version of the Steigmann–Ogden model differs from other linearized counterparts in the literature mainly in that the tangential force of the interface defined in this version depends not only on the stretch of the interface but also on the bending moment and initial curvature of the interface (the corresponding bending moment relies on the change in the real curvature of the interface during deformation). Closed-form results are derived for the full elastic field in inclusion–matrix structure induced by an arbitrary uniform in-plane far-field loading. It is identified that with this refined version of the Steigmann–Ogden model a uniform stress distribution could be achieved inside the inclusion for any non-hydrostatic far-field loading when R = 3 χ int / λ int (where R is the radius of the inclusion, while λ int and χ int are the stretching and bending stiffness of the interface). Explicit expressions are also obtained for the effective transverse properties of composite materials containing a large number of unidirectional circular cylindrical inclusions using, respectively, the dilute and Mori–Tanaka homogenization methods. Numerical examples are presented to illustrate the differences between the refined version and two typical counterparts of the Steigmann–Ogden model in evaluating the stress field around a circular nanosized inclusion and the effective properties of the corresponding homogenized composites.

The influence of spark plasma sintering on multiscale mechanical properties of nickel-based composite materials

The paper presents a comprehensive investigation of the influence of the main process parameters of spark plasma sintering on the mechanical and microstructural properties of nickel-silicon carbide composites at various scales. Microstructure analysis performed by scanning and transmission electron microscopy revealed a significant interfacial reaction between nickel and silicon carbide due to the decomposition of silicon carbide. The chemical interaction of the matrix and reinforcement results in the formation of a multicomponent interphase zone formed by silicides (Ni31Si12 or/and Ni3Si) and graphite precipitates. Furthermore, several types of structure defects were observed (mainly nano/micropores at the phase boundaries). These significantly influenced the mechanical response of nickel-silicon carbide composites at different levels. At the macroscopic scale, uniaxial tensile tests confirmed that applying a 1000 °C sintering temperature ensured that the manufactured composite was characterised by satisfactory tensile strength, however, with a considerable reduction of material elongation compared to pure nickel. Moreover, the fractography study allowed us to identify a significant difference in the damage mode for certain nickel-silicon carbide samples. Secondly, the interface of the nickel matrix and silicate interphase was tested by bending with microcantilevers to evaluate its deformation behaviour, strength, and fracture characteristics. It was confirmed that a diffusive kind of interface, such as Ni-NiSi, demonstrates unexpected bonding properties with a relatively large range of plastic deformation. Finally, the nanoindentation of three main components of the nickel-silicon carbide composite was executed to evaluate the evolution of nanohardness, Young's modulus, and elastic recovery due to the application of various spark plasma sintering conditions.

Exploring elastic properties of fly ash recycled aggregate concrete: Insights from multiscale modeling and machine learning

The primary focus of this study is to analyze the impact of different components of fly ash recycled aggregate concrete (FARAC) on its elastic properties, aiming to suggest it as a potential alternative to traditional concrete. For this study, a variety of techniques were employed, such as multiscale modeling, finite element methods, and Mori-Tanaka theory. The study employed supervised machine learning methods to conduct classification and regression analyses, with the goal of investigating the impact of mix proportion on elastic properties. The results obtained from the machine learning models suggest that the XGBoost and K-Nearest Neighbors algorithms have shown exceptional precision when compared to the other algorithms, achieving an accuracy of over 0.9. The current investigation reveals that the elastic characteristics of FARAC are primarily affected by fly ash and calcium silicate hydrate (C-S-H) in comparison to other components. According to the research findings, incorporating recycled aggregate content in the range of 0–100% resulted in a 25% decrease in Young's modulus and an 8% increase in Poisson's ratio of FARAC. In addition, two web-based applications have been developed to calculate the elastic properties of composite materials with spherical inclusions using the Mori-Tanaka theory, and to predict the elastic properties of FARAC through machine learning.

