Band 27, Heft 1

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 Al 2 O 3 scaffold with pearl layer structure was prepared by freezing-dry method, and eventually the lamellar Al 2 O 3 p/Al composite was fabricated by mechanical-pressure infiltration method. The Al matrix was infiltrated well into the large pores of the Al 2 O 3 scaffold, and the lamellar structure of the Al 2 O 3 was well preserved. The hardness of the lamellar Al 2 O 3 p/Al composite was isotropic in transvers and perpendicular directions. However, the compressive strengths of the lamellar Al 2 O 3 p/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 Al 2 O 3 p/Al layers in the fracture surface of the lamellar Al 2 O 3 p/Al composite. It indicates that the interfacial bonding between Al and Al 2 O 3 p/Al layers is rather strong, which is beneficial for higher strength in transvers direction but lead to lower strength in perpendicular direction.

Al 3 Ti/ADC12 composite was synthesized in situ using Al-fluoride potassium titanate (K 2 TiF 6 ) 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. Al 3 Ti 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.

A V-doped titania catalyst was synthesized on titanium substrate by micro-arc oxidation and then it was carried out by heat treatment in nitrogen atmosphere. The surface characteristics of the synthesized titania coatings were investigated by SEM, EDS, XPS and XRD. The synthesized TiO 2 coating doped with V (in form of V 2 O 3 and V 2 O 5 ) showed a large amount of “cellular” bulges with more microscopic defects. The anatase phase of the TiO 2 coatings after heat treatment tended to be transformed into rutile phase. As a result, the corrosion resistance and photocatalytic performance of TiO 2 coating doped with V after heat treatment had been enhanced.

The effect of CNTs on the mechanical and damping properties of macro-defect-free (MDF) cements was studied, and polyvinyl alcohol (PVA) fibers were also studied as a contrast. It was found that the compressive strength of MDF cements was not significantly affected by the two types of fibers. The CNTs enhanced the flexural strength of MDF, while PVA fibers made negative contribution. The strengthening mechanism of flexural strength of MDF cements by CNTs can be summarized as fiber bridging, crack deflection and fiber slippage. For the damping properties, the proper contents of CNTs and PVA fibers improved the loss factor significantly. The interface transition zone (ITZ) between the PVA fibers and matrix was large, which was favorable for fiber slippage. The damping property of MDF cements with CNTs was mainly due to the slippage between the inner tubes of the CNTs rather than the slippage between the CNTs and matrix.

With the continuous advancement of space exploration missions, the mechanical environment for planetary detectors is becoming increasingly severe. As a result, fatigue, fracture, large deformation and other forms of failures are more likely to occur at the load-bearing structures. As a critical part of the load-bearing structure of a goat, goat tibia has remarkable toughness because of its unique microstructures. In this investigation, firstly, the cortical bone of goat tibia was observed by SEM, and the characteristic microstructures in different regions were identified. Secondly, the cross section of cortical bone was loaded by long-term inplane stress, then the toughness of cortical bone in different regions are obtained and compared based on the orientation and distribution of cracks after the load. Thirdly, a simplified FEM model mimicking typical microstructure of the cortical bone is proposed using cohesive modeling, and then the toughening mechanism of the typical microstructure is validated with numerical simulation. Finally, the toughening mechanisms of cortical bone were discussed according to the SEM observation as well as the numerical simulation. This study of the toughening mechanism of cortical bone can be helpful for the biomimetic design of high-toughness structures.

Polyvinyl Vinyl Chloride (PVC) multiwall carbon nanotubes (MWCNTs) nanocomposite flexible films were prepared using the solvent blend technique. Chloroform (CHCl 3 ) and tetrahydrofuran ((CH 2 ) 4 O) were used as solvents for MWCNTs and PVC, respectively. The effect of the solvents’ blend on electrical, optical and thermal properties of PVC/MWCNTs were investigated. The results of the Raman spectrum showed that all the characteristic bands of PVC polymer have a slight shift due to addition of MWCNTs. Electrical results showed that the nanocomposite samples with chloroform volume ratios of 10% and 25% had nearly the same conductivity. This is attributed to the formation of the MWCNTs network, which assisted in electrical conductivity. The I-V hysteresis curve decreases as the temperature increases and as it approaches the glass transition temperature. The non-isothermal kinetics analysis for PVC and PVC/MWCNTs were investigated by Thermogravimetry Analysis (TGA) using the model-free kinetic method. The non-isothermal measurements were carried out at five heating rates of 5 to 40 ∘ C/min. The results show that the main decomposition process has constant apparent activation energies for all samples. The use of the bi-solvent method has improved the dispersion of untreated MWCNTs, and this has been reflected on the stability of both electrical and thermal properties.

