Showing papers in "Functional composites and structures in 2023"
TL;DR: In this paper , a review of published literature that discusses the utilization of biochar (BC) and plastics as filler and matrix, respectively, in a composite material is presented, and the drawbacks and potential associated with the development of BFPCs are discussed.
Abstract: This study is a review of published literature that discusses the utilization of biochar (BC) and plastics as filler and matrix, respectively, in a composite material. These composites, referred to as Biochar-filled plastic composites (BFPCs), play a significant role in the production of environmentally friendly materials. This paper provides an overview of BFPCs, their properties (mechanical, rheological, morphological, electrical, and thermal properties), fabrication techniques, and prospects and challenges associated with their development. Even though there have been previous studies on BFPCs, none of these studies have discussed the drawbacks and potential associated with the development of BFPCs. BCs’ small weight makes them a more appealing option than traditional mineral fillers when it comes to reducing vehicle weight. Due to their superior mechanical and thermal qualities, as well as their low carbon footprint, BC-filled plastic composites (BFPCs) play a significant role in the production of environmentally friendly materials. It was observed that either melt extrusion or injection molding are usually used to fabricate BFPC. It was observed that the properties of BFPCs are influenced by several factors such as the type and concentration of plastic, method of fabrication, the BC content, mixing uniformity of the mixture, wetting, and particle dispersion. Challenges of BFPCs were also discussed, such as the issue of particle agglomeration and poor interfacial bonding at high BC concentrations in the composite. Composites made from recycled polymers or biodegradable polymers can be developed to improve the composites’ overall sustainability.
2 citations
TL;DR: In this paper, several structural parameters, reinforcement conditions, and chemical treatments have been investigated to reveal their effects on the final desired mechanical performance of lignocellulosic corn/polyester composites for sustainable green products.
Abstract: Facilitating finding low-cost renewable and sustainable environmental functional alternative materials for green products has been recently emphasized. Lignocellulosic materials are of such potential alternatives to enhance the modern cleaner production theme. In this work, several structural parameters, reinforcement conditions, and chemical treatments have been investigated to reveal their effects on the final desired mechanical performance of lignocellulosic corn/polyester composites for sustainable green products. Low-cost treatment solutions as sodium chloride, phosphoric and citric acids were considered for Mediterranean corn agro waste lignocellulosic fibers. Results have revealed that superior mechanical performance enhancements were occurred for the produced bio-composites. It was demonstrated that prepared composites were capable of enhancing the tensile strength as well as modulus for all types of treatment. About 157% tensile strength enhancement was achieved in case of 30 wt.% fiber content when treated with phosphoric and citric acids. Moreover, sodium chloride treatment was capable of achieving 81 MPa for the 20 wt.% fiber loading comparable to 54.7 MPa for the matrix. The modulus of elasticity property was also enhanced more than 600% for the untreated fibers and sodium chloride treated ones. This obviously demonstrates the potential of such low-cost fiber/low cost treatment synergy to fabricate potential green materials for sustainable industrial applications as well as enhance evaluating such materials from various technical stand points for the future sustainable cleaner production.
2 citations
TL;DR: In this paper , the authors developed soft polydimethylsiloxane (PDMS)-Ecoflex auxetic structures using a 3D printing technique, leading to high fabrication reliability and repeatability.
Abstract: Auxetic structures with negative Poisson’s ratio have received much attention due to their attractive behavioral properties in next-generation metamaterials and robotic applications. However, until now, there has been a lack of research into using soft materials to reliably develop a largely-deformable auxetic structures. Here, we develop soft polydimethylsiloxane (PDMS)-Ecoflex auxetic structures using a 3D printing technique, leading to high fabrication reliability and repeatability. Water-soluble filaments are employed to design sacrificial mold structures that quickly dissolve in warm water. By measuring the mechanical properties and light transmittance of soft composite membranes with various mixing ratios of PDMS and Ecoflex, the intrinsic characteristics of the composite membranes are determined. The newly fabricated soft auxetic structures composed of PDMS and Ecoflex composites always exhibit negative Poisson’s ratio during stretching. The negative Poisson’s ratio of the structure is maximized when PDMS and Ecoflex have a 2:1 mixing ratio and nominal strain is less than 5%. Advances in technology to reliably fabricate soft auxetic structures using 3D printers are believed to promote next-generation applications such as wearable sensors and energy-absorbing structures.