ИССЛЕДОВАНИЕ ТРИБОТЕХНИЧЕСКИХ СВОЙСТВ КОМПОЗИЦИОННОГО МАТЕРИАЛА НА ОСНОВЕ АЛЮМИНИЕВОЙ МАТРИЦЫ АРМИРОВАННЫЙ СТАЛЬЮ ИЛИ БАЗАЛЬТОМ

The study objective is to evaluate the tribo-engineering properties of composite materials based on an aluminum matrix reinforced with steel or basalt in comparison with a material without reinforcement, and to develop a technology for obtaining such composite materials. Frames consisting of multidirectional fibers were used as reinforcing components: basalt wool (175-200 kg/m3 density); steel wool (4# class); melting temperatures of steel and basalt, which make up steel and basalt wool, are above 10000C, which makes it possible to pour aluminum without changing the aggregate state of reinforcing frames. The percentage of reinforcing components by weight is 4-5%. Deformable AB aluminum alloy was used as a matrix, which differs from the alloys of Al-Mg-Si system because of its higher level of tensile and yield strength. The composite materials under study were obtained by the liquid–phase method - casting according to melting models. Tribo-engineering properties were tested on a friction machine in the medium of Lukoil standard 10W40 SF/CC engine oil. To determine the anti-wear properties, tests were carried out for 1 hour, and to determine the antisize properties and the seizure load, tests were carried out with a constant increase in the load on the friction unit. The assessment of anti-wear and antisize properties was carried out by comparing the values of wear spots and seizure loads. It is found that the anti-wear properties increase by 76-85% when reinforcing samples with basalt wool and by 46-76% when reinforcing with steel wool in relation to an unreinforced sample. Antisize properties increase with basalt reinforcement by 23%, and decrease by 7% with steel reinforcement. Studies on assessing tribo-engineering properties of samples obtained by casting from AB aluminum alloy reinforced with basalt and steel have shown an improvement in anti-wear and antisize properties in relation to samples from AB alloy without reinforcement.

Effects of average number of platelets through the thickness and platelet width on the mechanical properties of discontinuous fiber composites

In this study, we experimentally and numerically investigate the evolution of the tensile material properties of Discontinuous Fiber Composites (DFCs) with an increasing average number of platelets through the thickness for two different platelet widths.The results show that both the number of platelets and the platelet width have significant effects on the tensile modulus and strength. We find that not only the average mechanical properties but also their coefficients of variation change according to the different DFC mesostructures.To understand the relationship between material morphology at the mesoscale and corresponding material properties, we developed a random platelet mesostructure generation algorithm combined with explicit finite element models. Leveraging the computational tools, we find that moduli and strength increase with increasing average number of platelets through the thickness. The increasing trend continues until reaching an asymptotic limit at about 45 layers through the thickness for the narrow and 27 layers for the square platelets.In the study, we address the importance of having accurate simulations of the mesostructure to match not only the average modulus and strength but also their associated coefficients of variation. We show that it is possible to accurately predict the tensile material properties of DFCs, including their B-basis design values. This is a quintessential condition for the adoption of DFCs in structural applications.

Effect of adding (ZrO2-ZnO) nanopowder on the polymer blend (lamination and methyl vinyl silicone) in a hybrid nanocomposite material

A polymeric blend combines two or more polymers to form a new material with different physical properties. In this work, a base material consisting of a polymeric mixture was manufactured to improve its properties and then strengthened with nanoparticles (ZrO2-ZnO) to develop a hybrid nanocomposite material, which has better properties than its constituent materials. Reinforcement material, i.e., (ZrO2-ZnO) nanoparticles, were prepared using relaxation method. A polymeric resin mixture (lamination and methyl vinyl silicone) was prepared by adding methyl vinyl silicone to the lamination resin in different ratios (4 %, 8 %, 12 %, and 16 %). The mixture properties were studied through tensile, bending, shock, and hardness tests, and the optimal results were achieved for the 12 % ratio. The resulting composite nanoparticles and their properties were studied using EDX, X-Ray, SEM, and PSA techniques. Finally, the nano-hybrid composite material was manufactured by choosing the optimal blend (i.e., 12 %). It had the highest polymeric base material properties, and nanoparticles were added at different dosages (3 %, 6 %, 9 %, and 12 %). The resulting hybrid composite material properties were studied through different tests (tensile, flexural, impact, and hardness). The results showed that the binary composite nanoparticles improved the properties of the mixture for both sizes (30 nm and 89 nm) at all mixing ratios, compared to the control specimens (i.e., without any addition). The optimal results were obtained when 30 nm particles were added and for all tests compared to samples reinforced with 89 nm particles. The optimal ratio of (ZrO2-ZnO) was 9 % wt 30 nm size, representing the best sample in terms of the resulting properties. It is recommended to use the sample with the 9 % addition of (ZrO2 - ZnO) wt with a granular size of (30 nm) in essential applications, including prosthetics (foot).

