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To study the influence of different mixing times on the performance of concrete under vibration mixing and conventional mixing, C40 and C60 are selected in this paper to verify the influence of mixing time of 60, 75, 90, 105, and 120 s on the compressive strength and durability of concrete comparing vibration mixing and common forced mixing. The results show that the early strength of concrete is more significantly improved in 3 and 7 day; the strength with vibration mixing for mixing 105 s in each age is higher than that of conventional mixing at 120 s; under the condition of guaranteed strength, the mixing time of at least 15 s can be reduced. The strength of C40 concrete with vibration mixing has a peak value with the corresponding mixing time of 105 s, and the rapid growth stage of compressive strength is 15 s earlier than that of conventional mixing. For all mixing time, the electric flux of vibrated concrete is significantly smaller than that of forced concrete, and the change rate is generally above 10%; compared with conventional mixing for 120 s, the durability of C40 and C60 concrete increases by 11.8 and 11.1%, respectively, at the time of vibration mixing for 105 s. It was found that under the same mixing time, the compressive strength of concrete with vibration mixing method is higher than that of conventional mixing. In a certain range, the durability of concrete can be improved by prolonging the mixing time.

Superelastic shape memory alloy (SMA) as an advanced smart material has been used to improve the impact performance of fiber-reinforced composites in recent decades. Due to the low impact toughness of the thin composite face-sheet and the poor strength of the foam core, sandwich panels are sensitive to the transverse loading. SMA fibers were embedded into the composite laminated to improve the impact resistance of the traditional foam core sandwich panel in this work. Five new types of SMA hybrid panels were prepared, and the testing panels with penetration failure were observed at the impact energy of 50 J. The impact mechanical responses and the damage morphology were analyzed, and the impact failure mechanism was also revealed. Results show that all sandwich panels were failed, the fiber breakage occurred at the impact region in the traditional panels, while part plies of the rear face-sheets split-off in the SMA hybrid panels. The impact performance of the SMA hybrid panels is improved when compared with the traditional panel, the reduction of the delamination area by 48.15% and the increase of the load-bearing threshold by 32.75% are acquired for the hybrid sandwich panel with two layers of SMA fibers in the rear face-sheet.

The shear properties of rock joint control the stability of rock and have an important impact on natural disasters such as landslides and debris flow. In order to study the stress effect and scale effect of shear properties of double saw-tooth rock joint, cement mortar is selected as similar material, a series of mix ratio tests are carried out, and the best mix ratio is obtained. Using rock joint integrated mold and joint panel produced by 3D printing technology, several groups of double saw-tooth joint specimens with different saw-tooth heights, saw-tooth widths, and saw-tooth spacings are made. Under multiple levels of normal stress, direct shear tests of different scale specimens are carried out by self-developed multifunctional rock-soil contact damage test system. Results show that the shear failure modes of double saw-tooth rock joint include couple effect of overriding and cutting off, and cutting off effect, which are mainly controlled by the rock joint morphology and normal stress. Peak shear strength increases with the increase of saw-tooth width and spacing, but the change with saw-tooth height is not obvious. Peak shear strength and peak friction angle of the double saw-tooth rock joint have significant characteristics of stress effect and scale effect.

Concrete with the addition of polypropylene fibres is more cohesive and has better adhesion, deformability and tightness because the fibres “bind” the concrete matrix together and prevent large pores from forming in the concrete mix and limit the formation and spread of shrinkage cracks. Therefore, it can be assumed that polypropylene fibres affect the effectiveness of the concrete cover as a layer protecting steel bars against corrosion. This article presents the results of tests allowing us to estimate the effect of addition of polypropylene fibres on the reduction of reinforcing bars corrosion in concrete caused by the action of chlorides. Evaluation of the degree of corrosion of the reinforcement was analysed using the electrochemical polarisation galvanostatic pulse technique. The use of such a method allowed for the quantitative estimation of the effect of the addition of polypropylene fibre on the reduction of corrosion activity of the reinforcement in concrete.