1 citations
TL;DR: In this paper , the free vibration analysis of fiber metal laminates (FMLs) is discussed, which mainly refers to dynamic analysis, macro mechanical and micro mechanical approaches, and temperature effects.
Abstract: It is a challenging target to improve the dynamic analysis and free vibration analysis of fiber metal laminates (FMLs) while providing great promise as lightweight structural components. FMLs have attracted increasing research interest in various multi-stack FML components to enlarge industrial applications. This review paper concentrates on the free vibration analysis of FMLs, which mainly refers to dynamic analysis, macro mechanical and micro mechanical approaches, and temperature effects. The available types of experimental vibration methods on FMLs are described. Moreover, dynamic analysis of FMLs is mainly reviewed in recent studies of FMLs on the macro mechanical and micromechanical scale aspects, and the temperature effect is also studied. Furthermore, several classical theoretical equations of different FMLs on free vibration analysis are summarized. In addition, optimization studies on FMLs under dynamic analysis are further discussed.
1 citations
TL;DR: In this paper , the impact of nano-SiO2 on the tensile, flexural, and compressive characteristics of the open-hole CFRP laminated composites is experimentally determined.
Abstract: Carbon fiber are of great importance materials exploited in various industrial applications in the recent years. Because of its strong flexural and compressive properties, these fibers have been commonly utilized as a reinforcement for producing polymer composite laminates. Carbon fiber-reinforced polymer (CFRP) laminates are subjected to extreme forces and damaged. In the component assembly of the structures, one of the conventional damages that still occurs on the CFRP laminates is holes that is created on the specimen by drilling tools, which causes a reduction in the laminates’ mechanical strength. One of the suggested ways to strengthen the mechanical properties of composites is to add nanoparticles. Therefore, the impact of silica nanoparticles (nano-SiO2) on the tensile, flexural, and compressive characteristics of the open-hole CFRP laminated composites is experimentally determined in this research. Nano-SiO2 with various weight percentage of 0, 1, 2, 3, and 4 is added into the CFRP. A scanning electron microscope images are used to observe the microscopic structure of the composites. The results showed that adding 1–3 wt.% of nano-SiO2 into the CFRP enhances the tensile, flexural, and compressive strength of the specimens and reduces the fiber pull out and delamination.
TL;DR: In this paper , a lap joint method was proposed to measure the ILSS of carbon or glass fiber-reinforced fabric composites (CFRC) by minimizing the discrepancy between the experiment and finite element analysis of ILSS test.
Abstract: Interlaminar shear strength (ILSS) indicates the resistance to interlaminar delamination of fiber-reinforced composite structures. The short beam shear (SBS) method has been commonly used for ILSS measurement, but unwanted failure modes can appear like a compressive or tensile failure in surface, and diagonal shear failure, causing poor measurement accuracy. The lap joint method has advantage that leading to a clear measurement of the shear strength. This paper proposed the lap joint method for extracting ILSS values of co-cured carbon or glass fiber-reinforced fabric composites (CFRC or GFRC) by minimizing the discrepancy between the experiment and finite element analysis of ILSS test. The lap joint method can compensate for the shortcomings of the SBS method. The calculated ILSS based on the lap joint method (LJ-ILSS) with correction factors showed similar values to the ILSS values by SBS method (SBS-ILSS) done by our work and other works of literature. Therefore, the proposed lap joint method has shown potential as a method to measure ILSS of the co-cured fiber-reinforced fabric composites, but also it can be extended to other types of fiber-reinforced composites.
