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The axial compressive bearing capacity, failure modes, and failure mechanisms of carbon fiber-reinforced aluminum laminate (CARALL) columns with single-channel cross sections were studied in detail. In this study, two types of short CARALL specimens with a 5/4 configuration were first fabricated using 2024-T3 aluminum alloy and different fiber orientations ([0°/90°/0°]3, [45°/0°/−45°]3) via a pressure-molding thermal-curing forming process. The short CARALL columns were then subjected to static loading tests to determine their axial compressive behaviors in terms of ultimate bearing capacity and failure modes. Thereafter, the user-defined FORTRAN subroutine VUMAT, which is based on ABAQUS, was used to investigate the failure mechanism of the proposed CARALL columns. Meanwhile, based on the classic laminated panel mechanics theory, a theoretical method was proposed to predict the safe bearing capacity of the designed compressive CARALL columns. The results indicated that the ultimate failure of both types of short CARALL columns was a strength failure caused by the delamination of the layers. When the short CARALL columns were subjected to an axial compressive load, the fiber spread angle of the carbon fiber-reinforced polymer prepregs in the laminate panels had a significant influence on the resistance to interlaminar delamination. A smaller fiber layer angle resulted in greater resistance to interlaminar delamination. Setting a certain number of fiber layers with angles between 0° and 45° could increase the toughness of the compression column member against interlaminar shear delamination at the initial stage. Comparisons of the experimental, numerical, and theoretical results demonstrated good agreement, indicating that the proposed theoretical method is feasible for predicting the safe bearing capacity of CARALL columns with a single-channel cross section and can be applied to the design of compressive laminate pillar components.

In the numerical simulation of the macroscopic flow of the concrete, it can optimize the performance indicators of the screw conveyor and improve the uniformity of the material to be discharged in the batch production. The discrete element method is effective. The accuracy of physical parameters of this method is a key issue for the reliability of the simulation results of concrete. In this study, we measured the parameters describing the interaction between gravel, mortar, as well as between these two materials and the wall (steel). The experimentally determined parameters include the particle density, size, shape, coefficient of restitution, coefficients of static, and rolling friction. The cohesion coefficient of mortar particles for batch time was obtained by comparing the spread diameter and flow time in V-funnel experiments and simulation. After these calibration steps, the DEM parameters were validated by comparison of the mass flow rate and driving power by the batch production of screw conveying in simulations and experiments. The calculated results are proved to be close to the experimental data, which demonstrates that the measured DEM parameters are of sufficient accuracy to be used in the simulation of concrete flow performance (mass flow rate, energy consumption) in the screw conveyors.

Fiber reinforced rubber pipes are widely used to transport fluid at locations requiring flexible connections in pipeline systems. The spherical self-balancing fiber reinforced rubber pipes with low stiffness are drawing attention because of their vibration suppression performance under high internal pressure. In this paper, a theoretical model is proposed to calculate the axial stiffness and lateral stiffness of spherical self-balancing fiber reinforced rubber pipes. The inhomogeneous anisotropy of the reinforced layer and the nonlinear stress-strain relationship of the reinforced fiber are considered in the model. The accuracy of the model is verified by experimental results. Theoretical calculation finds that both the axial and lateral stiffness are influenced significantly by the key structural parameters of the pipe (the axial length, the circumferential radius at the end, the meridional radius, and the initial winding angle). The stiffness can be reduced remarkably with optimal meridional radius and initial winding angle, without any side effect on the self-balance of the pipe. The investigation methods and results presented in this paper will provide guidance for design of fiber reinforced rubber pipes in the future.

The aim of the study is to develop and investigate the suitability of thermoplastic composites for underwater applications. PA6/PP/PP-g-MA (70 wt%/30 wt%/3 phr) blend is used as a novel matrix to synthesize UDCF composites with balanced strength and toughness even in humid conditions. This novel matrix has around 60% lower water absorption capacity compared to PA6. Short carbon fibres (SCF) and unidirectional carbon fibre fabric (UDCF with 12K rovings) are used as reinforcements. X-ray CT data of injection-molded SCF composites revealed good wetting. However, in the case of compression-molded UDCF composites, a few unwetted zones were found. Comparing dry and wet samples, wet-matrix, wet-SCF composite and wet-UDCF composites had 40, 15, and 25% reduction in their tensile strengths, respectively. However, the impact strength of wet-matrix and wet-UDCF composites increased by 67 and 61%, respectively. Hence, SCF composites having a wet tensile strength of 46 MPa can be used in preparing underwater components due to the low number of interfacial voids. UDCF composites having more interfacial voids are recommended for humid conditions wherein the wet impact strength (11.4 J) and wet tensile strength (266 MPa) are the main criteria.

Composite structures (SiC/UHMWPE/TC4; SiC/TC4/UHMWPE) were designed using silicon carbide (SiC)ceramics, ultra-high-molecular-weight polyethylene (UHMWPE) laminate, and titanium alloys (TC4s). Penetration experiments and numerical simulations were carried out to study the anti-penetration mechanism and energy characteristics of the composite structures, and the microstructure of the TC4 was analyzed. The results show that the two composite structures designed have advantages in reducing mass and thickness. The energy proportion of the TC4 is the largest among the three materials, which mainly determines the anti-penetration performance. The microstructure of the TC4 in composite structure I shows rough edges of bullet holes, a large number of adiabatic shear bands (ASBs), ASB bends and bifurcates, and many cracks, which lead to spalling damage of the TC4. The microstructure of the TC4 in composite structure II shows flat edges of bullet holes, several straight ASBs, and no cracks, which leads to brittle fragmentation. The initiation, expansion, combination of ASBs and cracks lead to more energy consumption. Therefore, the combination form of composite structure I can give full play the energy dissipation mechanism of the TC4 and has better anti-penetration performance than composite structure II.