An embedded digital element model to simulate the wrinkle defects driven by the consolidation of composites

Understanding the mechanisms of fiber wrinkling during the compaction process is of paramount importance as fiber wrinkling significantly affects the mechanical properties of composite materials. This study introduces an embedded digital element model for simulating the consolidation process of prepreg. Flexible digital element chains are employed to simulate the reinforcing effect of fibers on resin, accounting for the viscoelastic constitutive behavior of uncured resin. The simulation captures intra-layer wrinkles and in-plane waviness defects in the consolidated prepreg, thereby uncovering the mechanism behind fiber wrinkle formation during composite material prepreg consolidation. The accuracy of the model is validated through compression experiments on flat plates and L-shaped structures. The results demonstrate that the proposed embedded digital element model accurately predicts wrinkle defects. Factors such as interlayer friction of the prepreg, consolidation temperature, and mold curvature radius significantly influence the shape and size of wrinkles.

Transfer-learning-based strategy for enhancing prediction accuracy and computational efficiency of nonlinear mechanical properties in composite materials

In modern composite design, superior macroscopic mechanical properties can be achieved by optimizing the microstructures of materials. However, the direct prediction of the microstructure–property relationship under nonlinear conditions through numerical methods can be inefficient or imprecise. In this study, a transfer learning strategy based on the reduced order model (ROM) was proposed, offering an enhanced and rapid prediction of the mechanical responses of composite materials under nonlinear conditions. Initially, an extensive training dataset was generated by applying the ROM, used to pre-train the neural network model. Following this, a few data calculated from full-order finite element models were leveraged to fine-tune the network parameters. This approach exploits the efficient data generation capability of the ROM, with its potential computational inaccuracies in nonlinear scenarios mitigated, leading to an improvement in the accuracy and efficiency of the surrogate model. Numerical examples of a nonlinear hyper-elastic material with inclusions were examined, revealing that the computational cost in the offline stage of the transfer learning method is only half that of traditional neural network models, and it enable near real-time predictions in the online stage. Notably, it was shown that the accuracy loss of the developed surrogate model in scenarios of strong non-linearity is significantly less than that of the ROM. This method presents an innovative pathway for the swift and accurate evaluation of the effective mechanical properties of composite structures, with the potential to offer valuable insights for related methodological research.

APPLICATION OF CARBON-CARBON COMPOSITE MATERIALS FOR THE MANUFACTURE OF HIGH-TEMPERATURE HEATERS OF HEAT EXCHANGERS WITH AUTOMATIC TEMPERATURE CONTROL


 The article justifies the use of high-temperature heaters made of carbon-carbon composite material (CCCM) for the thermal unit of a silicon single crystal growth chamber. The conducted analysis confirms that the electrical properties of composite materials, specifically their specific resistance, allow for the creation of heating elements for high-temperature vacuum furnaces or furnaces operating in inert atmospheres at temperatures up to 2200°C.
 The use of heaters made from carbon-carbon composite material eliminates the main drawback of graphite heaters - uncontrolled energy dissipation during resistive heating due to the presence of transient electrical resistance at the junctions of graphite plates, and ensures a more uniform temperature field throughout the chamber volume. The capabilities in terms of the maximum permissible temperature of such a CCCM heater exceed the working temperature by more than two times, which also positively affects the service life.
 The modes of thermal processes occurring during crystal growth are determined by the technological process depending on the composition of the raw material and require high uniformity of heating in the working zone, high precision, and stability of the heater's temperature control. For precise temperature regulation, it is proposed to additionally measure the integral temperature in the chamber indirectly, which is based on measuring the electrical current passing through the heater, which is in thermodynamic equilibrium with the object. Thus, the heater is considered as a system susceptible to various thermal influences that determine the heat transfer process and the temperature change within the chamber and in the zone of the thermal unit's bricks.
 An improved structural diagram of a step-type extremal control system is proposed for automatic temperature control of a high-temperature heater using modern power electronics, sensors, microprocessors. To ensure speed and accuracy in temperature control, the pulse-phase control method implemented with modern specialized thermoregulator with PID-regulation was applied.
 Experimental tests conducted on the «Redmet-30» installation under factory conditions confirm the energy efficiency of using high-temperature heaters made of CCCM.