The cylindrical filament wound composite overwrapped pressure vessels (COPV) with metal liner has been widely used in spaceflight due to their high strength and low weight. After the autofrettage process, the plastic deformation of the metal liner is constrained by composite winding layers, which introduce depressions to the metal liner that causes local buckling. To predict the local buckling of the inner liner with depressions of the pressure vessel after the autofrettage process, a local buckling analysis method for the metal liner of COPV was developed in this article. The finite element method is used to calculate the overall stress distribution in the pressure vessel before and after the autofrettage process, and the influence of local depressions on the buckling is evaluated. The axial buckling of the pressure vessel under external pressure is analyzed. The control equation of the metal liner with depressions is developed, considering the changes in the pressure and the bending moment of the liner depressions and its vicinity during the loading and unloading process. Taking the cylindrical COPV (38 L) with aluminum alloy liner as an example, the effects of liner thickness, liner radius, the thickness-to-diameter ratio, autofrettage pressure, and the length of straight section on the autofrettage process are discussed. The results show that the thickness of the inner liner has the most significant influence on the buckling of the liner, followed by the length of the straight section and the radius of the inner liner, while the autofrettage pressure has the least influence.

To study the influence of basalt fibers on the viscoelastic mechanical properties of asphalt concrete (AC) mixtures, unconfined compressive dynamic modulus tests were performed on styrene–butadiene–styrene (SBS)-modified AC mixtures reinforced with various contents of basalt fibers ranging from 0.2 to 0.5% by weight at five temperatures and six load frequencies, and the dynamic moduli and phase angles of the mixtures were measured. Compared with the test results of the control mixture (with no basalt fibers), the data show that the high-temperature dynamic modulus of the mixtures initially increases and subsequently decreases with increasing fiber content and reaches its maximum value when the basalt fiber content is 0.3%, while the low-temperature dynamic modulus decreases monotonically with increasing fiber content. Furthermore, the phase angle of the mixtures initially decreases and later increases with increasing fiber content and reaches its minimum value when the basalt fiber content is 0.3%. These behaviors indicate that the addition of basalt fiber improves the high-temperature rutting resistance and low-temperature cracking resistance of the SBS-modified AC mixtures. In addition, the results of the wheel rut test exhibit a good correlation with the results of the dynamic modulus test, revealing the reliability of the dynamic modulus test for evaluating the high-temperature rutting resistance of basalt-fiber-reinforced AC mixtures.

The most significant difference between recycled and natural concretes lies in aggregates. The performance of recycled coarse aggregates directly affects the characteristics of recycled concrete. Therefore, an in-depth study of aggregate characteristics is of great significance for improving the quality of recycled concrete. Based on the coarse aggregate content, maximum aggregate size, and aggregate shape, this study uses experiments, theoretical analysis, and numerical simulation to reveal the impact of aggregate characteristics on the mechanical properties of recycled concrete. In this study, we selected the coarse aggregate content, maximum aggregate size, and the aggregate shape as design variables to establish the regression equations of the peak stress and elastic modulus of recycled concrete using the response surface methodology. The results showed that the peak stress and elastic modulus of recycled concrete reach the best when the coarse aggregate content is 45%, the maximum coarse aggregate size is 16 mm, and the regular round coarse aggregates occupy 75%. Such results provide a theoretical basis for the resource utilization and engineering design of recycled aggregates.

A plate used in a medium voltage switch, made by a 25 wt% glass fiber-reinforced polyamide 66 composite filled with flame-retardant red phosphorus (RP) (PA66-GF25 FR (RP)), was injection molded. To satisfy the relatively high dimensional accuracy requirement, a “supporting mold” was used to compensate for the difference between the transverse and longitudinal linear shrinkage of the PA66-GF25 FR (RP). To reduce the internal residual stress caused by the “supporting mold,” hygrothermal conditioning treatments, including boiling water bath at 90–100°C and re-drying at 110°C, were used. To determine the effects of boiling water bath and re-drying on the dimensional accuracy and mechanical properties of the product, three treatment routes were applied. It was found that the route in which the boiling water bath is applied after the “supporting mold” is preferred to ensure the dimensional accuracies and the mechanical properties as a whole. Using a boiling water bath as a hygrothermal conditioning treatment can improve the mechanical properties and increase the dimensional accuracy of the product. In addition, by using the preferred route, re-drying can further improve the tensile, bending, and even impact strength.