The joint roughness has an influence on the uniaxial compressive strength (UCS) and characteristic strength of the rock, but the relationship of the influence is yet to be obtained. In this article, the influence of the size of the rock with rough joints on the UCS and the influence of the size effect of roughness on the UCS are studied by establishing 11 sets of numerical simulation schemes, a total of 30 working conditions. The stress–strain curve law of rocks with different roughness and sizes is analyzed, and the relationship between UCS and the size of rock with rough joints, joint roughness coefficient (JRC), is respectively proposed. Mathematical models of rock characteristic size of UCS, characteristic strength of the rock, and JRC are established, respectively.

Hybrid fiber composites are widely used to improve the anti-penetration performance. Carbon/Kevlar hybrid composites are used in aircrafts and safety devices, thanks to the strong toughness of Kevlar fibers and high strength of carbon fibers. In the present work, the contact force of hybrid composites under oblique impact is derived. The viscoelastic constitutive model of Kevlar layer is investigated and the dissipation energies of composites for different high velocity oblique impacts are simulated. The results show that hybrid composites have good bullet-proof performance, the contact forces are fluctuant in short time and the frictional dissipation energy allows us to prevent penetration.

A new model based on continuum damage mechanics is proposed to predict the fatigue life of 2.5D woven composites. First, a full-cell model reflecting the real microstructure of 2.5D woven composites is established in ANSYS. Subsequently, three independent damage variables are defined in the framework of the composite micromechanics to establish the component constitutive relations associated with damage. The strain energy density release rate and damage evolution equations for the matrix, fiber in yarns, and matrix in yarns are derived. Finally, the proposed model is implemented for fatigue life prediction and damage evolution analysis of 2.5D woven composites at 20 and 180°C. The results show that the numerical results are in good agreement with the relevant experimental results.

This article discusses the influence of fiber types, including polyvinyl alcohol (PVA) fiber, polyethylene (PE) fiber, and steel fiber (SF), on the compressive strength, flexural strength, bending toughness, and tensile ductility of lightweight cement-based composites. The fiber dispersion and the microscopic morphology were assessed using fluorescence and scanning electron microscopes. The result showed that the SFs had the best effect in enhancing the compressive and flexural strengths of lightweight cement-based composites, and its compressive and flexural strengths reached 88.9 and 17.6 MPa, respectively. Compared with the PVA and the SFs, the PE fiber had the most significant effect on the ductility of lightweight cement-based composites; the tensile strength and the ultimate tensile strain were 3.29 MPa and 2.56%, respectively, due to a very high bridging capability provided by the PE fiber. A large amount of hydration products adhered to the surface of the PVA fiber, which improved the adhesion between the cement matrix and the PVA fiber and caused the rupture of most of the PVA fiber. Overall, lightweight toughness cement-based composites containing PVA and PE fibers have a good deformability, which can meet the needs of construction and transportation engineering applications.

To meet the high-precision needs of conductive ink in the field of microelectronic circuit printing, nano silver-coated graphene oxide (GO) composites were prepared as the conductive functional unit of the composites. The results show that compatibility of the GO grafted with ethylene glycol diglycidyl ether is better in the organic matrix than in the inorganic solvents. The nano silver particles attached to the surface of the grafted GO are evenly distributed and uniform in size. Moreover, the conductivity of grafted GO coated with silver particle composites is effectively improved. The composite conductivity is higher than 108 S/m, which is close to the electrical conductivity of silver.

Carbon fiber reinforced polymer (CFRP) is widely used in high-tech industries because of its interesting characteristics and properties. This material presents good strength and stiffness, relatively low density, high damping ability, good dimensional stability, and good corrosion resistance. However, the machinability of composite materials is complex because of the matrix/fiber interface, being a challenging machining material. The CFRP milling process is still necessary to meet dimensional tolerances, the manufacture of difficult-to-mold features like pockets or complexes advance surfaces, finish the edges of laminated composites, or drill holes for the assembly of the components. Besides, the demand for low-cost, reconfigurable manufacturing systems of the industry demonstrates that the application of industrial robots (IRs) in the CFRP milling process becomes an alternative for providing automation and flexibility. Therefore, the objective of this work is to evaluate the performance of the low payload IR KUKA KR60 HA in a milling experiment of CFRP, which indicates its potential application as an alternative to milling process. Furthermore, the influence of the cutting tool geometry as well as the cutting parameters in the machining behavior with IRs is evaluated.

The accurate characterization of fabrics used in vacuum assisted resin transfer molding (VARTM) is essential in order to model the flow through these porous preforms. A wide range of these fabrics are available for composite manufacturing through VARTM and thus brings about a need to opt a methodology which characterizes the in-plane permeability of these preforms. These permeability values can then be used in simulations that can track the flow front progression and mold filling time. This work identifies the permeability of an E-glass fabric based on Darcy's law. Woven fabric having areal weight of 200 grams per square meter (gsm) is under consideration. The experiments are conducted at constant pressure conditions using 2D Radial flow method. Stereo microscopy of the preform material is done for detailed study of the weaving pattern. It is concluded that plain woven fabric exhibits anisotropic behavior when tested for in-plane permeability. Permeability is found to be higher in a direction which offers more interspacing between adjacent fibers threads causing more resin to flow in this direction.

This study aims to investigate the role of nano TiO2 in modifying the characteristics of Shanghai clayey silt – alluvial soil in Yangtze river estuary. The Shanghai clayey silt is first mixed with nano TiO2 with different size group and content before it is made to undergo liquid and plastic limit tests, standard Proctor compaction tests, and acid-resistant tests. The results show that nano TiO2 can substantially increase the liquid limit and plastic limit of TiO2-treated clayey silt, but can decrease the plasticity index of it to some degree. The result from standard Proctor compaction tests shows that the maximum dry bulk density (MBD) decreases and the optimum water content (OWC) increases compared with untreated samples. Acid-resistance of sample is significantly increased after being treated by nano titanium dioxide. The data provided by this study can be used for not only the soil and water conservation, but also for soil improvement, diversity of vegetables and animals, amelioration of crop land, as well as sustainable development.

