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To prove that calcium alginate beads can be used as scaffolds during in vitro culture.

This article investigates the sliding wear behavior of ZTA (zirconia toughened alumina) particle (ZTAp)- and NbC (niobium carbide) particle (NbCp)-reinforced Fe60 matrix composites (ZTAp–NbCp/Fe60). ZTAp–NbCp/Fe60 was produced through vacuum sintering and tested on an M-2000 wear-testing machine. As revealed by the results, the wear loss increased with the increase in rotation speed and load. Abrasive wear occurred in the mild wear region; adhesive wear and serious abrasive occurred in the moderate wear region; and fatigue wear and ZTAp broken occurred in the severe wear region. According to the aforementioned conclusions, a more clean and intuitive wear mechanism diagram was established. In the process of wear, ZTAp was well combined with the matrix, and there was no crack at the interface. Meanwhile, in the wear process, ZTAp could block furrow, weaken the wear of the micro-convex ring, and improve the sliding wear performance of the composite material.

The aim of this study is to investigate an approach to the electricity conductivity of nano-graphite in concrete by experiments, and different doses of nano-graphite have a different influence on the electrical conductivity of the whole structure. In this research project, the compression test was carried out on a 50 mm × 100 mm cylinder using a Baldwin machine and a digital multimeter to measure the conductivity. To find out the patterns of how different nano-graphites influence the properties of concrete structures, multifarious percentages of nano-graphite’s content are employed for testing both the electrical resistivity and compressive strength. These results are important to predict and prevent structural failure and fill the gap in nano-graphene concrete research, thereby saving human lives and significantly reducing the structures’ cost of maintenance and repair.

Carbon/silica composite (C/SiO2) aerogels were synthesized by using tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, trimethylchlorosilane, resorcinol as the silicon and carbon sources, and ethanol as solvent, via the sol–gel process followed by supercritical ethanol drying and thermal treatment. The influence of thermal treatment process on the structure of C/SiO2 composite aerogels was analyzed mainly and measured by Fourier transform infrared spectrometer, X-ray diffraction and nitrogen adsorption–desorption analysis. The results showed that the optimum thermal treatment temperature of C/SiO2 composite aerogels was 1,300°C. With the increase in the thermal treatment time, the linear shrinkage of the composite aerogels increased gradually, and the pore volume, average pore diameter and specific surface area of the composite aerogels increased first and then decreased.

SiC fiber-reinforced SiC matrix composites (SiCf/SiC) with 2D woven fabric as preform were tested under compression with in-situ X-ray computed tomography. The microstructure and damage evolution of the material under continuous loading levels were accurately revealed by image reconstruction of CT data. There were inhomogeneous pores in SiCf/SiC composite because of the un-uniform fiber distribution in the preform. The result also showed that 2D woven SiCf/SiC composite had obvious non-linear characteristics by its compressive load–displacement curve, and the damage modes included transverse matrix cracking, interlayer cracking, longitudinal matrix cracking, and fiber bundle fracture. Matrix cracking tended to occur near the pores or holes of the material, and the number of longitudinal cracks was relatively high compared to the number of transverse cracks.

Glass Fiber Reinforced Polymer (GFRP) is widely used as aerospace material requiring high specific strength, specific stiffness, and excellent mechanical and chemical properties. To apply the already approved composite materials to other processes, an equivalency test that compares the mechanical properties of the composite materials based on the database is required. For the successful completion of the equivalency test, it is important to control the factors affecting the mechanical properties. The resin content and density of the specimens are manufactured differently according to the process. The effect of these factors on the change of mechanical properties required for equivalency qualification has not been sufficiently reported. In this study, an equivalency test was performed on the GFRP applied to the aircraft radome based on the procedure of the equivalency test and acceptance test proposed by the National Center for Advanced Materials Performance. The causes of problems occurring between equivalency tests were analyzed. It was confirmed that the resin content, density, and voids of the specimen affect the mechanical properties. As the resin content decreases, the density and voids were controlled, and it was confirmed that the average strength and modulus increase by 13.12 and 6.78%, respectively. The equivalency qualification was completed by applying an improved process in which these factors were controlled.

The low-velocity impact and compression after the impact of the composite stiffened panels were carried out after damp-heat aging. The experimental results show that reinforcing the ribs can enhance the impact resistance of test pieces after damp-heat aging. After impacting, the specimens were tested in an axial compression. The results show that the ultimate bearing capacity of the specimen is also affected by different located positions of the impact and different aging times. Compared with the intact specimen, the ultimate load-bearing capacity was reduced to 16.83, 12.10, and 17.10% with the specimen aging for 0, 45, and 90 days, respectively, while the impact position located at the intersection of longitudinal and transverse bars has the greatest influence on the damp-heat aging of specimens.

In order to evaluate the effect of rare earth Y2O3 on the wear and corrosion properties of WC–Ni composite coatings, X-ray diffraction, scanning electron microscopy(SEM), electrochemical polarization curve, electrochemical impedance spectroscopy (EIS), and friction and wear tests were used to analyze the metallographic structure, corrosion characteristics in simulated seawater and friction and wear principle of the composite coatings. Results of SEM revealed that the microstructure of the Y2O3 added coatings was refined with the grains changing smaller and the impurity disappearing. The EIS results proved that the addition of Y2O3 brought a positive influence on the corrosion resistance by reducing the capacitance and increasing the R f and R c. The hardness of the coatings with Y2O3 addition tends to be smooth without wild fluctuation, and the coating with 0.5 wt% Y2O3 owned the hardness values reaching 850 HV. With the addition of rare earth elements, the coefficient of fiction values decreased, reaching the lowest (0.3418) at the content of Y2O3 of 0.5 wt%. The surface of the coating without Y2O3 appears grooved due to the abrasive wear; the coatings with Y2O3 did not suffer serious wear and tear. The coating with 0.5 wt% Y2O3 exhibited the best corrosion resistance and wear resistance properties in all the specimens.