Mechanical, physical and thermal properties of composite materials produced with the basidiomycete Fomes fomentarius

BackgroundTo achieve climate neutrality, fundamentally new concepts of circularity need to be implemented by the building sector as it contributes to 40% of anthropogenic CO2 emission. Fungal biotechnology can make a significant contribution here and help eliminate fossil dependency for building material production. Recently, we have shown that the medicinal polypore Fomes fomentarius feeds well on renewable lignocellulosic biomass and produces composite materials that could potentially replace fossil fuel-based expanded polystyrene as insulation material.ResultsIn this study, we explored the mechanical, physical, and thermal properties of F. fomentarius-based composite materials in more detail and determined key performance parameters that are important to evaluate the usability of F. fomentarius-based composite materials in the construction sector. These parameters were determined according to European standards and included compressive strength, modulus of elasticity, thermal conductivity, water vapour permeability, and flammability of uncompressed composites as well as flexural strength, transverse tensile strength, and water absorption capacity of heat-pressed composites, among others. We could show that uncompressed composites obtained from F. fomentarius and hemp shives display a thermal conductivity of 0.044 W (m K)−1 which is in the range of natural organic fibres. A water vapour permeability of 1.72 and classification into flammability class B1 clearly surpasses fossil-based insulation materials including expanded polystyrene and polyurethane. We could furthermore show that heat-pressing can be used to reliably generate stiff and firm particleboards that have the potential to replace current wood-based particleboards that contain synthetic additives. X-ray microcomputed tomography finally visualized for the first time the growth of hyphae of F. fomentarius on and into the hemp shive substrates and generated high-resolution images of the microstructure of F. fomentarius-based composites.ConclusionThis study demonstrates that fungal-based composites produced with F. fomentarius partially meet or even exceed key performance parameters of currently used fossil fuel-based insulation materials and can also be used to replace particleboards.

Effect of Varying Graphite Concentration on Electrodynamic Properties of AlN-Based Composite Materials

Effect of Varying Graphite Concentration on Electrodynamic Properties of AlN-Based Composite Materials

A Critical Review on Tribological and Mechanical Characteristics of Hybrid Polymer Composite Materials

AbstractThis review paper presents tribological and mechanical characteristics of hybrid polymer composite materials that exhibit low friction and low wear. Polymer fiber reinforced materials possess low weight and high specific quality along with high specific stiffness. This study targets a critical review of wear and frictional characteristics of hybrid polymer composite materials. Tribological properties have been evaluated by various researchers using a rotating pin‐on‐disc tribometer and reciprocating wear testing machine. Most likely filler materials are carbon, graphite, nano silica, bronze, glass fibers, MoS2, and polytetrafluoroethylene (PTFE) added in the polyether ether ketone (PEEK), polyamide 66, thermoses polymer, etc. It improves mechanical and tribological properties of hybrid composite materials. This review paper aims to highlights the comparative study of various fillers added in PEEK, Polyamide 66, and thermoses polymer hybrid materials. Recently hybrid composites are used in wide range of applications since it has light weight and high strength.

Cross-linking gradient model in disperse systems

The article presents the research results of the disperse systems cross-linking process containing solid and liquid phase bases on the continuum mechanics apparatus use within the incompressible fluid model framework. The system formation schemes of interfacial layers in fine clearances between solid particles with wall-adjacent zones formation, in which conditions of liquid and solid phase interphase contact are provided, and the cores with constant interphase pressure are considered. The authors have obtained expressions for the values of wedging pressure depending on the thickness of the interfacial layers overlapping area, which determine the interfacial contacts strengthening degree. The dependences given in the paper are a theoretical basis for a new approach to modelling surface phenomena from the position of continuum mechanics equilibrium. The facilitating mechanism of the wedging pressure long-range action outside the interfacial layers system area is given. The authors present the modelling results of a single liquid-solid interphase layer bounded, on the one side, by a solid surface and, on the other side, by a volume liquid phase and the results of modelling the effects of structuring disperse systems based on the liquid interphase layer study formed in the clearance between solid surfaces. Under certain conditions in such systems the effect of structuring, leading to a sharp increase in the strength properties of disperse-filled composite materials, which is the basis of modern nanotechnology concepts, is manifested. The dualism of the liquid phase, consisting in the ability to exhibit the properties of both liquid and solid body, is shown. It is proved that the main disperse systems structure formation factor is the formation of interphase stresses powerful gradients at the thickness of interphase layers.