Metal-composite laminates and joints are applied in aircraft manufacturing and maintenance (repairing) using aluminum alloys (AA) and glass fiber-reinforced polymer (GFRP). In these applications, drilling has a prominent place due to its vast application in aeronautical structures’ mechanical joints. Thus, this study presents the influence of uncoated carbide drills (85C, 86C, H10N), cutting speeds (v c = 20, 40, and 60 m min−1), and feed rates (f = 0.05, 0.15, and 0.25 mm rev−1) on delamination factor, thrust force ( F t {F}_{\text{t}} ), and burr formation in dry drilling metal-composite laminates and joints (AA2024/GFRP/AA2024). Experiments were performed, analyzed, and optimized using the Box–Behnken statistical design. Microscopic digital images for delamination evaluation, piezoelectric dynamometer for thrust force acquisition, and burr analysis were considered. The major finding was that the thrust force during drilling depends significantly on the feed rate. Another significant factor was the influence of the drill type (combined or not with feed rate). In fact, it was verified that the feed rate and the drill type were the most significant parameters on the delamination factor, while the feed rate was the most relevant on thrust force. The cutting speed did not affect significantly thrust force and delamination factor at exit ( F da S ) \hspace{.25em}({F}_{{\text{da}}_{\text{S}}}) . However, the combination f × v c was significant in delamination factor at entrance ( F da E ) \text{ }({F}_{{\text{da}}_{\text{E}}}) . Based on the optimized input parameters, they presented lower values for delamination factors ( F da E = 1.18 {F}_{{\text{da}}_{\text{E}}}=1.18 and F da S = 1.33 {F}_{{\text{da}}_{\text{S}}}=\hspace{.25em}1.33 ) and thrust force ( F t = 67.3 N {F}_{\text{t}}=67.3\hspace{.5em}\text{N} ). These values were obtained by drilling the metal-composite laminates with 85C-tool, 0.05 mm rev−1 feed rate, and 20 m min−1 cutting speed. However, the burrs at the hole output of AA2024 were considered unsatisfactory for this specific condition, which implies additional investigation.

In this article, the parametric model for the stiffness characteristic and burst pressure of cord-reinforced air spring with winding formation is developed. Based on the non-geostrophic winding model and the assumption of cord cross-stability, the cord winding trajectory model of the capsule is established. Then, the anisotropic and nonlinear mechanics model of the capsule with complex cord winding trajectory variation characteristics is constructed by the classical thin-shell theory. The capsule state vector is solved by the extended homogeneous capacity precision integration method. Due to the complex coupling relationship between the capsule state vector and the internal air pressure, the stiffness characteristic is solved by the iterative integration method. The burst pressure of the air spring is solved by the Tsai–Hill strength theory. Eventually, the accuracy and reliability of the proposed method are verified by the experimental results. The effects of the material properties, winding parameters, and geometric structure parameters on stiffness characteristics and burst pressure are discussed. The results of this article provide an important theoretical basis for the performance design of cord-reinforced air springs with winding formation.

3D-printing finds increasing applications including the dental implant. We report in this study a nicely printed and then cured composite consisting of nano-ceramic and photosensitive resin, targeting oral prosthesis application. The results show that the 3D-printed material has good geometry accuracy and satisfactory hardness, justifying its potential as an advanced manufacturing methodology for future dentistry.

The recycled brick micropowder was formed after crushing and ball milling and waste clay bricks have great potential activity. It can replace some percentage of cement in the preparation of concrete through activation effects of excitation, and thus, reutilization of waste products is the objective of this study. This study analyzed the activation effects of mechanical excitation, chemical excitation, and high-temperature excitation on the activity of regenerated brick powder. The correlation between different excitation methods and the activity index was fitted, and the microstructure and mechanism of action of the material were analyzed and revealed using SEM and XRD techniques. The results show that after using mechanical excitation, chemical excitation, and high-temperature excitation to activate the brick powder, the activity index of the material was improved to varying degrees, and there is a good correlation between different excitation modes and the activity index. The study shows that the 45 min mechanical excitation of ball milling and the high-temperature excitation of 800 have better effects, with the highest activity index reaching 71%, and the highest activity index in the chemical excitation mode is 65%. Considering the excitation effect, energy consumption, economy, and practical operation feasibility, it is recommended to use the ball milling 45 min excitation method as the best activation method for the recycled brick micropowder.

Self-Consolidating Concrete (SCC) has also brittle characteristics. This is unacceptable for any construction industry. The addition of fibers is one of the most common methods to enhance the tensile strength of concrete. Fiber controls the cracking phenomena and enhances the energy absorption capability of the concrete. On the other hand, the addition of fibers has a negative impact on the workability of fresh concrete. In this paper, a detailed study on the influence of Propylene fibers (PP) on the fresh properties of SCC was carried out. PFs were added into concrete mixes in a proportion of 1.0%, 2.0%, 3.0%, and 4.0% by weight of cement to offset its undesirable brittle nature and enhance its tensile strength. The fresh characteristics were evaluated based on its passing ability, flowability using, Slump flow, Slump T50 Spread time, L-Box and V-funnel tests as well as mechanical performance (compressive and split tensile strength) were also evaluated at 7,14 and 28 days curing. Test results indicate that the passing and filling ability decreased as the substitution ratio of PP increased. Besides, the test result indicates that strength was increased up to 2.0% addition of PP and then decrease gradually.

This study experimentally investigates the effect of the opening configuration on the buckling stability and bearing performance of a structural beam web used in a commercial aircraft made of composite materials. The buckling and strength analyses on three opening configurations (circular, oblong, and rhombic) were carried out using test samples with identical web surface size. It is found that the rhombic opening has the minimum effect on the buckling stability and strength of the structure. To compensate for the effect of the opening, two reinforcement methods, using reinforcement rib and thickening the sample, were also investigated in this study. It is concluded that thickening the sample can more effectively improve the buckling stability and strength performance of beam web structure and hence has relatively higher structural reinforcement efficiency.

Fine aggregates of construction waste and fly ash were selected as additives to modify the characteristics of Shanghai clayey soil as a composite. The laboratory tests on consistency index, maximum dry density, and unconfined compressive strength were carried out mainly for the purpose of comparing the modifying effect on the composite from fine aggregates of construction waste with that from fly ash. It is mainly concluded from test results that the liquid and plastic limit of the composites increase with the content of two additives. But their maximum dry density all decreases with the additive content. However, fine aggregates of construction waste can increase the optimum water content of the composites, while fly ash on the contrary. Finally, although the two additive all can increase the unconfined compressive strength of composites, fly ash has better effect. The current conclusions are also compared with previous studies, which indicates that the current research results are not completely the same as those from other researchers.