To improve the mechanical properties and corrosion resistance of the hydraulic column in the mine, a semiconductor fiber-coupled laser was used to laser-clad iron-based alloy powder on a 27SiMn steel substrate (SUB). The microstructure, mechanical properties, and corrosion resistance of the obtained cladding layer (CL) were studied based on experiments. Results show that equiaxed grains at the top of the CL are fine and tightly arranged. Compared with the SUB, the CL average microhardness is increased by 0.3 times, the average friction coefficient is decreased by 0.12, and the wear amount is significantly reduced. The bonding strength between the CL and the SUB is good, and the tensile strength is increased by 10.82%. Compared with the SUB, the mechanical properties and corrosion resistance of the CL are better. The research has an important guiding significance for the practice of hydraulic column repair and strengthening engineering.

The study aims to optimize the composition of the main composite, the components of which, in their joint presence, make it possible to obtain the most significant positive synergistic effect. The authors of this article used the fibers of fly ash from thermal power plants as a finely dispersed component added to the crushed stone sand mixture. The result of the study was a high-strength corrosion-resistant material consisting of a crushed stone sand mixture (CSSM) with the addition of the fibers of fly ash. The authors applied the thermogravimetric and standard methods to study and determine the performance and strength characteristics of the obtained material. The combined effect of a complex organic-mineral modifying additive and the cement with the fibers of fly ash provided a compacted and reinforced structure of cement stone. An optimal binder composition was developed, consisting of cement and fiber of fly ash. The authors of this article examined the physical-mechanical and structural-mechanical properties of a CSSM of fine-grained concrete reinforced with a complex additive of cement, fibers of fly ash, and a superplasticizer. The study also provided technological solutions for manufacturing a functional mixture of fine-grained concrete based on the developed complex organic-mineral additive.

The purpose of this article is to evaluate four different gas turbine cogeneration cycles which are basic, absorption cooling, air heating and air fuel heating cogeneration cycles by using the most important six evaluation criteria for different excess air coefficient, different compression rates, and different compressor inlet air temperatures. These six evaluation criteria are electrical heat ratio, exergy efficiency, incremental heat rate, artificial thermal efficiency, fuel energy saving ratio, and specific fuel consumption. It is seen that the air-fuel heating cogeneration cycle is the most efficient among the cycles examined for a certain compressor compression ratio, followed by the air heating, basic, and absorption cooling cycles.

This article focuses on an experimental study of the flexural response of a polymer composite laminate (CL) reinforced with a plain weave carbon fiber fabric. The aim of this research is to investigate the effect of the span length-to-specimen thickness ratio on the flexural properties of the selected CL. The laminate specimens were tested in the three-point flexure configuration for span length-to-specimen thickness ratios of 16, 20, 32, 40 and 60. The investigations were carried out to identify on-axis and 45° off-axis flexural responses of the CL. For this reason, two types of rectangular flat specimens were prepared, differing in reinforcement orientation relative to the support span. Using the special code, the lay-up of the specimens was designated as [(0/90)F]8 and [±45 F]8, respectively. It was found that the flexural modulus and flexural strength of the specimens depend on the span length-to-specimen thickness ratio. Despite testing the same CL, the response of the specimens to the change in the span length is different. In addition, it was concluded that the span length also has a significant influence on the final failure of the laminate specimens.

The uniformity of the monofilament diameter plays a key role in the performance of continuous filament yarns and their subsequent products. However, traditional methods for measuring fiber or filament diameters focus on estimating the arithmetic mean data, and only part of the diameter data can be obtained. Additionally, most of these traditional methods require complex sample preparations, such as by making cross-sectional slice samples. This study intends to present a simple method for measuring almost all of the monofilament diameters in a single yarn. It is not necessary to make slice samples. After the yarn sample or fabric sample is taken and prepared, synthetic laser images can be obtained directly by scanning the cross section of the sample with a 3D laser scanning confocal microscope. According to the results of many experiments, more than 90% of the monofilament diameters of a single yarn can be measured. The result also shows that the difference in the diameter data between the traditional method and the synthetic laser imaging method is less than 2%. This method presents the differences between the majority of monofilament diameters, and the yarn clustering property can be evaluated by the sum of the monofilament diameters and the yarn cross-sectional area.

In this work, we studied the failure mechanism of steel–polypropylene hybrid fiber reinforced concrete (HFRC) at the mesolevel. The uniaxial tensile test of HFRC was simulated using ABAQUS finite element analysis software. Then, the relationship between the mesoscale failure process and the mechanical properties was analyzed based on the simulation results. The results showed that the cracks first appeared in the interfacial transition zone and then gradually propagated into the mortar elements and intersected with adjacent cracks, forming major macroscopic cracks. According to the crack evolution process, the incorporation of steel fibers and polypropylene fibers changed the concrete crack expansion paths and served to inhibit crack expansion. Furthermore, the increase in the hybrid fiber volume had a positive effect on the mechanical properties, and the steel fibers dominated in providing reinforcement compared to the polypropylene fibers.