TL;DR: In this paper , polyethylene glycol (PEG)-aided zinc oxide (ZnO) nanoparticles were synthesized by fusion of precipitation-cum-hydrothermal method.
Abstract: In this study, polyethylene glycol (PEG)-aided zinc oxide (ZnO) nanoparticles (NPs) have been synthesized by fusion of precipitation-cum-hydrothermal method. The PEG/ZnO NPs were investigated by x-ray diffraction (XRD), Fourier-transform infrared (FTIR) transformation, UV-visible field emission scanning electron microscope (FESEM), energy dispersive x-ray, high resolution transmission electron microscope (HRTEM), and RAMAN techniques. XRD analysis confirms the formation of the wurtzite phase with a crystallite size of 8 nm of synthesized PEG/ZnO. While FESEM and HRTEM investigations reveal the formation of distinct structural forms, FTIR investigations show interactions between PEG and ZnO. High crystallinity of PEG/ZnO is observed in the selected area electron diffraction pattern. The Brunauer–Emmett–Teller (BET) study revealed that ZnO NPs have a mesoporous structure with a significant specific surface area of 42 m2 g−1. The evaluation of photocatalytic activity of PEG/ZnO-based photocatalyst was carried out via the degradation of typical azo dye (industrial methylene blue (MB) dye) along with total organic carbon (TOC) analysis. The PEG-ZnO (dose 200 mg l−1) was found to be an efficient photocatalyst for the degradation of MB dye. The degradation reaction exhibits pseudo-first-order kinetics. Additionally, TOC removal was monitored, elucidating almost complete mineralization.
TL;DR: In this article , a thermally tunable broadband metamaterial absorber, with switchable functionality in the terahertz band, consisted of periodically arranged vanadium dioxide (VO2) and a gold film separated by a layer of polyimide is reported, which is capable of switching from absorber to reflector through the phase change property of VO2.
Abstract: In this paper, a thermally tunable broadband metamaterial absorber, with switchable functionality in the terahertz band, consisted of periodically arranged vanadium dioxide (VO2) and a gold film separated by a layer of polyimide is reported, which is capable of switching from absorber to reflector through the phase change property of VO2. When VO2 is in the metallic state, three near-perfect absorption peaks localized at 3.48 THz, 5.09 THz and 7.05 THz are obtained, and the combination of them gives rise to a broadband absorption, more than 90% of absolute absorption bandwidth reaches 4.35 THz (3.1–7.45 THz) with a relative absorption bandwidth of 82.46%. When VO2 is in the dielectric state, it can switch from near-perfect broadband absorption to near-perfect reflection with the maximum intensity modulation of 92.4%. The broadband absorption is insensitive to polarization of incident beam due to symmetrical structure design and exhibits excellent tolerance for large oblique incidence angle. In addition, size changes of patterned VO2 array structure provides a large impact on the absorption performance of the thermally tunable device, especially the absorption bandwidth. Our proposed device is expected to have outstanding prospects in terahertz thermal imaging, communications, and temperature-controlled metasurface.
TL;DR: In this article , a 3D printed ceramic nanocomposite with 0.1 wt% Boron nitride nanotubes (BNNTs) was prepared by fusing it at high temperatures.
Abstract: Boron nitride nanotubes (BNNTs) are the perfect candidate for nanofillers in high-temperature multifunctional ceramics due to their high thermal stability, oxidation resistance, good mechanical properties, high thermal conductivity, and radiation shielding. In this paper, 3D printed ceramic nanocomposite with 0.1 wt% of BNNT was prepared by fusing it at high temperatures. Samples were built with three different print directions to study the effect of print layers on mechanical performance along with BNNT addition. Dynamic mechanical analysis is performed to study the length effect of nanoscale reinforcements on the mechanical properties of the printed ceramic composites reporting significant improvements up to 55% in bending strength and 72% in bending modulus with just 0.1 wt% BNNT addition. A 63% thermal diffusivity improvement of ceramic by adding BNNTs is observed using laser flash analysis. The bridging and pull-out effect of nanotubes with a longer aspect ratio was observed with high-resolution microscopy. Such composites’ modeling and simulation approaches are crucial for virtual testing and industrial applications. Understanding the effect of nanoscale synthetic fillers for 3D printed high-temperature ceramics can revolutionize future extreme environment structures.