The paper corrugation tube is an innovative kind of energy absorbing structure and shock absorber which can play an important role on the cushioning energy absorption for airdrop equipments and transportation packaging. The deformation characteristics and failure modes of the regular triangle, quadrangle, pentagon and hexagon paper corrugation tubes were comparatively studied by a series of axial static compression experiments, the cushioning energy absorption was evaluated by the seven characteristic parameters (e.g. initial peak force, mean crush force, total energy absorption, specific energy absorption, crush force efficiency, unit area energy absorption and stroke efficiency), and the influences of tube direction, cross-sectional shape, tube length and compression rate on failure modes and cushioning energy absorption were analyzed and compared. These researches showed that the tubes along X direction only have the accordion deformation mode, yet the tubes along Y direction have four deformation modes including steady state progressive buckling, Euler buckling, angular tear and transverse shear. For the paper corrugation tubes along Y direction, the cross-sectional shape has obvious influence on the cushioning energy absorption of structures, and the specific energy absorption and unit area energy absorption of regular triangle and pentagon tubes are better than those of the tubes with regular quadrilateral and hexagonal cross-section at compression rates of 12 and 48mm/min. The tube length of 150 mm or compression rate of 72 mm/min would cause the increase of contribution proportion of non-ideal deformation mode and the decrease of cushioning properties. The paper corrugation tubes along X direction have more stable and controllable deformation mode, yet the paper corrugation tubes along Y direction have better cushioning energy absorption.

In this paper, a new method is developed to investigate the anti-penetration performance of the steel/nylon sandwich plate, which incorporates experimental method with numerical simulation. Constitutive parameters of the steel/nylon sandwich plate are measured by the Hopkinson Pressure Bar, and LS-DYNA is applied to simulate the penetration process of projectiles into the sandwich plate. The dynamic response, failure modes and energy absorption coefficients are obtained, and the penetration tests are conducted to verify the numerical method. Results show: results obtained by experimental and numerical methods have very high agreement, which demonstrates that the method proposed can be applicable for predicting the anti-penetration performance of the sandwich plate.

In this study, a kind of structural gradient metal hollow spheres composites (SG-MHSCs) were fabricated using two kinds of 316L stainless steel hollow spheres with different diameters and A356 aluminum through the casting method. Then the density of the SG-MHSCs was measured by the direct measurement; the microstructure of the SG-MHSCs was characterized by the Scanning Electron Microscope. Meanwhile, the acoustic performance of MHSCs was tested by the impedance tube, and the sound absorption and insulation mechanism SG-MHSCs were discussed and analyzed.

As the wind turbine size gets larger, the optimal design of blades, which is a major source of energy for the wind turbines and also the cause of loads, is becoming more important than anything else. Therefore, reducing the load on the blade should be the top priority in designing a blade. In this article, we studied the vibration control of the stiffened wind blades subjected to a wind load with piezoelectric sensors and actuators to mitigate fluctuations in loading and adding damping to the blade. The model is a laminated composite blade with a shear web and the PZT piezomaterial layers embedded on the top and bottom surfaces act as a sensor and actuator, respectively. A uniformly distributed external wind load is assumed over the entire plate surface for simplicity. The first-order shear deformation (FSDT) theory is adopted, and Hamilton’s principle is used to derive the finite element equation of motion. The modal superposition technique and the Newmark- β \beta method are used in numerical analysis to calculate the dynamic response. Using the constant gain negative velocity feedback control algorithm, vibration characteristics and transient responses are compared. Furthermore, vibration control at various locations of the shear webs subjected to an external load is discussed in detail. Through various calculation results performed in this study, this article proposes a method of designing a blade that can reduce the load by actively responding to the external load acting on the wind turbine blade.

In this article, mode II fracture toughness ( G IIc {G}_{\text{IIc}} ) of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid aging is studied at two different temperatures (25 and 90°C). Specimens were manufactured using the hand lay-up method with the [ 0 ] 20 {{[}0]}_{20} stacking sequence. To study the effects of environmental conditions, samples were exposed to 30 wt% sulfuric acid at room temperature (25°C) for 0, 1, 2, 4, and 8 weeks. Some samples were also placed in the same solution but at 90°C and for 3, 6, 9, and 12 days to determine the interlaminar fracture toughness at different aging conditions. Fracture tests were conducted using end notched flexure (ENF) specimens according to ASTM D7905. The results obtained at 25°C showed that mode II fracture toughness increases for the first 2 weeks of aging and then it decreases for the last 8 weeks. It was also found that the flexural modulus changes with the same trend. Based on the results of the specimens aged at 90°C, a sharp drop in fracture toughness and flexural modulus with a significant decrease in maximum load have been observed due to the aging. Finite element simulations were performed using the cohesive zone model (CZM) to predict the global response of the tested beams.

In this study, the effects of steel fibers on the mechanical properties of the geopolymer concrete – compressive, splitting tensile, and flexural strength; compressive elastic modulus; and fracture properties – were evaluated. Milling steel fibers were incorporated into the geopolymer concrete, and the volume fraction of the steel fibers was varied from 0 to 2.5%. Fly ash and metakaolin were chosen as the geopolymer precursors. Fracture parameters – critical effective crack length, initial fracture toughness, and unstable fracture toughness – were measured by a three-point bending test. The results indicated that all the mechanical properties of the geopolymer concrete are remarkably improved by the steel fibers with the optimum dosage. When the steel fiber content was under 2%, the cubic and axial compressive strength and the compressive elastic modulus increased. The inclusion of 2% steel fibers enhanced the cubic and axial compressive strength and the compressive elastic modulus by 27.6, 23.7, and 47.7%, respectively. When the steel fiber content exceeded 2%, the cubic and axial compressive strength and the compressive elastic modulus decreased, having values still higher than those of the geopolymer concrete without steel fibers. The splitting tensile strength and flexural strength of the concrete were enhanced with increasing steel fiber content. When the steel fiber content was 2.5%, the increment of the splitting tensile strength was 39.8%, whereas that of the flexural strength was 134.6%. The addition of steel fibers effectively improved the fracture toughness of the geopolymer concrete. With 2.5% steel fibers, the initial fracture toughness had an increase of 27.8%, and the unstable fracture toughness increased by 12.74 times compared to that of the geopolymer concrete without the steel fibers.