In this article, we proposed a novel but simple multilayer resin film infusion-compressive molding (MLRFI-CM) manufacturing process that can harness the resin shear flow to architect hierarchical carbon fiber reinforced polymer (CFRP) composites with tunable 1D nanocarbons orientation. Via this novel process, we demonstrated that the orientation of two typical 1D nanocarbons, namely, the carbon nanotubes (CNTs) and carbon nanofibers (CNFs), can be successfully tuned via altering the infusion time and that the tuning strategy is especially effective toward CNTs. Further, the structure-performance relationships between the electrical conductivity/interlaminar shear strength (ILSS) and filler through-thickness orientation of the hierarchical CFRP composites is explored and compared. In the best case, with only 0.3 wt% of CNTs, the ILSS of CFRP composites revealed an increase of 19.7%, and the through-thickness conductivity demonstrated an increase of 38%.

Bamboo scrimber is a new natural fiber-reinforced composite material in modern industry. In this paper, the tensile creep characteristics of this material were chosen as the object of the study. First, axial tensile fracture experiments were conducted on different test specimens to determine the corresponding strength data. Then six sets of standard tensile creep experiments were conducted under different given stress levels. Finally, the Maxwell constitutive model was applied in fitting the relationship between strain and time. The results showed that the traditional Maxwell viscoelasticity constitutive model will result in some errors in the fitting results, while the combined fractional and Maxwell model can provide much higher accuracy in this study, thus it is more suitable for engineering applications. This paper provides a solid foundation for a better understanding of the mechanism of the bamboo scrimber creep behavior.

This paper presents a new approach to strengthen reinforced concrete structures using natural fiber composites. Natural fibers are often used in civil engineering for thermal or acoustic insulation, but rarely are they employed to strengthen structures. Natural fiber composites are constituted of a matrix based on epoxy adhesive and aligned continuous fiber reinforcements. In this study, we investigate several fibers (carbon, hemp, fiberglass, and linen) in tensile and bending tests. The bending results show twice the magnification of the ultimate bending load in a strengthened specimen. The study also evaluates the stress distribution in the structure. In the case of a beam strengthened by a bonded carbon plate, the functioning of an assembly single lap and the optimal anchor length was determined by analogy. The analytical study describes the shear and peel stresses in the adhesive, composite, and concrete joints, revealing the optimum values of shear stress near the ends of the adhesive joint. The same was observed in concrete. The tests showed the influence of strengthening on the ultimate load and stiffness as well as the concentration of shear stresses at the ends of the adhesive joint.

The paper presents an impact of the addition of industrial machining chips on the mechanical properties of polymer concrete. As an additional filler, six types of industrial waste machining chips were used: steel fine chips, steel medium chips, steel thick chips, aluminium fine chips, aluminium medium chips, and titanium fine chips. During the research, the influence of the addition of chips on the basic parameters of mechanical properties, i.e., tensile strength, compressive strength, splitting tensile strength, and Young’s modulus, was analyzed. On the basis of the obtained results, conclusions were drawn that the addition of chips from machining causes a decrease in the value of the mechanical properties parameters of the polymer concrete even by 30%. The mechanism of cracking of samples, which were subjected to durability tests, was also explored. In addition, it was found that some chip waste can be used as a substitute for natural fillers during preparation of a mineral cast composition without losing much of the strength parameters.