TL;DR: In this article , the design principles and fundamental parameters for bioinspired composites design are discussed, with the main challenges to be overcome in the development of bioinspired materials discussed, and the presentation of some experimental studies that lead to the practical application of such principles.
Abstract: Biomimetics enables the use of nature as a source of inspiration for the elaboration of high-performance materials. In this scenario, the development of bioinspired composites emerges as a promising proposal, capable of generating technological innovation in numerous areas of engineering, considering the exceptional mechanical performance of materials of this kind. That said, this review article characterizes the design principles and fundamental parameters for bioinspired composites design. In addition, the main challenges to be overcome in the development of bioinspired materials are discussed, with the presentation of some experimental studies that lead to the practical application of such principles. Future applications for this class of materials are also highlighted.
TL;DR: In this article , the effect of carbon nanofiber (CNF) on the buckling behavior of sandwich beams under axial compressive load was examined, and the experimental test results indicated that carbon fiber as a stiffening interface in hybrid samples improved the specific critical load compared to Innegra samples.
Abstract: This study examined the effect of carbon nanofiber (CNF) on the buckling behavior of sandwich beams under axial compressive load. Three different configurations of sandwich beams consisting of composite skins with different arrangement of layers and polyvinyl chloride (PVC) foam core were considered. Each composite skin is made of four layers reinforced with different materials consisting of Innegra, carbon and Innegra/carbon (hybrid) and epoxy resin modified by CNF. Because of the difference in the thickness of the samples, the specific critical load parameter (the ratio of the critical buckling load to the thickness of the structure) was used to compare the buckling behavior of sandwich beams. The experimental test results indicated that carbon fiber as a stiffening interface in hybrid samples improved the specific critical load compared to Innegra samples. Also, the addition of 0.3 wt%-CNF increases the specific critical load, while the further increase of CNF led to the decrease of the specific critical loads, which is the main cause of weak interfacial stress between CNF and epoxy resin. In addition, the effect of different percentages of CNF and types of fibers on the increase in toughness and damage mechanisms were investigated.
TL;DR: In this article , the crashworthiness behavior and energy absorbing characteristics of the thermoplastic polymer composite lattice cubic structures were experimentally investigated under quasi-static compression and four design patterns such as Cuboctahedron, Kelvin cell, Truncated cube in square and dividend square geometrics were considered and fabricated through fused deposition modelling (FDM) technique.
Abstract:
The unique compressive behaviour of lattice cubic structures as well as their high specific strength and significant energy absorbing characteristics makes them an attractive solution for crashworthiness applications. Hence in this research study, the crashworthiness behaviour and energy absorbing characteristics of the thermoplastic polymer composite lattice cubic structures were experimentally investigated under quasi-static compression. Four design patterns such as Cuboctahedron, Kelvin cell, Truncated cube in square and dividend square geometrics were considered and fabricated through Fused Deposition Modelling (FDM) technique. The proposed structures were additively manufactured with four different thermoplastic polymer based filament materials and their influence on the crashworthiness characteristics were investigated experimentally. The obtained results revealed that the PLA-CF based KC configuration exhibited SEA of 2.50 kJ/g and the maximum value of CFE is 84.91 % for PETG-CF based KC configuration. Furthermore, the experimental results indicated that the proposed thermoplastic polymer composite based lattice cubic structures are potentially a suitable component for crashworthiness applications owing to their significant energy absorption ability.
TL;DR: In this article , the effects of optimal compositions of Al-Mg-Si alloy reinforced with Palm Kernel Shell Ash (PKSA) particles on dynamic mechanical characteristics of the composite produced via the powder metallurgy route were investigated.