In this article, aiming at the problems of low mechanical properties and the unstable structure of the binder in inorganic artificial stone, performance improvements were studied. The effects of 12 materials of blast-furnace slag (BFS), fly ash (FA), and kaolin on the properties and microstructure of inorganic binders were systematically studied and analyzed. As a result, the compressive strength of BFS-2, FA-1, and FA-2 binder was increased by 10.0, 6.0, and 1.5%, and the flexural strength was increased by 44.8, 79.2, and 1.3%, respectively. It was worth noting that BFS and FA could effectively promote hydration reactions due to active materials and boost the growth of C–S–H and CH, leading to the inorganic binder forming a stable structure. Thus, this work systematically designs and prepares inorganic binders with high compressive strength and excellent flexural strength. This reveals how inorganic materials affect the properties of inorganic binders on the microstructure and offer a new idea for the development of this field.

This article describes work concerning the compressive properties in hygrothermal environment of three-dimensional (3D) five-directional braided composites. Hygrothermal aging tests at temperatures of 40, 60, and 80°C and compression tests were carried out on the specimens with three braiding angles of 15, 25, and 35°. The surface morphologies of the samples taken using scanning electron microscope before and after the hygrothermal aging test were used to analyze the influence of the hygrothermal environment on the internal structure of braided composites. The experimental results indicate that the hygrothermal environment has a more influence on the specimens with a braiding angle of 15°, and the greater the moisture absorption percentage, the lower the retention ratios of compressive strength and modulus. Compared with room temperature, the compressive strength and modulus of specimens with a braiding angle of 15° reduced by 72.2 and 82.7% as the water bath temperature increased from 40 to 80°C. Moreover, the failure mechanisms of 3D five-directional braided composites in the hygrothermal environment were analyzed.

The viscosity characteristic is an important factor affecting the holding rate of the meal-assisting instrument. The effects of shear rheological properties, thixotropy, and pasting properties of xanthan gum (XG), guar gum (GG), and thorn bean gum (TBG) in deionized water, berry juice (BJ), and nut lotus root starch (NLRS) were investigated using a rotational viscometer and a water bath, respectively. The results indicated that all samples exhibited non-Newtonian shear-thinning behavior, the flow behavior index (n) was less than 0.5 indicating strong pseudoplasticity, the consistency index (K) decreased sequentially from TBG, GG, to XG, and there was a significant difference between yield stress and concentration (P < 0.05). The hysteresis loop area (∆S) decreases sequentially from NLRS, BJ, to DIW, and the activation energy (Ea{E}_{{\rm{a}}}) decreases significantly with the increase in concentration (P < 0.05). This study has a reference value for improving the holding rate of sticky meals.

There are a large number of natural gas shows in the Upper Paleozoic of the central Hunan Basin. However, the hydrocarbon accumulation process was complicated due to the strong tectonic reformation in this area. A study of the natural gas accumulation period is of significance for determining gas accumulation models. In this research, the fluid inclusion samples were tested, the fluid inclusion occurrence characteristics, uniform temperature data, and reservoir evolution were analyzed, and four diagenetic periods and four diagenetic periods and three hydrocarbon accumulation periods were identified. (i) For the syntaxial stage, the filling is dark and nonluminous, and the fluid captured by the overgrowing cement around the particles is mainly seawater; (ii) for the (Early) Mesogenetic burial stage, the calcite cement grows around the particles or micritic calcite matrix, and the fluid captured is mainly brine; (iii) for (Late) Mesogenetic burial stage, two sets of decomposed fissures developed in massive calcite colloids with non-luminous gas-rich hydrocarbon inclusions within the crystals; and (iv) for Telogenetic burial stage, weakly fluorescent pure gaseous hydrocarbon inclusions are developed in luminescent calcite veins. The result indicates that the organic inclusions in the Lower Carboniferous of the central Hunan Basin are dominated by weakly fluorescent and nonfluorescent rich gas inclusions and pure gas-phase inclusions, with three stages of hydrocarbon filling. By integrating the average homogenization temperatures on burial curves, the three charging orders correspond to 260–250 Ma during the Late Permian, 249–245 Ma during the Early Triassic, and 208–170 Ma during the Late Triassic. Dense reservoir characteristics reveal deep basin gas reservoir in deep basin.

To comprehend the fatigue failure mechanism at the fiber discontinuity in fiber-reinforced composites, it is necessary to evaluate the local mechanical behaviors. The fatigue strength depends on the stress distribution at the fiber inclusion corner. An improved advanced finite element method (IAFEM) is proposed for the stress intensity factor (SIF) analysis at the fiber inclusion corner. In the IAFEM, the element stiffness matrix of singular inclusion corner element (SICE) is obtained, and the singular elastic field at the tip of the fiber inclusion is determined. The effects of load direction, fiber distribution, fiber geometry, and material properties on SIFs are analyzed numerically using the IAFEM. The difference in stress field distribution between two-dimensional and three-dimensional fiber inclusions is discussed. The IAFEIM and calculation results can provide reference for fatigue strength analysis and preparation of composite materials.

During processing and bubble growth processes, the melt viscosity changes with temperature, pressure, and blowing agent concentration. Therefore, measurement and prediction methods for viscosity characterization in terms of temperature, pressure, and blowing agent dependency are needed. This study demonstrates the applicability of in-line viscosity measurements during the foam injection molding process and a model for viscosity superposition and prediction. In the present study, polystyrene and a modified polylactide for foaming applications with nitrogen as blowing agent are investigated. By changing the injection speed, temperature, and blowing agent concentration, the process conditions are varied, and thus the resulting pressure drops within the in-line measurement die. The calculated shear rates and viscosities are shifted to a master curve by the application of superposition principles. The viscosity dependency on temperature is described by the Arrhenius equation, the pressure by the Barus equation, and for the blowing agent concentration, a novel Barus-like equation was derived and applied. The prediction of the master curve viscosity function was achieved by the power-law model in combination with the superposition principles and showed good agreement with the shifted in-line data. Finally, the in-line measurements and viscosity predictions are validated by comparing them to rotational and capillary rheometer measurements.