The undoped YVO4 and Ce3+-doped YVO4 single crystals have been successfully grown by the Czochralski method in a medium frequency induction furnace. The X-ray diffraction patterns testified that all samples exhibited the pure tetragonal YVO4 crystalline phase without any parasitic phases. The optical properties of Ce3+-doped YVO4 single crystals with different doping concentrations were investigated via a combination of absorption, emission, and excitation spectra. Dependence of luminescence and absorption intensity on Ce3+ doping concentration was discussed at different excitation wavelengths. The typical transitions of Ce3+ ions and the unusual intrinsic luminescent phenomena of VO 4 3 − {\text{VO}}_{4}^{3-} groups were observed and investigated in Ce3+-doped YVO4 crystals. More attentions were paid to ascertaining the corresponding transition states, analyzing luminescent mechanism, and revealing the energy transfer from VO 4 3 − {\text{VO}}_{4}^{3-} to Ce3+ ions. In addition, the CIE chromaticity coordinates and correlated color temperature were calculated on a basis of emission spectra under different excitation wavelengths.

In this study an automated composite layup end effector is presented which is the first to be able to find defects in real time during layup using tactile shape sensing. Based around an existing sensor concept developed by the Bristol Robot Laboratory known as the ‘TacTip’, a new end effector is developed, replacing the soft gel core of the original sensor was replaced by a much firmer elastomer, enabling it to apply up to 400N of compaction force. In this paper it is shown to successfully detect typical defects such as wrinkles, foreign objects, layup errors or incorrect material types while simultaneously compacting preimpregnated composite materials over complex mould shapes.

Two categories of GFRP specimens, in nominal diameters of 11.2 mm and 15.6 mm respectively, made of E-glass fibers and a vinylester resin were immersed in alkaline solution, saline solution and tap water solution at room temperature. The mechanical and durability properties of tested GFRP bar specimens were determined through direct tensile test and short-beam shear test after exposure to aggressive solutions for different days. The obtained results indicated that for all tested GFRP bar specimens the failure modes of fiber rupture in the tensile test and horizontal cracking in the short-beam shear test would not obviously change with the increasing of exposure period. However, the impact of immersion solutions on the durability degradation of mechanical properties of GFRP bars appeared in the ultimate strength and displacement at failure, and at room temperature the alkaline solution had a greater impact than another two solutions. Under the same exposure conditions, the resistance to the strength degradation of the GFRP bars with a larger diameter was better than that of the smaller GFRP bars. The comparison results indicated that the strength degradation trend of conditioned GFRP bars presented in our study was basically in agreement with the data given in previous studies.

In order to prepare polyurethane–polysiloxane block copolymers, α,ω-hydroxyalkyl polysiloxanes with methacrylate side chain and α,ω-bis(2-methyl-3-hydroxypropyl)polymethyl(2-methyl-methylpropanoate) siloxanes, were synthesized and characterized in this study. The syntheses process included hydroxyl protection, hydrosilylation, deprotection, and ring-opening equilibrium reactions. The intermediates and target products were characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance methods. The characterization results showed that each step was successfully carried out in all the cases. Then the waterborne polyurethane–polysiloxane block copolymers were prepared via step-growth polymerization. The properties of the block copolymer films were characterized by thermal gravimetric analysis, differential scanning calorimetry, and dynamic thermomechanical analysis methods in detail. The experimental results showed that the block introduction of hydroxyalkyl polysiloxane could reduce the water absorption of waterborne polyurethane from 62 to 11%, and significantly improve the water resistance of polyurethane. With the introduction of polysiloxane, the tensile strength decreased and the elongation at break increased. At the same time, with the increase of the polysiloxane content, the glass transition temperature of the soft segment decreased to −56.4°C and the thermal decomposition temperature increased to 300°C. The results revealed that the introduction of polysiloxane could effectively improve the comprehensive performance of polyurethane–polysiloxane block copolymer films.

Nano-Al2O3 dispersion-strengthened Cu20W composite was fabricated by vacuum hot-pressing sintering process. The electrical conductivity, relative density, and Brinell hardness were tested, respectively. The gleeble-1500D thermomechanical simulator was used to conduct isothermal compression with strain rates ranging from 0.001 to 10 s−1 and the temperatures ranging from 650 to 950°C. The microstructure of the Cu–Al2O3/20W composite was observed using an optical microscope and a transmission electron microscope, and the true stress–strain curves were analyzed. In addition, the influence of the nano-Al2O3 and tungsten on the thermal deformation process of the composite was analyzed. The relationship and interaction among work hardening, dynamic recovery, and dynamic recrystallization were illustrated. The results show that nano-Al2O3 particles pin dislocations and inhibit dynamic recovery and dynamic recrystallization. Consequently, the Cu–Al2O3/20W composite has typical dynamic recovery characteristics. Hence, the Cu–Al2O3/20W composite possesses outstanding high-temperature performance. The optimal processing domain of the Cu–Al2O3/20W composite ranged from 760 to 950°C with strain rates ranging from 0.01 to 0.1 s−1. Furthermore, the constitutive equation of the Cu–Al2O3/20W composite is established, and the activation energy is 155.069 kJ mol−1.