Abstract:
Due to heavy usage and rising populations, there is a growing need for local and naturally derived materials in the automotive and aerospace industries. Furthermore, due to their excellent mechanical qualities and high strength-to-weight ratio, composite materials are expected to perform better than traditional materials, particularly in automotive and aerospace applications. According to this perspective, this research aims to investigate the effects of optimal compositions of Al-Mg-Si alloy reinforced with Palm Kernel Shell Ash (PKSA) particles on dynamic mechanical characteristics of the composite produced via the powder metallurgy route. To evaluate the static tensile strength of the produced composites, PKSA compositions of 0, 2, 4, 6, 8, 10 and 12 weight percent as reinforcement on Al-Mg-Si powder were used. In this study, the damping factor, change in length, flexural, storage, and loss moduli were determined. In addition, the produced composites’ bulk density, hardness, creep, and Dynamic Mechanical Thermal Analysis (DMTA) were also investigated. According to the study’s morphology result, recrystallisation of the powdered composition during ball milling resulted in increased dislocation density and harder phases in the PKSA, contributing to the PKSA’s better characteristics. Furthermore, the optimum weight percentage of 6.0 weight percent of PKSA (Sample C4) has significant properties compared to the unreinforced (control) sample and was also found to have improved storage modulus, loss modulus, and damping behaviour. These findings showed that the developed composite, particularly sample C4, may be used in various technical applications, including automotive and aerospace industries.
TL;DR: In this article , the effect of various quantities of the clays on the loss on ignition (LOI), refractoriness (RF), and firing shrinkage (FS) of the blends was investigated.
Abstract: High-performance materials, systems, and processes have necessitated the exploration of very high-temperature environments. Materials, particularly ceramics, which can withstand these high temperatures, have been extensively studied, even though enough emphasis has not been given to clays sourced locally in Nigeria, where there is an abundance. Also, stochastic optimization techniques has been employed to improve on system or carry out experimentation with minimal spend of resources and very high accuracy. This work extensively explored the refractory properties of blends developed from locally sourced clays (Mayo Ndaga and kachalla Sembe and Kona). The Taguchi optimization technique was employed to determine the effect of various quantities of the clays on the loss on ignition (LOI), refractoriness (RF), and firing shrinkage (FS) of the blends. It was discovered that the optimum (lowest) LOI, highest RF, and lowest FS were 11%, 1333 °C, and 0.48%, respectively. Analysis of variance also proved the significance of Mayo Ndaga on the RF and FS of the blends, with P-values of 0.038 and 0.000 at a 95% confidence level.
TL;DR: In this paper , the motion of atoms or molecules at various temperatures and pressures was analyzed and visualised using the molecular dynamics simulation through large-scale atomic/molecular massively parallel simulator (LAMMPS).
Abstract: Molecular dynamics (MD) simulation continues to be one of the most advanced tools in a wide range of fields and applications. The motion of atoms or molecules at various temperatures and pressures was analysed and visualised using the MD simulation through large-scale atomic/molecular massively parallel simulator (LAMMPS). This research focuses on a basic introduction to MD, as well as their determination and MD methods. LAMMPS works with a variety of external packages to determine the position of atoms and molecules over time. As the simulation has various procedures such as algorithm to step processing and results, the developers of MD are constantly pushing for the reduction of pre-steps. This classifies the performance competence that should be approached for increased portability of performance on a programmatic level, a key to implementing the solution for various problems that would come from inventors and possibly new research in programming languages.
TL;DR: In this paper , a multiscale analysis method is developed by linking the molecular dynamics simulation and finite element homogenization analysis, which can accurately predict the elastic and shear moduli, and CTE of polymeric nanocomposites because of the clustering phenomenon.