Cement Sand and Gravel (CSG) is a low-cost, environment-friendly composite material mixed of unscreened aggregate, cement, fly ash and water, and its properties differ from ordinary concrete due to different aggregate characteristics. In order to investigate the effect of aggregate characteristics on the mechanical behavior of CSG, this paper used numerical simulation method to divide the CSG into aggregate unit, cement mortar unit and interface unit at the mesoscopic level and randomly generate aggregate, then used laboratory uniaxial compression test results to inverse the said mesoscopic component parameters, and finally verified the rationality of mesoscopic numerical simulation. Based on the inversed parameters, the numerical simulation test of different aggregate grading was carried out and analyzed. The results showed that: (1) From the perspective of macroscopic mechanical properties, as the sand ratio increased, the aggregate occupancy and the peak stress decreased; under the same aggregate occupancy (the same sand ratio), the stress peak became higher with the improvement of aggregate grading (aggregates of small particle size increased); (2) At the mesoscopic level, the crack of CSG usually appeared on the interface and around the aggregate; the smaller the sand ratio was, the higher the aggregate occupancy was, the more obvious the stress concentration was, and the earlier the cracking of the test piece was, but there were many aggregates, so the eventual failure time was delayed. These research results can provide theoretical basis for engineering design and construction.

The concrete-filled steel tubular (CFST) arch is a new high-strength support form for a mine roadway in deep/soft rock stratum; however, the bearing characteristics have not been clearly elucidated for scientifically guiding field applications. Numerical simulation tests with 15 schemes shaped as a ‘half circle with two straight legs’ and 10 schemes shaped as a circle were conducted, and the main responses of the numerical model were verified by performing the laboratory tests to evaluate the basic CFST structures and global CFST arches. The bearing and failure behaviors of the CFST arches were studied, and the influence laws, in terms of the arch shape, size and lateral pressure coefficient λ , were further investigated. The results show that the bearing capacity of a circular arch is significantly higher than that of a straight-leg arch under a uniform load. Furthermore, the bearing capacity of the circular arch decreases considerably with the increase in the arch size or λ . In addition, the bearing capacity of a straight-leg arch decreases with the increase in the leg height and arch size; however, it first increases and later decreases with the increase in λ . The failure modes of all the arches correspond to the instability at the extreme point caused by the strength deterioration, except in the case of a circular arch under a uniform pressure, the failure mode of which corresponds to the instability at the branch points. Finally, the recommendations for the field practice are proposed and verified.

To achieve cost-efficient manufacturing and a high part quality in Thermoset Automated Fiber Placement (TS-AFP), knowledge about the interaction between material and process parameters is of special interest. Material properties of prepregs are well known at the cured state of the resin. However, there are no standardized test procedures for the mechanical behavior of the uncured prepreg tapes. To investigate the intra-ply shear deformation behavior of uncured unidirectional prepreg tapes, we compared several measurement procedures and conducted experiments for rheometer based tests using 8552/AS4 material. We identified a rotational parallel platens rheometer test method and a torsion bar rheometer test method to be suitable. Experiments using both methods revealed that the Torsion Bar Test has a higher repeatability and the analysis is less complex. Furthermore, first results show that changes in material properties caused by aging can be analyzed using this method. In the future,we will use the Torsion Bar Test to characterize changes in deformation behavior due to material aging as well as material modifications. By this, we will be able to provide data for the material modeling thus enabling the prediction of lay-up defects such as buckling due to steering.