Geological conditions play a decisive role in the stability of arch dam engineering, and the asymmetric geological conditions of the abutment have a very negative impact on the safety of the arch dam. This article takes Lizhou arch dam as the research object, and determines that the arch dam is preliminarily affected by the geological asymmetric characteristics. Through the geomechanical model test method, the overload failure test of the Lizhou arch dam was carried out, and the resistance body, the instability deformation of the structural plane of the two dam abutments, and the influence of each structural plane on the dam body are obtained, and the safety factor is determined. According to the test results under the condition of asymmetric foundation of arch dam, for the structural plane which affects the geological asymmetry of the arch dam, the corresponding reinforcement measures are carried out. The feasibility of the reinforcement scheme is verified by the finite element method, and the safety factor after reinforcement is obtained. According to the results, it is suggested that some engineering measures can be taken to reduce the geological asymmetry between the two banks and ensure the safe and stable operation of the arch dam in the future.

Composite materials are used in many industries. Their mechanical and physical properties as well as their low weight make them suitable for use in many constructions. Their wide application generates a problem with their disposal. Therefore, it is necessary to design new materials based on waste from polyester–glass laminates in order to introduce a closed circuit in the composite production process. The article presents research aimed at determining solid material composites with polyester–glass recyclate, in order to use these materials for modeling the structure. The aim of this study was to determine the effect of the addition of recyclate to the polyester–glass composite on the deformation and the value of the Poisson number of the material. During the study, samples from composites with the addition of polyester–glass recyclate were used. Samples made in accordance with the standard for plastics PN-EN ISO 527-4_2000P were subjected to static tensile test on a universal testing machine, with variable load parameters. During the test, the longitudinal and transverse elongations of the samples were measured using a strain gauge measuring system. On the basis of the measurements, the values of Poisson numbers were determined, which allowed for a preliminary assessment of the impact of the recyclate content in the composite on its deformability.

In this paper, the effects of multiwalled carbon nanotubes (MWCNTs) on the mechanical and damping properties of ultra-high performance concrete (UHPC) were investigated. The results show that the proper amount of MWCNTs can improve mechanical properties as well as the damping properties. For the mechanical properties, the compressive strength and flexural strength of the specimens increased with the increase of MWCNTs content in the range of 0~0.05% (mass ratio to cement). However, when the content of MWCNTs was more than 0.05wt.%, the mechanical properties of UHPC could not be improved continually because too many MWCNTs were difficult to disperse and agglomerated easily in UHPC. Similar laws also have been found for the damping property of UHPC. The loss factor of UHPC increased with the increase of MWCNTs content in the range of 0 ~ 0.05%. The incorporation of MWCNTs would introduce a large number of interfaces into UHPC, the friction and slip between interfaces were the main reasons for the improvement of the damping property of UHPC. However, when the content of MWCNTs was more than 0.05%, it was difficult to disperse effectively. As a result, the overall energy consumption efficiency of MWCNTs was decreased.

The present study addresses the mechanical behavior of polypropylene self-reinforced composites (SRC’s) considering polymeric structural changes after cutting. Self-reinforced polypropylene composite is fabricated using the HOT compaction method by maintaining the processing temperature at 164∘C. Conventional and unconventional cutting methods were used to cut the samples of standard dimensions. FTIR images revealed the formation of C=C, C-F, Halogen bonds after AWJ cutting initiated a decrease in the surface roughness value to 4.5μm (R a ). SEM analysis is performed to analyse structural integrity and damage of SRC’s. Structural changes formation after AWJ cutting leads to improve the ultimate tensile strength of the laminate by 20% compared to conventional cut samples. A similar trend is noticed for flexural properties and Shore –D hardness values for the SRC composite laminate correlated to polymeric changes with Conventional cutting due to the formation of C-N bond is observed after Laser cutting.

Electrochemical discharge machining (ECDM) is a well-known process for machining of particulate reinforced metal matrix composites (MMCs). However, ECDM process suffers several drawbacks such as the lower material removal rate (MRR), high risks of tool wear rate (TWR) and relatively poor surface quality, etc. This study proposes a kind of electrochemical discharge grinding machining (ECDGM) method which employs a special shaped tool electrode. During the process, not only the can the hybrid action of electrochemical dissolution, spark erosion, and abrasive grinding improve the performance of machining MMCs, but also the special shaped of the tool electrode can be used to discharge the machined debris. And thus a higher machining efficiency and lower TWR can be obtained. The performance of developed process was conducted on machining of SiC particulate reinforced aluminum workpiece. The role of peak curre+nt, pulse duration, duty cycle, rotary speed and abrasive grit size has been investigated on MMR and TWR using the nonabrasive round electrode, abrasive round electrode, and abrasive shaped electrode respectively. The experimental results showed that using the shaped abrasive electrode for machining MMCs can achieve a higher MRR and lower TWR, as compared to the non-abrasive round electrode, abrasive round electrode. Besides, the orthogonal method was employed to analyze the relative importance of the machining parameters on MRR and TWR, it has been observed that MRR is affected by the processing parameters following the order of rotary speed > peak current > duty cycle > pulse duration, and TWR is following the order of peak current > duty cycle > pulse duration > rotary speed.

In this paper, multiscale acoustic emission (AE) signal analysis was applied to acoustic emission data processing to classify the AE signals produced during the tensile process of C/SiC mini-composites. An established unsupervised clustering algorithm was provided to classify an unknown set of AE data into reasonable classes. In order to correctly match the obtained classes of the AE signals with the damage mode of the sample, three scales of materials were involved. Single fiber tensile test and fiber bundle tensile test were firstly performed to achieve the characteristics of AE signal of fiber fracture. Parameter analysis and waveform analysis were added to extract the different features of each class of signals in the In-situ tensile test of C/SiC mini-composite. The change of strain field on the sample surface analyzed by DIC (Digital Image Correlation) revealed the corresponding relationship between matrix cracking and AE signals. Microscopic examinationwas used to correlate the clusters to the damage mode. By analyzing the evolution process of signal activation for each class against the load, it also provided a reliable basis for the correlation between the obtained classes of the AE signals and the damage mechanism of the material.