Prediction of Electrophysical Properties of Organic-Inorganic Composite Materials

Prediction of Electrophysical Properties of Organic-Inorganic Composite Materials

Luminescent Properties of Composite Materials Based on Porous Glasses Activated by Silver and Lanthanum

Luminescent Properties of Composite Materials Based on Porous Glasses Activated by Silver and Lanthanum

Preliminary study of Acoustic Black Holes implemented in CT/MRI housings including validation experiments

An increasing number of interventional use of computer tomograph (CT) scanners and magnetic resonance tomographs (MRI) leads to the need for particularly quiet medical imaging in order to minimize the stress level for patients as well as medical staff. Due to the many different imaging sequences, noise reduction measures have to consider a wide range of different frequencies. Especially the use of Acoustic Black Holes (ABHs) seems to be a promising strategy to reduce vibration-induced noise. The objective of this study is to extend conventional measures for minimizing structural vibrations, usually realized by applying composite stiffeners, by adding ABHs directly into these stiffening components. This allows vibration maxima to be minimised efficiently. In the first step, the vibroacoustic properties of composite materials are investigated numerically and the created simulation model is validated by experiments. Based on these results, the influence of stiffeners on the structural behaviour is investigated and an optimised design for minimum surface velocities is found. To further reduce surface velocities in the frequency range where the human ear is particularly sensitive, ABHs are tested. In this context it is investigated whether ABHs can be advantageously combined with conventional stiffeners. Keywords: Medical devices, Acoustic black holes, Noise and vibration

Prediction on the wear rate of epoxy composites reinforced micro-filler of the natural material residue using Taguchi – neural network

The abrasive wear rate of epoxy composites reinforced with fillers sourced from recycled natural waste consisting of pollen of palm (PPW) and seashells (SSW) was studied.
 Due to the importance of polymer composites used in the tribological couplings of machinery structures, as well as their possible use in brake pads as alternative materials for harmful components in environmentally polluted asbestos, the current research seeks to develop the tribological properties of composite materials reinforced with natural fillers and environmentally friendly. The research investigated the effect of two factors, the weight percentage of natural filler wt. % (0.5 %,1 %, and 1.5 %) and testing loads (1000 g, 2000 g, 3000 g) upon the wear resistance of epoxy composites. The importance of developing epoxy compounds is evident, especially since their work does not require lubricating conditions in various industrial fields, and therefore the development of their bonding properties will increase their operational life and achieve economic benefit for the industrial sector and the environment at the same time. The epoxy composites were subjected to abrasive wear tests under dry friction conditions using a pin-on-disc system. Signal-to-noise (S/N) analysis is adopted to study the influence of the two factors, wt. % and test loads, upon the tribological wear resistance of epoxy composites. A predictive model depending on the regression equation was developed to predict the wear resistance of epoxy composites. The results showed an improvement in the wear resistance of the composite material compared to the epoxy sample without filling by about 47 %. The optimum condition for wear resistance of epoxy composites has been achieved with a weight ratio of (1.5 %) and an applied load of 1000 g

Interfacial nanolayer effect on thermophysical properties of silica-paraffin phase change material - A molecular dynamics simulation

Thermophysical properties of composite phase change materials (PCMs) are influenced by the interfacial nanolayer. Molecular dynamics (MD) method is used to study the effect of interfacial nanolayer on thermophysical properties of silica-paraffin composite PCM. The simulation results show that the melting enthalpy is reduced from 197.9 J·g−1 to 29.1 J·g−1, and the thermal conductivity is enhanced from 0.142 W·m−1·K−1 to 0.268 W·m−1·K−1, when the silica thickness is increased from 0 to 15.0 Å. The interfacial nanolayer is observed in composite PCM, and its thickness increases with the increase of silica wall thickness. In the composite PCM with 7.0 Å silica wall, a loss of 62.9% in the melting enthalpy is observed, with 32.6% attributed to the silica mass and 30.3% attributed to the nanolayer. Based on that, a modified model is proposed to predict the melting enthalpy of composite PCMs by considering the effects of both silica mass fraction and nanolayer. To reveal the thermal conductivity enhancement mechanism, the total heat flux is decomposed into three terms (namely, kinetic energy term, potential energy term and interaction energy term). It is found that the interaction energy term has the largest contribution to the total heat flux. The presence of nanolayer strengths the interactions, leading to the thermal conductivity enhancement.