Aluminum alloys with ceramic reinforced particulates are made prospective in aerospace, transportation, and industrial applications ampler to their low mass density, stiffness, and high specific strength. In this work, Aluminium Alloy(AA) 7010 - TiB 2 (Titanium Diboride) composites with different amounts of reinforcement (5, 7.5 and 10 wt.%) were produced by the exothermic reaction of halide salts K 2 TiF 6 and KBF 4 added in 120% excess to the stoichiometric ratio with molten AA7010.The effect and dispersion of TiB 2 particulates in AA7010 were analyzed by microstructural, mechanical and corrosion behavior. The dispersion of reinforcement in the matrix alloy was analyzed by optical microscope and field emission scanning electron microscope (FESEM) images. X-ray diffraction patterns of the prepared composites reveal the formation of TiB 2 particles in the matrix alloy. Indeed samples are tested according to ASTM G34 standard for ex- foliation corrosion rate by weight loss method. The result shows improved hardness, tensile strength and yield strength of composites to about 35%, 260%, and 240% respectively. The mechanical and corrosion resistance of 10% TiB 2 shows better results compared with matrix alloy and other concentrations of reinforcements.

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.

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 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 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. Sb 2 O 3 nanoparticles (nano-Sb 2 O 3 ) 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-Sb 2 O 3 /BPS-PP composites samples were obtained by injection molding method. The effects of nano-Sb 2 O 3 particles on mechanical properties of nano-Sb 2 O 3 /BPS-PP composites were investigated. The results showed that the surface of nano-Sb 2 O 3 particles was successfully modified by the KH550 and the interfacial adhesion between nano-Sb 2 O 3 and PP matrix was improved. With increasing of the mass fraction of nano-Sb 2 O 3 , the tensile strength and impact strength of nano-Sb 2 O 3 /BPS-PP composites were improved accompanying by increasing of crystallinity and refining grain of the composites. When the mass fraction of nano-Sb 2 O 3 was 3 wt%, the tensile strength of nano-Sb 2 O 3 /BPS-PP composites was 43 MPa, which was 30.3% higher than that of PP. When the mass fraction of nano-Sb 2 O 3 was 2 wt%, the impact strength of the composites was 44.19 kJ·m −2 , which was 30.8% higher than that of PP.

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.

In the present study, the effect of construction waste and pulverized lime on the strength of Shanghai clayey soil is investigated. The unconfined compressive strength and direct shear tests have been carried out on reinforced soils with different combinations of construction waste and pulverized lime over various curing periods. The results from unconfined compressive tests show that the compressive strength increases after introduction of construction waste and pulverized lime, and the longer the curing period the higher the strength of treated soil. The results from direct shear tests show that the shear strength parameters increase to different degree after mixing with construction waste and pulverized lime. The tests also show the increase in compressive strength is insignificant with the addition of construction waste alone, but ductility increases. The conclusions drawn from the present study are important not only for designing and construction of geotechnical engineering projects in practice, but also for making good use of waste material, sustainable development and environmental protection.

In this study, the microstructure and wear behaviours of aluminium composites, reinforced with different amounts of (3-12%) Al 2 O 3 and 2% (% vol.) graphite were investigated. The Al 2 O 3 and graphite were added to Al matrix and mechanically alloyed for 60 minutes. Subsequently, the mechanically alloyed powders were pressed under 700MPa pressure and sintered at 600 ∘ C for 120 minutes. The produced aluminium composites were characterized by microstructure, scanning electron microscope (SEM), X-ray diffraction (XRD), density and hardness measurements. Afterwards, wear tests were carried out on a block on-ring type wear testing device, under three different loads and four different sliding distances. As a result, the hardness and density of composites were observed to increase due to the increase in the amount of reinforcement in aluminium composites. The highest hardness and density values were obtained in composite material containing 12% Al 2 O 3 . The wear tests, the lowest weight loss was also obtained in composite containing 12% Al 2 O 3 .

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.

In this study, a thermal buckling analysis of laminate composite square plate was performed with elliptical hole cutout using the finite element method. Graphite/Epoxy laminate plate used in this study is symmetrical stacking sequence plate [(0/90) 2 ] s . This laminate square plate was subjected to temperature loading with clamped support on all edges. Moreover, the parameters considered were fiber orientation ( θ ), a/b ratio (elliptical hole), elliptical hole inclination ( φ ), thermal expansion coefficient ratio ( α 1 / α 2 ), and thickness of plates (t). The results showed that as the thermal expansion coefficient ratio changes, the elliptical hole ratio and the elliptical hole inclination have inconsequential effects on the performance of the resistance of laminate composite plates. The maximum values of thermal buckling amplification factor were obtained when the ratio a/b = 1.0, which is a circle cutout,while the minimum values were obtained when the ratio a/b = 0.5, regardless of the thickness of plates. Moreover, the plate with elliptical or circle cutout hole provides about 4% to 9% higher buckling resistance than that of the plate without hole cutout, because when subjected to temperature loading the plate with hole can release stress better than the plate without hole.