In this article, the ultrasensitive analysis of single-walled boron nitride nanotubes (SW-BNNTs) with an extra attached mass is studied by employing atomistic analysis technique. Numerical examples are carried out for vibration characteristic of SW-BNNT with an extra attached mass. Our results show that the vibration frequencies and magnitudes of SW-BNNT are very sensitive to the extra attached mass. In addition, the influence of length and chirality of SW-BNNT on the vibration frequencies and magnitudes of SW-BNNT with an extra attached mass are also examined in detail. This investigation indicates that SW-BNNTs have a great potential in the field of sensor technology.

The purpose of this study was to solve the chloride corrosion damage problems of the rebar in reinforced concrete structures under the chloride environment. The effects of 1.0% triethanolamine (abbreviated as 1.0% TEA), 1.0% Ca(NO2)2, and 0.5% TEA + 0.5% Ca(NO2)2 (abbreviated as 1.0% composite corrosion inhibitor) on the electrochemical performance and modification mechanism of the mortar specimens were investigated by combining macro experiment and microanalysis. The results showed that the electrode potential of the rebar was effectively improved by incorporating the 1.0% composite corrosion inhibitor. This composite corrosion inhibitor displayed the ability to stabilize the electrode potential of the rebar; it also formed a passive film on the surfaces of the rebar, protected the rebar from chloride attack, and achieved satisfactory electrochemical performance. In addition, it could also effectively improve the strength of the mortar specimens and possessed the strong ability to bind chloride ions, thus signifying that it could promote cement hydration and accelerate the formation of cement to form AFt crystals. Therefore, the results of this investigation confirmed that this composite corrosion inhibitor could be effectively used in practical engineering to prevent the corrosion of reinforced concrete structures.

With the popularity of stereo printing technology, 3D printers are widely used in industry, manufacturing, medicine, and other industries to quickly manufacture small devices. Before 3D printing, it is necessary to plan the printing path. Unreasonable printing path will not only increase the time consumption of printing products, but also cause printing failure due to the accumulation of stress and deformation in the printing process. In order to overcome the superimposed stress and deformation in the process of printing thin-walled complex devices, this article introduces the idea of balanced stress based on the basic damage of the path planning based on the potential field method. In the printing process, the ring path, island path and cross path are added to overcome the stress deformation phenomenon and improve the printing quality. Finally, the 3D printer is used to manufacture thin-walled complex devices, and the feasibility of the balanced potential field method is verified by physical comparison.

The paper presents studies performed on polymer-cementitious composite made of epoxy resin coating modified with aggregate and cementitious substrate. Epoxy resin is a perfect material that can be used to protect cementitious materials. According to its manufacturer, it can be mixed with fine aggregate. Coarse aggregate made of building demolition wastes is mostly utilized in concrete mixtures or road structures. Fine aggregate is not widely used. Therefore, the novelty of this research was the utilization of recycled fine aggregate (RFA) in epoxy resin coatings. Natural fine aggregate (NFA) was also used as an extender in the coating. The natural aggregate in the coating was partially replaced with recycled aggregate in amounts of 0, 20, 40, 60, 80, and 100% of its weight. Sixteen specimens of polymer-cementitious composites were prepared for the flexural tensile strength test, and thirty-two specimens for the compressive strength test. The macroscale tests were performed after 35 days of curing (28 days – cementitious substrate, and 7 days – epoxy resin). The results show that the epoxy resin coating does not affect the flexural tensile and compressive strength of the analyzed composites. Moreover, the type of aggregate used in the coating does not have a significant impact on the measured properties of polymer-cementitious composites. Economic analysis was performed in order to estimate the cost of the natural and RFAs used in epoxy resin coatings. The calculations show that a higher amount of RFA should be used to increase savings.

The structure and behaviour of two gypsum composites after exposition to elevated temperatures were investigated. The silica sand and fine basalt aggregate were used as solid fillers. The changes in structure and composition at temperatures from 50 to 1,000°C were investigated by scanning electron microscopy and X-ray diffraction together with the size and strength of the samples and their pore size distribution. The structure of gypsum matrix changed significantly at 1,000°C in both composites, while the aggregate particles were not changed. It was found that even if the silica sand is considered as less suitable filler at high temperatures because of its volume changes, the gypsum with sand performed better than gypsum with basalt at the highest temperatures, because the shrinkage of the gypsum matrix was compensated by the increase in the volume of aggregate. The final volume change at 1,000°C was 3.5% in composite with silica sand and 6.8% in composite with basalt. The residual compressive strength of both composites was about 9.4%. No cracks appeared in the samples and no spalling was observed.