Abstract: Thermo-mechanical properties of polymeric nanocomposites containing clustered nanoparticles are investigated using molecular dynamics (MD) simulation. Comparing between the dispersion and cluster models, it is revealed that the thermo-mechanical properties are decreased due to the clustering phenomenon. For effectively predicting the thermo-mechanical properties of polymeric nanocomposites, a multiscale analysis method is developed by linking the MD simulation and finite element homogenization analysis. Using the multiscale analysis, the elastic and shear moduli, and coefficient of thermal expansion (CTE) of the interphase can be obtained, and it is revealed that the reinforcement effect of the interphase is decreased due to the cluster phenomenon of nanoparticles. In addition, it is showed that this method can be used to accurately predict the elastic and shear moduli, and CTE of polymeric nanocomposites because of the clustering phenomenon.
TL;DR: In this paper , the impact and tribological properties of green composites with 30 wt.% hemp fibers reinforced polylactic acid (PLA) were evaluated under dry-sliding linearly reciprocating motion.
Abstract: In this study, green composites are prepared with 30 wt.% hemp fibers reinforced polylactic acid (PLA) to enhance the impact and tribological properties. Different surface treatments of alkali and silane, compatibilizer of maleic anhydride (MA), and blends of thermoplastic polyurethane (TPU) and poly (butylene succinate) were applied to improve interfacial adhesion between fibers and matrix. Hemp-reinforced PLA bio-composites were fabricated and characterized by hardness, impact strength, wear, and friction properties. The tribological tests of the injection-molded components were performed under two different loads (10 N and 20 N) as dry-sliding linearly reciprocating motion per ASTM G133. Modified composites gave better tribological properties than unmodified composites. While no remarkable improvement was observed in the hardness value of untreated fiber-reinforced composite, alkali-treated composite reached up to 43% improvement in hardness value. In general, as the load increased, weight loss increase was observed in all composites. Unmodified bio-composite exhibited a very low weight loss and specific wear rate (SWR) compared to neat PLA under 10 N load. The SWR of the MA bio-composite had the lowest value for both loads (10 N and 20 N) compared to the other bio-samples. The TPU blended bio-composite exhibited the highest impact strength (22.96 kJ m−2) after pure PLA (26.5 kJ m−2). Therefore, due to surface treatments and blends applied to the fibers, some composites’ hardness and wear resistance were increased while the impact strength and friction coefficient was decreased. Especially silane surface treatment and MA compatibilizer application increased the wear resistance of composites. When the scanning electron microscope images were examined, it was revealed that the fiber and matrix interface bonding was good, and the fibers were firmly embedded in the matrix. Furthermore, forming a protective thin film layer formed by the polymer debris from the surface during dry-sliding increased the wear performance of the bio-composites.
TL;DR: In this paper , the authors reviewed the critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application and provided an overall overview of the current state-of-the-art.
Abstract: Many engineering structures, especially defense applications, need to be reinforced against blast loads due to a nearby explosion. Today, much more attention needs to be given to this issue because of increased exposure to explosions, and natural disasters. Different solutions have been used in the literature to mitigate blast-loading effects. One of these applications, sandwich panels, are a good candidate for blast-loading applications. In a sandwich panel structure, several parameters have considerable effects on deflections, deformations, and energy absorption capability. The most important of these parameters are: (i) the material and thickness of the front and back face sheets and core; (ii) core density and grading; (iii) core and face sheet types; (iv) filling and stiffening strategies of the core; (v) radius of curvature of the panel; (vi) mass of explosive charge; and (vii) standoff distance. The aim of this paper is to review these critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application.
TL;DR: In this article , the optimal composition of reinforcement content (pumice powder and carbonated coal particles) and processing parameters (stirring speed, processing temperature, and stirring time) was determined to determine the thermal conductivity of the developed material.