Honeycomb materials are widely used across engineering fields. The use of honeycomb sandwich structures as energy dissipation and impact protection materials for reinforced concrete components in the field of civil engineering is a novel concept. Therefore, it is of great significance to study the energy absorption characteristics, dynamic response theoretical model, and collapse energy dissipation theory for the use of honeycomb sandwich structures as protective materials. Based on the large-scale low-speed pendulum impact test and the corresponding finite element model, this study establishes an ideal model for the honeycomb sandwich panel under the impact of a square flat head and gives the corresponding theoretical derivation. At the same time, it puts forward a method to estimate the energy consumption and dynamic crushing distance based on the energy consumption theory angle of the covering layer.

This article was designed with a plurality of impact tests of three-dimensional four-directional braided composites, and the impact response of specimen impacted by a circular punch was studied. Ultrasonic C-scanning was used to detect the internal damage area to study the damage propagation process under multiple impact loads. The finite-element software ABAQUS was used to model the meso-structure of three-dimensional four-directional braided composites. Based on material characteristics, the three-dimensional Hashin damage criterion was used for the fiber bundle, and the maximum stress criterion was used for the matrix to judge the material damage. Combined with test and simulation results, the failure mode and damage evolution process of the specimen under multiple impact loads were studied. The results showed that the impact resistance of the three-dimensional woven composite material is affected by the braided angle. The larger the braided angle of the specimen, the better the impact resistance. The damaged area of the large braided angle material expanded to the periphery, and the damaged area of the small braided angle material was primarily developed in the longitudinal direction. The failure modes of the specimen during the impact process were primarily a longitudinal tensile failure of fiber bundles, transverse tensile failure and transverse compression failure of fiber bundles and matrix.

Modern materials science has faced the problem of reducing the cost of raw materials and labor costs while obtaining basic construction materials (cement concrete) with increased performance properties. The article aims to substantiate the use of carbon nanotubes of fly ash as a cement concrete modifier to be reasonable for solving the above problem. Experimental studies are carried out using standard and special methods. The technological properties of cement concrete mixtures are determined in accordance with the European and American standards. The study investigates the impact of carbon nanotubes of fly ash on the structure and properties of the mineral Portland cement binder. The article provides the examination of structural and rheological characteristics of nano-modified cement concrete mixtures. The effect of a carbon nano-modifier on the strength, deformation, and performance properties of cement concrete mixtures is defined. As a result, the optimal composition of nano-modified cement concrete mixture has been developed that meets the criteria of concrete compressive strength and flowability. Positive research results allow determining the areas of application of the obtained compositions in civil engineering.

The viscosities of poly(3-hydroxybutyrate) (PHB) with mixed tacticities were determined as functions of temperature and shearing rate via plate–plate viscosimetry, and fitted by a combined Herschel–Bulkley–Cross–Doolittle model while applying Carvalho et al.’s single-point correction. They were compared to values of slit viscosimetry, obtained during processing at a temperature of 428 K. In both cases, measured values and fitted model parameters as a function of tacticity exhibited a discontinuous behaviour at a fraction of meso diads of 0.7. To further investigate, we calculated values of vibrational and excess free volume. We found that these correlate with structural and external properties, some of which were reported in earlier works, namely the paracrystalline contents and specific volumes of the materials at room temperature, as well as their energies of fracture during tensile testing. These, in turn, correlate with the statistical averages of relative lengths of chain segments of similar a- or iso-tacticity. Hence, we found that expressing changing tacticities simply by a continuous progression of the fraction of meso diads is insufficient to trace associated discontinuities of the flow behaviour in mixed-tacticity PHB. We conclude that free volume is generated by polymer chain conformational disorder, which should be treated on the oligomeric chain segment level.

Composite sections are found to be a novel technique in modern day scenario of construction. This stands tall than the ordinary and conventional type of constructions. Columns as a structural element play a vital role in structural frame. This research comments on the behavior of composite columns. The main objective of this study is to analyze the behavior of steel-encased concrete composite columns as experimentally under axial compression and the mode of failure under ultimate failure and yield point. The steel-concrete composite system combines the formability and rigidity of reinforced concrete with the ductility and strength of structural steel to meet the demand for earthquake-resistant constructions. Three specimens were chosen for this study: one was a composite column, the other two were ordinary RC columns and structural steel columns. The raw materials' natural properties are assessed. As a result, material testing for cement, fine aggregate, and coarse aggregate was completed, as well as a concrete mix design. A comparative analysis of the local and post-local buckling behavior of different composite sections has been studied and the column sections have been designed according to Eurocode 4 (ENV 1994) to determine the plastic resistance of the section. These three specimens underwent compression test and the results are tabulated and compared. The corrosion resistance and fireproof nature (resistance to fire at higher temperatures) that are transmitted into the member are related to the steel being encased within the concrete. These are the two major drawbacks of any steel construction combined with an earthquake-resistant structure. Rather than a traditional steel construction, earthquake structures benefit from this type of load handling capabilities. The portion can be used before it completely collapses if proper design factors are taken into account.