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.

Recently, basalt fiber reinforced polymer (BFRP) is acknowledged as an outstanding material for the strengthening of existing concrete structure, especially it was being used in marine vehicles, aerospace, automotive and nuclear engineering. Most of the structures were subjected to severe dynamic loading during their service life that may induce vibration of the structures. However, free vibration studied on the basalt laminates composite plates with elliptical cut-out and correlation of natural frequency with buckling load has been very limited. Therefore, effects of the elliptical hole on the natural frequency of basalt/epoxy composite plates was performed in this study. Effects of stacking sequence ( θ ), elliptical hole inclination ( ϕ ), hole geometric ratio (a/b) and position of the elliptical hole were considered. The numerical modeling of free vibration analysis was based on the mechanical properties of BFRP obtained from the experiment. The natural frequencies as well as mode shapes of basalt laminates composite plates were numerically determined using the commercial program software (ABAQUS). Then, the determination of correlation of natural frequencies with buckling load was carried out. Results showed that elliptical hole inclination and fiber orientation angle induced the inverse proportion between natural frequency and buckling load.

In this study, the effective elastic modulus ( E c ) of a cellulose nanocrystal fiber reinforced polymer composite was evaluated using the Mori-Tanaka and finite element (FE) model. The FE model was generated using a representative volume element with a periodic boundary condition. The mass fractions of the fiber in the composites ( MF f ) were set to 1, 2, and 3 wt.%. Elastic modulus values for interphase were input and were either uniform or exhibited a gradient. The E c for the uniform interphase region increased significantly with MF f , but was relatively low for interphase regions exhibiting a gradient. The results show that interphase parameters must be considered carefully when predicting E c using the FE model.

This work focuses on dip coating and further phase inversion prepared polysulfone/LTA zeolite mixed matrix membranes ( MMMs ). The Linde Type A (LTA) zeolite synthesized under hydrothermal conditions by the organic free method was introduced as fillers at 10 and 20 wt.% loadings into the polysulfone polymer matrix to obtain MMMs . The x-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the as-synthesized LTA zeolite samples were crystalline and mainly composed of crystal of predominantly cubic shape. Textural characterisation using Ar adsorption/desorption data of LTA zeolite shown the existence of mesoporous. Atomic force microscopy (AFM) in combination with the SEM characterised the membrane morphology and the dispersion of zeolite fillers. The effect of the zeolite loading on the performance of the MMMs was analysed. It points out that N2 permeability was increased with the increment of zeolite filler, also the high membranes permeability and the weak dependence upon transmembrane pressure and therefore its high selectivity. The average membrane thickness was 150 μm.

In this study, the foam sandwich panels were manufactured by integrating top facesheet and bottom facesheet with pyramidal lattice stitched core to overcome the weak interface between the core and skins of the sandwich structures. Low-velocity impact test and numerical simulation were conducted to reveal the failure mechanisms and energy absorption capacity at sandwich composite with foam core, different strut stitched foam core under different impact energy. The experimental results show showed that the strut core can improve the impact resistance of the specimen, and which is closely related to the diameter of the strut core. Compared with foam sandwich structure, pyramidal lattice stitched foam sandwich composites have comparable specific energy absorptions. The failure modes were also analyzed which is: fiber breakage, delamination, foam deformation and strut core breakage. The research presented here confirms that numerical simulation show good agreement with the experiment.

Because of its light weight, high strength, designable, composite materials are more and more widely used in the field of aerospace, especially in the field of general aviation. In this paper, the structural design and analysis of the composite wing (include wing beam, rib, skin, leading edge and trailing edge) of a four-seater electric aircraft were carried out. The finite element numerical analysis model of the composite wing was established, and the deformation and strain distribution of the composite wing under the limited load required by airworthiness regulations were calculated. Finally, the static test of the whole composite wing was carried out to verify the accuracy of the finite element results. The finite element analysis and testing results showed that the structural design of the composite wing of the electric aircraft meets the structural strength requirements specified in the airworthiness standard (part 23 of China civil aviation regulations: air-worthiness requirements for normal, practical, special effects and commuting aircraft: CCAR 23-R3)

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.