Abstract: Aluminum metal matrix composites have been gaining traction in recent years due to their good mechanical properties and low weight. Particulate reinforcements for the improvement of its properties have been explored. This research aimed to determine the optimal composition of the reinforcement content (pumice powder and carbonated coal particles) and processing parameters (stirring speed, processing temperature, and stirring time) on the thermal conductivity of the developed material and also to characterize the constituents using x-ray fluorescence, x-ray diffraction, and scanning electron microscope/energy dispersive x-ray. The Taguchi optimization approach and regression analysis were used for the optimization and statistical analysis, respectively. The Taguchi optimization results gave an optimum thermal conductivity of 111.5, 112.5, 111.7, 112.9, and 112.4 W m−1 °C for pumice, carbonated coal, stirring speed, processing temperature, and stirring time respectively. The optimization also revealed the optimum setting for reinforcements and stir casting process factors as regards thermal conductivity to be 2.5%, 5.0%, 300 rpm, 850 °C, and 5 min for pumice powder, carbonated coal particles, stirring speed, temperature, and time, respectively. The optimal thermal conductivity of 120.40 W m−1 °C was obtained for the hybrid composite which gives a 131.54% improvement over the conventional grey cast iron brake disc. The particulate reinforcements (pumice powder and carbonated coal particles) and the processing factors all had significant effects on the thermal conductivity of the material, with the carbonated coal particles having the highest percentage contribution of 16.51%, as established by the analysis of variance. A model for predicting the thermal conductivity was developed using regression analysis, and high prediction accuracy was established with R-Square, R-Square (adj), and R-Square (pred) values of 94.68%, 88.60%, and 79.94%, respectively. The results of the characterization show the presence of hard compounds such as silica, iron oxide, and alumina in pumice powder and carbonated coal particles.
TL;DR: In this article , the effect of graphene nanoparticles on the strength of a sandwich panel structure based on foam core, which is inspired by the microstructure characteristics of dragonfly wings, has been investigated experimentally and numerically under low-velocity impact.
Abstract: The effect of graphene nanoparticles on the strength of a sandwich panel structure based on foam core, which is inspired by the microstructure characteristics of dragonfly wings, has been investigated experimentally and numerically under low-velocity impact. Sandwich panel structures are made of E-glass/epoxy layers, and different percentages of graphene nanoparticles and combined with their resin. Also, polyurethane foam was used for its central core. For numerical modeling, a nonlinear progressive damage model of composite and nano-composite shells is incorporated into the finite element (FE) code by VUMAT subroutine. The numerical results were compared with the collected experimental data and it shows that there is a good compatibility between them. To check the damage in the structures, the images of the cut view of the samples were taken from the damaged area, and the results were reported. In order to evaluate the distribution of graphene nanoparticles in the polymer structure, the manufactured samples were analyzed using the FE-scanning electron microscopy analysis device. It was concluded that this type of sandwich structure inspired by dragonfly wings can limit damage propagation and keep the rest of the structure healthy under low-velocity impact.
TL;DR: In this paper , the authors investigated the natural frequencies and loss factors of cylindrical sandwich shells composed of the viscoelastic core layer, surrounded by functionally graded graphene-platelet reinforced polymer composite (GPLRPC) and ceramic/metal (FG-ceramic/metal).
Abstract: In this paper, natural frequencies and loss factors of cylindrical sandwich shells composed of the viscoelastic core layer, surrounded by functionally graded graphene-platelet reinforced polymer composite (FG-GPLRPC) and ceramic/metal (FG-ceramic/metal) are investigated. The viscoelastic layer is modeled via the fourth parameter fractional viscoelastic pattern, and the functionally graded ceramic/metal layer is theoretically modeled using a power-law function. The uniform, symmetric and un-symmetric patterns are considered for simulating the graphene platelet (GPL) nanofillers distributions along with the thickness direction. The classical shell theory is used for functionally graded layers and properties of the effective materials of GPLRPC multilayers are determined by using a modified Halpin–Tsai micromechanics model and the rule of mixture. The governing equations of motion are extracted by applying the Lagrange equation and the Rayleigh-Ritz method. The determinant of the coefficient matrix of the characteristic equation is calculated, and the natural frequencies and loss factors of the system are extracted. A study of the interactions of materials and geometrical factors such as the ratio of radius to length, the properties of functionally graded materials, and GPL weight fractions for patterns of proposed distributions are presented and some conclusions have been formed.