This article used the strip element method to study the dynamics problems of the functionally graded plate with variable gradient parameters under the harmonic loads. The dynamic model of the functionally graded plate is established by using the strip element method, the rationality and accuracy of the theoretical results are verified by finite element method, and the displacement response under different gradient parameters is also calculated. The results show that under the different gradient parameters, the displacement varies harmonically with time, and with the increase of gradient parameters, the fluctuation period of displacement with time increases continuously, and the displacement peak also gradually increases. The displacement along the thickness direction also shows the harmonic form. Through comparison, it is found that the gradient parameters have a greater impact on the dynamic response for the functionally graded plate; with the increase in the gradient parameters, the displacement response also increases, but the displacement response trend slows down.

A novel separating device, Inertial particle separator (IPS), has been developed recently to separate solid particles and to protect the turbine engine from particle erosion damage. Herein first, an advanced model based on IPS was proposed to investigate the deformational behavior of deformable particle separator, and to meet the higher requirements of sand discharge and pneumatic demand, which are operated under hostile working conditions or environments and severe climate conditions. We established a three-dimensional (3D) nonlinear finite element analysis (FEA) model of bump consequently, which was the core of centerbody. The essential material parameters of the FEA model were obtained via experimental data (tensile testing). By comparing the influence of these factors (pressure and laying angle), the deformational behavior of the centerbody was discussed. Finally, based on the simulation results with the experimental data (Schlieren testing), the model was found to perform with high reliability and accuracy, demonstrating the great capability in precisely predicting the deformational characteristics of the bump under practical working environments.

The water-lubricated bearing is mainly installed at the stern of the ship to support the rotation of the main shaft of the ship, which is an important component of the ship’s power plant. The rubber stave of the water-lubricated bearing acts as an elastic body, which can effectively suppress the rotational vibration of the rotating shaft and improve the shaft alignment effect. To monitor the operational status of the water-lubricated bearing at the stern of a ship, a design method of smart rubber stave for water-lubricated bearings is proposed in this article. According to the structure of the rubber stave, the packaging and protection form of the optical fiber, the forming process of the rubber stave, and the mechanical analysis were carried out to determine the distribution design principle of the fiber Bragg grating (FBG) in the rubber stave. Then, FBGs were packaged, protected, and implanted with an uneven distribution into the rubber stave to achieve force sensing in the bearing. With reference to the force state of the water-lubricated bearing during shipbuilding and ship operation, various types of condition monitoring tests were conducted on the smart rubber stave using an elastomer testing machine, which were to analyze the effects of load sizes, frequencies, and ambient temperatures. The tests showed that the FBGs in the rubber stave could monitor the static and dynamic loads of the bearing under the seawater environment or inland water environment below 30°C. This method can be used for the smart designing and online load condition monitoring of water-lubricated bearings.

The effect of carbon fiber Z-pin on carbon fiber composite under moisture condition with and without flexural load was investigated in this work. Moisture absorption property and crack propagation of carbon fiber reinforced epoxy matrix composite and Z-pinned composite were evaluated under moisture only and moisture-coupled load conditions. The moisture property was evaluated by moisture content and microscopic morphology obtained using X-ray micro-computed tomography (X-ray μCT). The microstructures inside composites and Z-pinned composites after moisture conditions and three-point flexural test were detected using X-ray μCT and optical microscope. It illustrates that the moisture content of Z-pinned composites is higher due to the rich-resin pocket brought by the implantation of Z-pin. The cracks are obvious inside Z-pinned composites after moisture-coupled load conditions. It is attributed to the implantation of each pin which is the weak point for stress concentration and crack formation. Failure morphologies on the surface of composites and Z-pinned composites are different under different moisture conditions. Less macro-interlayer cracks are detected on the surface of Z-pinned composites, and plenty of microcracks initiating from pins are observed.

In this article, the concept of low-velocity impact resistance in composite materials is presented. Three existing expressions (e.g., bilinear, parabola, and exponential) that show the relationship between the dent depth and impact energy of composite laminates subjected to low-velocity impact are presented. Because of some flaws in these expressions, new supposed functions between impact energy and impact dent have been established. By means of existing ASTM D 7136 tests and simulation analysis, the new expressions are verified, and the nature of dent formation in composite materials is well explained. The conclusion is reflected in the ending part.

In order to quantitatively analyze the mesoscopic damage process of hydroxyl-terminated polybutadiene composite solid propellant under external load, periodic boundary conditions were applied to the representative volume element model based on sample composition and morphology, the mixed matrix containing aluminum powder was homogenized, and the hyperelastic matrix damage and bilinear/exponential particle–matrix interface cohesive model with initial damage were compiled through the secondary development of Abaqus. At the same time, a data interaction platform was constructed by means of Python and MATLAB, matrix and cohesion parameters were inverted according to the optimization algorithm and experimental data, and the whole process of propellant damage and fracture was simulated from the mesoscopic perspective. The results show that combining the adaptive particle swarm optimization algorithm and the Hooke–Jeeves algorithm can achieve the global optimal parameter inversion in 102 calculations, compared with the single local search algorithm, which can cut about 11% of the objective function values. Considering the matrix damage and the exponential cohesion model with initial damage, the optimal objective function value is 0.01635, which can more accurately simulate the propellant damage and fracture process compared with 0.02136 of a bilinear cohesion model.