Characterization of shear behavior in composite materials remains a not fully solved problem. In the last fifty years, many different approaches have been proposed to solve this problem (rail shear, thin-walled tube torsion, off-axis tensile, ±45° tensile, Arcan, Iosipescu, asymmetric four-point bend, plate twist, v-notched rail shear, off-axis flexural, and shear frame), although none of these approaches have achieved an unquestionable solution. For this reason, proposals of alternative methods and comparison between different experimental techniques are of interest. In the present work, the use of cruciform samples with the fiber oriented at 45° with respect to the load directions, and subjected to tension-compression (creating a pure shear stress state at the central part of the samples), is studied. The experimental results of the cruciform samples have been compared with the off-axis tests (with the fiber at 10°) for the same material (AS4/8552), finding a good agreement between the shear experimental curves, especially at the initial part of the curve, where the shear modulus is calculated. Nevertheless, the shear strength value obtained by means of the cruciform specimen has shown to be significantly lower than that obtained using the off-axis test. A Finite Element numerical model of the cruciform specimen has been developed to analyze the stress field of the samples. Numerical results have shown that there is a central area of the cruciform specimens where a pure and uniform shear stress state is developed, which is suitable for the evaluation of the shear constitutive law of the material. It has been observed that there is a (σ 22) stress concentration in the transition between the straight and curved parts of the boundary geometry of the samples, which explain some premature failures of the samples. This premature failure could be avoided with tabs extended up to the beginning of the central part of the sample.

The objective of this work is to improve the structural characteristics of hollow glass microsphere (HGM) filled epoxy syntactic foam composites with little voids content and improved HGM dispersion in the composite. A modified degassing technique has been introduced during resin casting process of the HGM filled syntactic foam composites. The effect of HGM content volume fractions (5–25%) on the degassing techniques was examined. The syntactic foam composites were characterized by analysing structural morphology using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy(TEM), and density measurements (theoretical and experimental). Less than 5% void content has been achieved in this study. This resulted in improved tensile and dynamic mechanical properties (DMA).

In this study, the flexural bearing capacity and failure mechanism of carbon fiber-reinforced aluminum laminate (CARALL) beams with a double-channel cross-section and a 3/2 laminated configuration were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°]3 and [45°/0°/−45°]3) were fabricated using the pressure molding thermal curing forming process. The double-channel CARALL beams were subjected to static three-point bending tests to determine their failure behaviors in terms of ultimate bearing capacity and failure modes. Owing to the shortcomings of the two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for the ABAQUS/Explicit solver and an analysis algorithm were established to obtain a progressive damage prediction of the CFRP layer using the three-dimensional Hashin failure criterion. Various failure behaviors and mechanisms of the CARALL beams were numerically analyzed. The results indicated that the numerical simulation was consistent with the experimental results for the ultimate bearing capacity and final failure modes, and the failure process of the double-channel CARALL beams could be revealed. The ultimate failure modes of both types of double-channel CARALL beams were local buckling deformation at the intersection of the upper flange and web near the concentrated loading position, which was mainly caused by the delamination failure among different unidirectional plates, tension and compression failure of the matrix, and shear failure of the fiber layers. The ability of each fiber layer to resist damage decreased in the order of 90° fiber layer > 0° fiber layer > 45° fiber layer. Thus, it is suggested that 90°, 0°, and 45° fiber layers should be stacked for double-channel CARALL beams.