The article outlines the methods, which has designated Young’s Modulus and Poisson’s Ratio of deformable cement adhesives. These indicators are necessary for the strength calculation of the lightweight floor systems (LFS), that do not require screeds with and without heating, using the finite element method. It was noticed that the diagrams of the dependence the stress on deformation in deformable cement adhesives are similar to the model of the ‘Madrid parabola’ used in testing concrete and cement mortar. In order to determine that the theory of ‘Madrid parabola’ is correct, calculations were performed using the least amount of squares approximation method. The data of the experimental studies combined with the formula calculations, allowed the study to achieve a reliable result, together to determine whether the theory of relative approximation is correct or not. All these actions have allowed determining the smallest deformations εc 2 in deformable cement adhesives type C2S1 and C2S2 and their compressive strength. Thanks, these two methods (experimental and calculation) the functions describing deformable cement adhesives are defined. They were named S1 and S2 Evola and can be used by designers and producers of floor systems that do not require screeds.

The paper corrugation tube is an attractive and innovative mode of cushioning protection and energy absorption for the general protection and packaging technology of military and civil products. The aims of this paper focus on the dynamic compression characteristics of four kinds of regular polygonal paper corrugation tubes under the conditions of axial drop impacts, and the influence rules of structural parameters and load parameters on the dynamic cushioning energy absorption. The results show that, the tube direction has a crucial effect on the deformation mode of the paper corrugation tubes, the deformation of X-direction paper corrugation tubes has a stable accordion mode, but that of Y-direction paper corrugation tubes is a mixture of steady progressive buckling and other non-ideal modes. The X-direction paper corrugation tubes have lower peak stress, stable and controllable deformation mode with multiple folds, and higher total energy absorption, unit area energy absorption, specific energy absorption and stroke efficiency than the Y-direction paper corrugation tubes. Moreover, the change of cross-section shape of X-direction paper corrugation tubes has no obvious influence on the total energy absorption, while the total energy absorption of Y-direction paper corrugation tube obviously rises with the increase of the number of cross-section edges of the tubes, but the unit area energy absorption, specific energy absorption and stroke efficiency decrease with the increase of the number of cross-section edges of the tubes. Moreover, the increase of the number of cross-section edges of the tubes made the total energy absorption of Y-direction tubes rise, while the total energy absorption of X-direction tubes has no obvious change. But the unit area energy absorption, specific energy absorption and stroke efficiency decrease with the increase of the number of cross-section edges of the tubes. Furthermore, the tube length, impact block mass and impact energy have also important influence on the cushioning energy absorption of the paper corrugation tubes under axial drop impact.

The use of multi-walled carbon nanotubes (MWC-NTs), as excellent mechanical and conductive fibers, for making self-sensing cementitious composites has attracted great interest. However, few researches have focused on the durability of mortar with MWCNTs. This paper attempts to explore the corrosion of embedded steel rebar in cement mortar with different contents of MWC-NTs. Tests for compressive strength, chloride migration coefficient, conductivity, and corrosion behaviors of MWCNT-cement mortar were carried out. The results show that the addition of MWCNTs to the cement mortar accelerated the development of the steel corrosion under chloride environment. The migration behavior of chlorine ions and steel corrosion rate were related to the carbon nanotube content. The increase in carbon nanotube content resulted in higher steel corrosion intensities. Moreover, the rates of chloride transport into the mortar increased with the nanotube content under both accelerated and natural chloride conditions.

Al3Ti/ADC12 composite was synthesized in situ using Al-fluoride potassium titanate (K2TiF6) as the reaction system and an ultrasonic assisted direct melt reaction. Results indicate ultrasonic chemistry reactions are both accelerated and more complete compared to traditional in situ reactions. Al3Ti reinforced particles with a regular shape and size of 1-2 μm were well distributed and as-cast microstructures of composites were superior. Composite particles under ultrasonic assistance were also refined to a greater extent. Tensile strength and elongation rate of the composites reached 255 MPa and 2.2%, an increase of 19.1% and 37.5% respectively to those without ultrasonic aid. Cleavage surface of the composite declined and the number of dimples increased while dimples became smaller and deeper, showing obvious ductile fracture.

Cemented sand gravel (CSG) is different from ordinary concrete in its mechanical properties such as elastic modulus due to the non-sieving of aggregate. On the basis of previous studies, the serial model, parallel model, Hashin-Shtrikman model and the elastic modulus prediction method based on the mesoscopic random aggregate simulation have been analyzed, and the influences of different mesoscopic component parameters on the elastic modulus calculation of the above four methods have been studied. The results show that the elastic modulus and tensile strength of meso component have great influence on the elastic modulus of random aggregate simulation, the elastic modulus of cement mortar has the largest impact on the series model and the Hashin-Shtrikman lower boundary model, and the elastic modulus of the aggregate has the greatest influence on the parallel model and the Hashin-Shtrikman upper boundary model. This paper proposed to determine the meso-component parameters of the elastic modulus prediction model through mesoscopic inversion, studied the correlation between the meso-component volume fraction and the overall elastic modulus of the material, and by adding a correction factor to the correlation, concluded that when the meso-component volume fraction falls between 35% and 55%, the random aggregate model-based prediction and the equivalent theoretical model can better predict the elastic modulus of the CSG. This study may provide theoretical basis for CSG mix design and multi-scale model research.

In order to develop 960MPa grade high strength steel, the effects of cooling rate and austenite deformation on the hardness and the microstructure of high strength steel has been studied by Scanning Electron microscope (SEM), Transmission Electron Microscope (TEM), Gleeble-3500 thermal simulation testing machine and T2500 Vickers hardness tester. The results show that only when the cooling rate was higher than 10∘C/s and the final cooling temperature was lower than 250∘C, the microstructure mainly consists of martensite, and the strength of high strength steel could be above 960MPa; and austenite deformation could effectively refine the width of martensite lath, thus improving the strength and toughness.