The freeze-thaw (FT) damage characteristics of granite after different FT cycles were studied using computed tomography (CT) images. The three-dimensional (3D) volume numbers in the image were extracted to obtain the 3D pore structure of representative volume elements (RVEs) of granite under different FT cycles. The CT images of granite after 80 FT cycles were selected to draw reference lines for quantitative analysis of the distribution of meso-cracks in granite after FT cycles. Subsequently, a finite element model was established to explore the mechanical properties of minerals in granite during a single FT process. The results show that the FT damage inside the granite exhibits fracture characteristics, and the number of internal cracks, cracks area, and voxel porosity increase with the increase of FT cycles. After 80 FT cycles, the distribution of meso-cracks on the cross-section of granite exhibits significant anisotropy, and the distribution density and variation coefficient of meso-cracks vary with the dip direction angle of the reference line. The maximum principal stress and strain in the finite element model are negatively related to temperature. The maximum principal stress and strain of biotite minerals are consistently higher than those of feldspar and mica during FT cycles. The results can provide a reference for exploring the internal mechanism of the weakening of mechanical properties of granite microstructure caused by FT damage in cold regions.

Mixing and homogenization in anaerobic digesters are affected by the flow curve of sludge. The aim of this study is to mathematically express the flow curve of dense anaerobically digested sludge behaving as thixotropic and pseudoplastic fluids. Time-dependent changes in two pseudoplastic parameters, i.e., consistency index (µ p) and pseudoplastic index (n), by shear are modeled using a second-order kinetic equation with a coefficient that includes the power function of the shear strain rate. The calculated results are consistent with the experimental results. The kinetic parameters that yielded the ultimate values after shearing were associated with the sludge concentration, unlike the other kinetic parameters.

Study of mechanical properties of rock under hydro-mechanical coupling. The MTS815 rock mechanics system is used to perform triaxial compression tests of water-saturated sandstones under different confining pressures and pore water pressures. The results show that the peak deviation stress and its corresponding axial strain, residual deviation stress, initial deviation stress of dilation and deformation modulus of water-saturated sandstone are related to pore water pressure and confining pressure. They decrease with the increase of pore water pressure and increase with the increase of confining pressure. Poisson’s ratio and angle of rupture of water-saturated sandstone increase with pore water pressure. Based on the effective stress principle and Mohr–Coulomb criterion, the effective cohesion and effective residual cohesion of sandstone are 11.49 and 3.13 MPa, respectively, and the effective angle of internal friction and effective residual angle of internal friction are 38.32° and 25.32°, respectively. In addition, according to the variation relationship of sandstone strength, the relative strength criterion of sandstone under hydro-mechanical coupling is established.

Landslides caused countless economic and casualty losses in China, especially in mountainous and hilly areas. Landslide susceptibility mapping is an important approach and tool for landslide disaster prevention and control. This study presents a landslide susceptibility assessment using frequency ratio (FR) and index of entropy (IOE) models within a geographical information system for She County in the mountainous region of South Anhui, China. First, the landslide locations were ascertained in the study area using historical landslide records, aerial photographs, and multiple field surveys. In all, 502 landslides were identified and randomly divided into two groups as training (70%) and validation (30%) datasets. Additionally, the landslide-influencing factors, including slope angle, slope aspect, curvature, landform, lithology, distance to faults, distance to roads, distance to rivers, rainfall, and normalized difference vegetation index, were selected and their relative importance and weights were determined by FR and IOE models. The results show that the very high and high susceptibility classes cover nearly 50% of the study area. Finally, the comprehensive performance of the two models was validated and compared using receiver operating characteristic curves. The results demonstrated that the IOE model with the area under the curve (AUC) of 0.802, which is slightly better in prediction than the FR model (AUC = 0.786). The interpretation of the susceptibility map indicated that landform, slope degree, and distance to rivers plays a major role in landslide occurrence and distribution. The research results can be used for preliminary land use planning and hazard mitigation purposes.

In this article, the pipeline design is introduced. The new pipe structure is made of new fiber metal laminates with the unidirectional composite and sheet metal (Ti–Ni alloy). Many pipe structures are in the heating environment such as in or around the engine, which will also cause the heating-up structure. If the shape memory alloy (SMA) fiber is added to the composite lamination, it can be seen that with the increase of temperature, the stiffness of the structure is increased and so is its frequency. The changed frequency of the structure can avoid the excitation frequency in this way, which effectively inhibits the resonance. In dynamic analysis, it can also show that the pipeline with the SMA fiber has good performance for vibration reduction and noise attenuation. Additionally, the convergence of the meshing model and the effect of the thickness of the SMA material on vibration and noise reduction are also discussed.

Based on the thick-wall cylinder theory and composite material mechanics, the stress distribution model of the CFRP shaft tube and metal shaft head has been established, and the relationship between the layup parameters and the value of interference on the maximum assembly force and failure torque in the interference fit joints of the CFRP shaft tube and the metal shaft head is deduced. Combining the three-dimensional finite element analysis model with experimental data, the result shows that the layup angles of the CFRP shaft tube have a greater influence on the joint connection performance than the layup sequence, and the larger the layup angle, the better the joint assembly performance while keeping the value of interference constant. The maximum assembly force and failure torque of the interference fit joints increase linearly while the value of the interference amount increases when the layup parameters are constant.

Melanin comes from a wide range of sources. It can be isolated and characterized from some plants, animals and microorganisms, and can also be simply polymerized by dopamine. It has many biological properties such as antioxidant, ultraviolet shielding and bacteriostasis. Based on the above characteristics, the addition of melanin to film-forming materials can improve the relevant physical properties and functional properties of the film. In this article, the structure and properties of melanin were briefly introduced, and then the advantages and related research progress of melanin as a functional filler in the field of composite film were summarized.