The spin forming parameters of bimetallic composite pipe were optimized by FEM and experiment, and the torque and the residual contact pressure were analyzed during forming process. Adoption of The orthogonal test of four factors and five levels to gain the optimal spinning parameters ( δ = 0.16mm, Ψ = 0.4mm, β = 3.0 ∘ , f = 0.5) and the effects of factors on analysis indicators under the condition of maximum residual contact pressure and small torque. The simulation results showed that the residual contact pressure was nearly 1MPa higher and the torque was lower about 160N·m than unoptimized results. It proved that the orthogonal test method was effective for the optimization of spinning parameters of bimetal composite tube. The accuracy of numerical simulation value was verified by the drawing experiment of the composite tube.

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.

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.

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 ε c 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.

Carbon Fiber Reinforced Polymer (CFRP) composite materials have been widely used in high-tech fields because of their outstanding physical properties. However, barely visible impact damage can be introduced by low velocity impact, which might bring tremendous risk. Monitoring impact forces is essential for the integrity and reliability of CFRP structures. In this paper, a reverse localization scheme on CFRP composite materials is developed. The scheme is based on a predictive mode of attenuated strain wave. The signals induced by low velocity impact are obtained by strain gauges. The proposed localization scheme has been verified by experimental tests of the CFRP plates with symmetrical stacking [0/45/90/−45] 2 s The errors occurring in the test can be accepted for engineering application. The calculated impact locations are generally in consistent with the testing impact locations.

The type of floor in a building object results from the serviceability requirements, technical possibilities, and costs of its implementation. Concrete screeds constituting the structural layer of the floor can be made without reinforcement, with dispersed reinforcement, or reinforced with meshes of various materials. Due to the large surface dimensions, concrete screeds are susceptible to scratches as a result of occurring strains, service loads and unevenness of the floor. There are detailed recommendations on how to make floors, and on the materials used. However, the conditions in which floors are made often differ from those recommended. The article presents the results of measured strains on the surfaces of three screeds constituting the floor layer in a residential building. The screeds, which were made in identical environmental conditions, differed in the type of reinforcement used: steel mesh, dispersed polypropylene fibres, fibreglass mesh. In addition, strain measurements were carried out on concrete and fibre-reinforced concrete specimens made of the mix used to make the screeds. The results allowed the assessment of the effectiveness of the reinforcement used, the impact of environmental conditions on the values, and the analysis of differences in the course of strains in real elements and the specimens.

In this paper, a multi-zone self-heating composite tool is developed to manufacture out-of-autoclave complex and high-quality business jet lower wing stiffened composite panel. Autoclave manufacturing is regarded as a benchmark for manufacturing aerospace-grade composite parts. However, high accruing operational costs limit production rates thereby not being practical for smaller-scale companies. Therefore, significant work towards developing out-of-autoclave manufacturing is underway. In this study, a production line tool is developed with embedded heating fabric that controls temperature at the desired zones, replacing the need for autoclave cure. It investigates and identifies the optimal design parameters of the self-heating setup namely the placement of the heating fabric, zones, thermal management system, temperature distribution, heating rate and thermal performance using a thermal FEA model. The associated thermal characterisation of the tooling material and the part are measured for accurate simulation results. The design developed in this study will be used as production guideline for the actual tool.

To investigate the effect of notches on static and fatigue properties of T800 fabric carbon fibre reinforced epoxy, comparative tests were conducted between specimens of three depths of notches and un-notched specimens. Results demonstrate that the residual tensile strength of specimens is linearly decreased with the increasing depth of notches from 2mm to 4mm. The tensile strength on notched specimens dropped 31.5% comparing with no-damaged laminate. Due to the effect of notches, the fatigue limit was reduced to 55% of UTS and the slope of the S - N curve tends to be horizontal. In-situ damage expansion process was observed and the shape of proposed normalized S - N curves could be explained and concluded as two stages: the first stage accounts for 20% of the fatigue life, showing a dramatic decrease of fatigue strength; the remaining stage takes up the rest of the total life span, representing a steady decline in strength. It shows that no-damaged and notched laminates exhibit different behaviours in terms of damage evolution.

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.