Infiltrated molten Al matrix by mechanical-pressure infiltration method into the ceramic scaffold prepared by freeze-drying technology could prepare dense lamellar Al matrix composites without damage of the biomimetic microstructure of the scaffold. However, the investigation of lamellar Al matrix composites prepared by freeze-drying and mechanical-pressure infiltration method has not been fully understood yet. In the present work, the Al2O3 scaffold with pearl layer structure was prepared by freezing-dry method, and eventually the lamellar Al2O3p/Al composite was fabricated by mechanical-pressure infiltration method. The Al matrix was infiltrated well into the large pores of the Al2O3 scaffold, and the lamellar structure of the Al2O3 was well preserved. The hardness of the lamellar Al2O3p/Al composite was isotropic in transvers and perpendicular directions. However, the compressive strengths of the lamellar Al2O3p/Al composite were significant anisotropic while the compressive strength in transvers direction was 127.7% higher than that in the perpendicular direction, indicating the integrality of the lamellae microstructure (especially the bridging layers). Due to the mismatched deformability, weak debonding was observed between Al and Al2O3p/Al layers in the fracture surface of the lamellar Al2O3p/Al composite. It indicates that the interfacial bonding between Al and Al2O3p/Al layers is rather strong, which is beneficial for higher strength in transvers direction but lead to lower strength in perpendicular direction.

In this work, geopolymer foam composites containing waste basalt fibre (10, 30, and 50%wt) were exposed to elevated temperatures of 200, 400, 600, 800 and 1000∘C. With an increase in high temperature, the geopolymer foams material exhibits a decrease in compressive strength and bending strength. When heated above 600∘C, geopolymer foams materials exhibit a significant reduction in mechanical properties. It shows clearly with the naked eye that surface cracks in case of samples containing 10% of basalt filler. However, when increasing fillers with basalt fibres up to 30% and 50%, the cracking of the sample surface is no longer visible to the naked eye. Especially when the temperature increases, the mechanical properties also increase without decreasing in the sample of 50% by weighing to the binder. The results show that reinforcing the geopolymer foams with basalt ground fibre improves the mechanical properties at high temperatures.

In this work, we modified nylon 6 with liquid rubber by in-situ polymerization. The infrared analysis suggested that HDI urea diketone is successfully blocked by caprolactam after grafting on hydroxyl of HTPB, and the rubber-modified nylon copolymer is generated by the anionic polymerization. The impact section analysis indicated the rubber-modified nylon 6 resin exhibited an alpha crystal form.With an increase in the rubber content, nylon 6 was more likely to generate stable α crystal. Avrami equation was a good description of the non-isothermal crystallization kinetics of nylon-6 and rubber-modified nylon-6 resin. Moreover, it is found that the initial crystallization temperature of nylon-6 chain segment decreased due to the flexible rubber chain segment. n value of rubber-modified nylon-6 indicated that its growth was the coexistence of two-dimensional discoid and three-dimensional spherulite growth. Finally, the addition of the rubber accelerated the crystallization rate of nylon 6.

The normal stress along the shear plane has great effect on the composite intralaminar shear strength. However, the influence mechanism on composite interlaminar shear strength under the normal stress along the shear plane was not truly reflected by the double-notch shear experiment. In this paper, the interlaminar shear strength of composite specimens under different external normal stresses was first obtained using the improved double-notch shear experiment. Furthermore, to research the influence mechanism on interlaminar shear strength under normal stress along the shear plane, the characteristic curve method based on the double-notch shear specimen was studied. Finally, the experimental results analyzed by the characteristic curve method were compared with a range of failure criteria presented in the literature. The experimental data obtained in this study agreed best with the NU theory criterion, with a maximum numerical difference of 4%. And the NU theory criterion can reflect the influence mechanism of the composite interlaminar shear strength best.

In this paper, C200 ultra-high performance concrete (UHPC) containing coarse aggregate was prepared. Firstly, four different maximum size and three different type of coarse aggregate having significant differences in strength, surface texture, porosity and absorption were used to prepared the mixtures. Secondly, the effect of maximum size and type of coarse aggregate on the workability of the fresh UHPC and the mechanical behaviour of harden UHPC were investigated. Finally, a series micro-tests including mercury intrusion porosimetry (MIP), scanning electron microscope (SEM), X-ray diffraction (XRD) were conducted and the mechanism of the C200 UHPC were discussed. The results show that the type and maximum size of coarse aggregate have significant effect on the workability and mechanical properties of C200 UHPC. The basalt coarse aggregate with maximum size of 10mm can be used to prepare the C200 UHPC. The compressive strength and flexural strength of the C200 UHPC is 203MPa and 46MPa at 90 day, respectively. Besides, the micro-tests data show that the C200 UHPC has a compacted matrix and strong interface transition zone (ITZ), which make the aggregate potential strength fully used.

A data set of cemented sand and gravel (CSG) mix proportion and 28-day compressive strength was established, with outliers determined and removed based on the Boxplot. Then, the distribution law of compressive strength of CSG was analyzed using the skewness kurtosis and single-sample Kolmogorov-Smirnov tests. And with the help of Python software, a model based on Back Propagation neural network was built to predict the compressive strength of CSG according to its mix proportion. The results showed that the compressive strength follows the normal distribution law, the expected value and variance were 5.471 MPa and 3.962 MPa respectively, and the average relative error was 7.16%, indicating the predictability of compressive strength of CSG and its correlation with the mix proportion.

In view of the limitation of wide application of polypropylene(PP) with low strength, poor low-temperature brittleness and easy combustion, a kind of PP matrix nanocomposites was designed and prepared. Sb2O3 nanoparticles (nano-Sb2O3) modified by silane coupling agent of KH550 were dispersed into brominated polystyrene(BPS)-PP matrix by ball milling dispersion and melt blending method, respectively. And the nano-Sb2O3/BPS-PP composites samples were obtained by injection molding method. The effects of nano-Sb2O3 particles on mechanical properties of nano-Sb2O3/BPS-PP composites were investigated. The results showed that the surface of nano-Sb2O3 particles was successfully modified by the KH550 and the interfacial adhesion between nano-Sb2O3 and PP matrix was improved. With increasing of the mass fraction of nano-Sb2O3, the tensile strength and impact strength of nano-Sb2O3/BPS-PP composites were improved accompanying by increasing of crystallinity and refining grain of the composites. When the mass fraction of nano-Sb2O3 was 3 wt%, the tensile strength of nano-Sb2O3/BPS-PP composites was 43 MPa, which was 30.3% higher than that of PP. When the mass fraction of nano-Sb2O3 was 2 wt%, the impact strength of the composites was 44.19 kJ·m−2, which was 30.8% higher than that of PP.