A graphene hybridizing polyurethane/polyethyl methacrylate (GR-PU/PEMA) damping composite was synthesized using the sequential interpenetration method. The effects of the graphene content and the microphase separation structure on the damping properties, thermal stability, and mechanical properties have been studied in detail. The dynamic mechanical analysis indicated that graphene could improve the damping peak value of PU/PEMA, and the microphase separation structure could be beneficial for broadening the damping temperature range. The damping peak (tan σ max) of PU/PEMA hybridizing with 0.5 wt% graphene reached 0.82, and the temperature range of the loss factor (tan σ ≥ 0.3) was expanded to 88.3°C. Analysis of scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering reveals that graphene is uniformly dispersed in the polymer matrix, and the composite with interpenetrating polymer network (IPN) shows more microphase separation structures. Fourier transform infrared analysis indicated that there is strong interaction between graphene and IPN matrix. Furthermore, the addition of graphene improved the mechanical properties and thermal stability of composites.

In the existing composite four-rail electromagnetic launcher (CFREL), the armature and rail contact surface produces significant heat and bears considerable wear, thereby reducing the potential amount of electromagnetic thrust to be generated. To eliminate the damage caused by the thermal effect of the rail contact surface and to meet the electromagnetic thrust demand of the load, a CFREL is proposed. The proposed CFREL model is constructed, and the launcher’s electromagnetic characteristics are simulated and compared using the finite element method. The current density, distribution of magnetic flux density, and electromagnetic thrust characteristics are analysed. The results showed that the proposed CFREL reduced the maximum current density of the contact surface and effectively eliminated the current concentration of the armature and rail contact surfaces. Effective magnetic field shielding is realised with a larger range, which can better meet the requirements of the intelligent load’s magnetic field environment and provide stronger electromagnetic thrust for the load, hence solving the problem of insufficient thrust.

Cemented sand and gravel (CSG) is a new type of dam-building material. Aiming at the cumbersome process and long calculation time of traditional methods to invert the meso-parameters, a mesophase parameter inversion method based on Box-Behnken Design response surface was proposed. By constructing a response surface simulation test scheme with different inversion parameters (elastic modulus of aggregates, mortars and interfaces, and interfacial tensile strength), the stochastic aggregate model is used to complete the numerical simulation of the damage process, and different results are obtained. The equation between the response variable (stress at different loading times) and the independent variable (inversion parameter) was verified, and the rationality of the response model was verified; the action mechanism of mesophase parameters at different stages on the mechanical properties of the specimen was analysed. The test results are brought into the response surface model, and the meso-parameters are obtained by inverse analysis. The stress–strain curve obtained by numerical simulation with this parameter has an error of 1.1% at the peak stress and 3.27% at the peak strain. The accuracy is high, the number of test groups is much smaller than other conventional inversion methods, and has feasibility of application in CSG.

Through hot compression experiments at temperatures ranging from 603 to 723 K and strain rates ranging from 0.01 to 10 s−1, the hot deformation behavior of a 0.5 wt% graphene nanoplatelet-reinforced aluminum (0.5 wt% GNP/Al) composite prepared by the powder metallurgy method was studied. The constitutive equations obtained by mathematical models and a neural network were evaluated. The deformation property of the composite can be better described by the Johnson–Cook (JC) constitutive model optimized by establishing a relationship between the coefficient and variables obtained in the hot compression test, with a correlation coefficient (R) reaching 99.97% with the average relative error of 0.37% (98.1 and 4.17%, respectively, before optimization). Compared with the JC model, the neural network has perfect calculation accuracy and whole-process effectiveness, providing expanded and more accurate constitutive equations for subsequent simulations and for building the dynamic recrystallization model of the composite. The dynamic recrystallization model, hot processing map, and EBSD results are in agreement with each other and indicate that the optimal strain rate and temperature range of the composite are 0.01–0.1 s−1 and 693–723 K, respectively.

Continuous fiber-reinforced thermoplastics (CFRTs) can in combination with high-strength metals offer characteristics that cannot be achieved with mono-material parts. One possible example is the combination of locally high-temperature resistance in the metal component with superior weight-related mechanical properties due to the CFRT component. This approach requires a reliable and durable joining technology, which considers the material-specific properties and allows to exploit the full potential of CFRT/metal hybrid parts. A promising approach in the field of CFRT/metal joining is the use of metallic pins, which can be embedded in the locally heated CFRT component to create a form-fitting joint. In the current state of the art, primarily single-pins are investigated and characterized: especially the distinct fiber orientation in the direct pin pressing process is only described for single-pin joints. Behind this background, the present study aims at creating an understanding of the fiber orientation mechanism for multi-pin arrays. Therefore, in the scope of this study, unidirectional reinforced glass fiber/polypropylene samples are joined via direct pin pressing and infrared heating with different 1D and 2D multi-pins arrays with different pin-diameters, spacing and pin distributions. The resulting joint morphology is consequently analyzed using micro-computer-tomography. Based on the performed investigations, a model for the fiber displacement mechanism is proposed, and the first recommendations for the design of fiber-friendly multi-pin joints with unidirectional reinforcements are given. It showed that especially pin-spacing in fiber orientation in dependency of the pin diameter is critical for a fully reconsolidated joint quality, and it is suggested that a pin-offset in the fiber direction is beneficial for a fiber-friendly joining process.