The Pb(Ni 1/3 Nb 2/3 )O 3 -Pb(Zr x Ti 1− x )O 3 (PNN-PZT) piezoelectric ceramics with CuO and LiBiO 2 doping were successfully fabricated by the low-temperature solid-state reaction to effectively restrain the PbO volatilization. The microstructure and electrical properties of the PNN-PZT ceramics were characterized. The experimental results reveal that the PNN-PZT ceramics are composed of a pure perovskite structure in which the rhombohedral and tetragonal phases coexist. Meanwhile, the good electric properties, including low dielectric loss, outstanding diffusion phase transition and palpable dielectric relaxation, are exhibited in PNN-PZT ceramics with 0.2 wt.% CuO and 1 wt.% LiBiO 2 addition. This piezoceramic composition possibly provides a reference for the application of multi-layer piezoelectric actuators.

The rheology of cement paste under vibration follows the transformation from Bingham model to Hershel-Bulkly model to Power-Law model. Most of the existing research is obtained through a large number of experiments in the data fitting process, and cannot express the time-varying characteristics of viscosity. Furthermore, thixotropy of cement paste is based on static experiment and cannot be applied under vibration. In this paper a shear-vibration equivalent theory is proposed, which consider the effect of vibration is the same as the shear effect on the viscosity change of cement paste. Combining vibrational shear equivalent theory and HI theory, the rheological changes of cement paste under vibration are obtained through numerical simulation. This theory has been verified by a series of experiments with numerical simulations, and can be used to study the rheology of concrete under vibration.

Brakes are one of the most important components of vehicle. The brake system must be reliable and display unchanging action throughout its use, as it guards the health and life of many people. Properly matched friction pair, a disc and brake pad (in disc brakes), have a great impact on these factors. In most cases, the disc is made of grey cast iron. The brake pads are far more complex components. New technologies make it possible to develop materials with various compositions and different proportions, and connect them permanently in fully controllable processes. This elaboration shows that all these factors have a greater or lesser impact on the coefficient of friction, resistance to friction wear and high temperature, and brake pad’s operating life. This review collects the most important, the most interesting, and the most unconventional materials used in production of brake pads, and characterizes their impact on the tribological properties of pads.

The meso numerical simulation has become an important method to study the characteristics of materials; however, the key to its further application is determining the parameters of meso-constitutive model. Considering that the meso-scale parameters of materials are hard to measure, this paper took into account the aggregate size effect and proposed a meso-parameter identification method by combining random aggregate numerical simulation and genetic algorithm. First, a random aggregate model of concrete was established, and its meso-model parameters were analyzed. The Morris method was used to analyze the sensitivity of meso-component parameters to the macro-responses, and results showed that the elastic modulus of mortar matrix, interface and large aggregates had a great effect on the peak strain and that the elastic modulus, Poisson’s ratio and tensile strength of interface and mortar matrix, as well as the Poisson’s ratio of large aggregates and the elastic modulus of small aggregates all had an effect on the peak stress, among which the interface tensile strength produced the greatest effect. Second, a parametric inversion and optimization function was established. The uniaxial compression numerical simulation test and genetic algorithm were combined to invert the meso-parameters, and results showed that compared with the single-aggregate parameter inversion curve, the multi-aggregate inversion stress-strain curve was much closer to the measured curve. That was because the aggregates of small size had lower elastic modulus, easing the stress concentration at the interface between aggregates and cement stone, and delaying the formation and growth of cracks.

The article describes a method of creating a mesoscale finite element model of a fabric reinforced laminate that replicates the smallest repetitive fragment of its microstructure – RUC (Repetitive Unit Cell). The model takes into account the influence of the number and orientation of layers, the weave of the reinforcement fabric as well as manufacturing technology on the strength and stiffness of the laminate. The constants of the finite elements forming RUC (equivalent cross-sectional parameters, limit values of forces ensuring layer integrity) are determined experimentally by performing uncomplicated tests of specimens of a particular laminate. A special preprocessor was developed to generate the finite element model of the construction element from laminate, which automatically creates the so-called batch file defining the model. The usefulness of the preprocessor was checked by simulating a three-point bending test of a laminate door beam of a passenger car. The obtained calculation results were verified experimentally.

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.

In the present contribution, an environmental-friendly and cost-effective adsorbent was reported for soil treatment and desertification control. A novel foam gel material was synthesized here by the physical foaming in the absence of catalyst. By adopting modified microcrystalline cellulose and chitosan as raw materials and sodium dodecyl sulfonate (SDS) as foaming agent, a microcrystalline cellulose/chitosan blend foam gel was synthesized. It is expected to replace polymers derived from petroleum for agricultural applications. In addition, a systematical study was conducted on the adsorbability, water holding capacity and re-expansion performance of foam gel in deionized water and brine under different SDS concentrations (2%–5%) as well as adsorption time. To be specific, the adsorption capacity of foam gel was up to 105g/g in distilled water and 54g/g in brine, indicating a high water absorption performance. As revealed from the results of Fourier transform infrared spectroscopy (FTIR) analysis, both the amino group of chitosan and the aldehyde group modified by cellulose were involved. According to the results of Scanning electron microscope (SEM) analysis, the foam gel was found to exhibit an interconnected pore network with uniform pore space. As suggested by Bet analysis, the macroporous structure was formed in the sample, and the pore size ranged from 0 to 170nm. The mentioned findings demonstrated that the foam gel material of this study refers to a potential environmental absorbent to improve soil and desert environments. It can act as a powerful alternative to conventional petroleum derived polymers.

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 aim of the present work is to upgrade the functionality and environmental friendliness of polypropylene (PP) by means of a blending technique. The influence of the metal pigment on the odor, volatile organic compounds (VOC) and metal texture of PP, and the effects of the extractant, adsorbent and processing technology on the odor and VOC of PP composites were studied systematically. It was found that metallic pigment significantly increased the VOC, odor, metallic texture and MFR of PP, and reduced the impact strength and elongation at break. The adsorbent and extractant can effectively reduce the VOC and odor of the PP composites. When the adsorbent and extractant contents were 0.5 and 5 wt%, respectively, the maximum reduction in the VOC and odor reached 73.6% and 1 level, respectively. When the extractant and adsorbent were used at the same time, the method of adding extractant and adsorbent from the main and the secondary feeding port respectively was significantly superior to the method of adding the extractant and adsorbent from the main feeding port together in reducing the odor and VOC of PP composites, which displayed a good synergistic effect.

The internal curing technology has been widely applied to high-strength concrete, for it can make the high-strength concrete marked by low shrinkage and durable frost resistance. The key to its extension and application lies in the reasonable mixing amount of internal curing materials. To address this problem, scholars have proposed a method for determining the water demand in internal curing; however, the water release of internal curing materials is difficult to obtain by measurement due to the mixing method. Therefore, this paper proposed a calculation model for the mixing amount of internal curing materials based on the modified MULTIMOORA method (Multi-Objective Optimization on the basis of Ratio Analysis plus full multiplicative form). First, different internal curing materials (super absorbent polymer (SAP), lightweight aggregate (LWA)) and pretreatment methods were selected to calculate their compressive strength, self-shrinkage and frost durability according to a proposed test scheme on the mixing amount of internal curing materials, and in such case, the comprehensive performance evaluation of the above indexes was turned into a multi-attribute decision-making problem. Second, the ordered weighted averaging (OWA) method and the entropy weight method were used to determine the subjective and objective weights of the indexes respectively, to eliminate the impact of outliers in the subjective evaluation values. Finally, the comprehensive performance of each test group was sorted using MULTIMOORA, and based on the sorting results and the calculation model, the mixing amount of internal curing materials was determined. The numerical example application results showed that the mixing amount of SAP curing material calculated based on the model herein was 1.276 kg/m 3 , and the mixing method adopted the pre-water absorption method with the total water-binder ratio unchanged. The numerical example evaluation results were in good agreement with the test results. The internal curing effect of SAP was better than that of LWA, and reached the best when the mixing amount was calculated at 25 times the water release rate and the requirement for the maximum total water diversion was met. The study may provide new ideas for extension and application of the internal curing technology.

In order to accurately evaluate the service life and failure mechanism of the PZT piezoelectric ceramics, the electric degradation process of the PZT ceramics with and sans doping under a DC voltage of 380V, in a surrounding environment of 90 ∘ C and 85% RH has been investigated using a self-made device. The experimental results show that the degradation rate of the pure PZT ceramic is lower than that of ceramics with doping in the same condition. Furthermore, the electrical properties of the ceramics tend to decrease during the electric degradation. The doping increases the defects of ceramics, resulting in that the silver ion transfer from the anode to the cathode under the continuous DC bias, which can further form a metal band, increasing the conductivity, but deteriorating the service life.

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.