Specific nano- and micro-scale morphologies of composites can affect the resulting optical and UV reflectivity of the materials. One example is “Vantablack®” made from aligned carbon nanotubes (CNTs) with 99.96% absorption. A similar material with CNTs grown on surface-activated aluminum (CNTs/sa-Al) even yielded 99.995% absorption, one order of magnitude higher than Vantablack®. On the other hand, fresh snow reflects 90% or more of the incident electromagnetic radiation with wavelengths between 400 and 1,000 nm. The reflectivity of snow originates from multiple scattering in the porous morphology made of snow grains. Taking these complex morphologies as inspiration, CFRP epoxy composites with different types, sizes, shapes, and amount of nanoparticles are prepared and compared regarding their optical and ultraviolet (UV) reflectivity. Increasing the reflectivity in the near and far UV may be beneficial for the durability of the epoxy composites, but selective higher or lower reflectivity in certain wavelength ranges may also yield tailored visual effects. Results from different processing approaches with selected nanoparticles are presented and discussed.

It is favorable to re-evaluate the seismic hazard for a given territory, since in the course of time new methods are developed and new data are gathered that can enable more sophisticated (physically sound) and reliable assessment of the seismic hazard. Therefore, it is mandatory to re-evaluate the seismic hazard for Kosovo, considering the seismic sources in Kosovo. The data of this article influence the reduction of seismic risk for the territory of Kosovo.

In the present study, the resistance characteristics of Shanghai clayey soil-expanded polystyrene (EPS) mixture have been explored, using unconfined compressive and consolidation and rebound tests. EPS beads were mixed homogenously with clay soil in accordance with different mass ratios of beads to soil, that is, 0, 0.02, and 0.03%. Four particle sizes of EPS were used in the mixtures, that is, 0.5, 1, 3, and 7 mm, to reconstruct the samples. The experimental results indicated that (1) under the condition of unconfined compressive test, with the increase of EPS particle size, the compressive strength of reinforced soil increases significantly, but the compressive strength of reinforced soil decreases compared with the control sample, and it also decreases with high content compared to low EPS content; (2) under the consolidation and rebound test, compression index and rebound index of reinforced soil increased obviously compared with the control sample, but the compression modulus of reinforced soil decreases significantly; (3) in addition, the ductility of reinforced soil decreases with the increase of EPS particle size but increases compared with the control sample. At the same time, the stiffness of reinforced soil is much decreased compared with the control sample. Finally, the cause of deformation characteristics of reinforced soil was explained based on the feature of EPS material and the interaction between soil particles and particles of EPS beads.

Compared with large size foam, pressure microfoam has the characteristics of a good pipeline transportation stability, good jet orientation, strong impact force, and strong ability to capture fine dust, which is more suitable for dust removal. The traditional foam preparation device has the disadvantages of high-pressure loss, poor foaming effect, and foam uniformity. To overcome the above shortcomings, the annular air supply vertical foam preparation device was proposed in the article. The foaming cylinder of the device adopts a vertical design to avoid the influence of uneven distribution of foam caused by gravity; the spiral nozzle is used to evenly spray the foaming liquid on the foaming mesh to increase the contact area between foam and airflow. The stainless steel wire mesh and cotton wire mesh are adopted to improve the reliability and durability of concave foaming mesh. The performance of the new device was obtained by the self-built experimental system. Finally, the field test shows that the conditions of the heading face could fully meet the requirements of the device for pressure water and compressed air, and the produced pressure microfoam can effectively control dust.

The effect of hydrothermal aging on the impact resistance of foam core sandwich panels is studied in this study. The sandwich panels with glass fiber-reinforced skins and polyurethane foam core were fabricated and then were treated with different hydrothermal aging conditions. The moisture absorption characteristic of the composite skins was evaluated. A modified Fickian formulation was proposed to predict the moisture absorption behavior of composite skins. The low-velocity impact resistance of the aged sandwich panels was determined at three different impact energies. The impact responses including contact force, deflection, and dissipated energy of the sandwich panels with and without hydrothermal aging were analyzed. The macroscopic and microscopic damage morphologies were observed by visual inspection and scanning electron microscope methods, respectively. The damage mechanism of the aged panels was revealed. Results indicate that the impact resistance of aged sandwich panels is degraded, and the performance degradation is larger with increasing aging temperature. Compared to the panel without hydrothermal aging, the reduction of the contact force is 35.69%, and the increase of the deflection is 71.43% for the aged panel at 70°C aging temperature. The fiber/matrix interfacial cohesive performance is degraded resulting from the hydrothermal aging.

In this article, a new technology of surface wrapping and strengthening of expandable polystyrene (EPS) beads is proposed. Three wrapping materials including magnesium phosphate cement (MPC), ultra-high performance concrete (UHPC), and water-borne polyurethane (WPU) were evaluated. Four groups of uniaxial compression tests of EPS concrete specimens were conducted: the failure process and the characteristics of the specimens were analyzed; and the complete stress–strain equation is proposed based on these analyses. The research shows that the EPS beads were strengthened by wrapping, and the axial compressive strength of concrete is increased by 50–75%; the concrete with EPS beads wrapped by MPC and WPU has obvious brittleness; the concrete with EPS beads wrapped by UHPC has axial compressive strength close to that of EPS concrete wrapped with MPC and WPU but has a larger ductility coefficient (150%), a larger toughness coefficient (50–90% larger), a higher energy dissipation coefficient (40% larger), and larger residual stress. The proposed stress–strain model is in good agreement with the experimental results, which can accurately describe the stress and deformation characteristics of EPS concrete under uniaxial compression and has good applicability. The discovery of this study provides background knowledge for the structural analysis and design of this kind of concrete; it provides a basis for selecting EPS concrete as structural materials.