Interfacial degradation is the main reason for deterioration of mechanical properties of composites in hydrothermal environments. In this study, the effect of the interphase on water diffusion in two types of unidirectional continuous carbon fiber-reinforced polyamide 6 (CF/PA6) composites is investigated through experimental measurements, theoretical analysis, and numerical simulation. The moisture diffusion coefficient of composite at different environmental temperatures is characterized by water immersion tests for analyzing the barrier and accelerating effects of the interphase layer. Based on the experimental results, the three-phase Halpin–Tsai model is derived and validated, and then the critical diffusivity is obtained to quantify the interfacial effect during the diffusion process. To further validate the present three-phase Halpin–Tsai model, the stable and transient finite element models of moisture diffusion are developed. It is found that the critical diffusivity coefficient of the interphase for the CF/PA6 composite system is 7.31 times higher than that of the matrix.

In this paper effects of material constructions on natural frequencies and critical aerodynamic pressures are investigated. It is assumed that the rectangular plate is made of a polymeric matrix reinforced with graphene nanoplatelets or carbon nanotubes. A general closed analytical method of solution is presented. It is demonstrated that three parameters define entirely the location of the critical flutter pressure. The influence of material properties and transverse shear effects is characterized by a set of multipliers. They can be easily adopted in design procedures.

A modified vertical braiding machine and closed annular axis mandrels with a special-shaped cross section were used to braid annular axis preforms under four different technical parameters. After measuring the braiding angles and yarn spacing of the braided preform in different areas of the mandrels, it was found that the braiding angle increased by 20.9% and the yarn spacing decreased by 19.8% when the speed of the yarn carrier was doubled. The braiding angle decreased by 31.1% and the yarn spacing increased by 28.6% when the rotation speed of the mandrels was doubled. The results show that the rotation speed of the mandrel has a slightly greater influence on the braiding angle and the yarn spacing. By using the modified braiding machine to braid the annular axis preforms, multi-layer continuous braided preforms can be achieved on compact equipment. And the structure of the annular axis braided preforms can be changed by changing the technical parameters.

In-situ TiB2 particles can be synthesized via the salts-Al reaction by adding mixed K2TiF6 and KBF4 (Ti/B=1/2) salts into Al melt. In this research, a novel electroslag melting technology was proposed to synthesize TiB2 particles by the salts-Al reaction in order to reduce the reaction time period and purify the melt of composite. The effects of current of electroslag melting on the synthesis of TiB2 particles and mechanical properties of composite were investigated. The results showed that TiB2 particles could be in-situ synthesized by electroslag melting at 600 A for 15min. Compared with 60 min at 850°C of traditional LSM method, the efficiency of preparation was greatly improved. In addition, the dispersion of TiB2 particles in the composite prepared by electroslag melting was improved, meanwhile the non-metallic inclusions in the composite was reduced. The values of YS, UTS and El pct of composite prepared by electroslag melting were higher than that of the composite prepared by traditional LSM method.

Poly-lactic acid based biocomposite strengthened with magnesium alloy wires (Mg wires/PLA composite) is prepared for bone fixation implantation. The influence of wire content and load mode on the degradation performances of the composite and its components is studied. The result suggests the degradation of Mg wires could slow down the pH decrease originated from the degradation of PLA, while a relatively high wire content contributes to descend the degradation rate of Mg wire in the composite. Dynamic load significantly promotes the mechanical loss of the specimens. After 30 days immersion, the Sb retention is about 65%, 52% and 55%, respectively for pure PLA, the composite at 10 vol% and 20 vol% under dynamic load, comparing to 75%, 70% and 72% under no load. Moreover, dynamic load could further mitigate the degradation of Mg wires by increasing convective transport of acidic products out of the composite.

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 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.

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.

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.

The Pb(Ni1/3Nb2/3)O3-Pb(Zr x Ti1−x )O3 (PNN-PZT) piezoelectric ceramics with CuO and LiBiO2 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.% LiBiO2 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.

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]2s 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.

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.

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)

In this study, the effective elastic modulus (Ec ) 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 (MFf ) 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 MFf , but was relatively low for interphase regions exhibiting a gradient. The results show that interphase parameters must be considered carefully when predicting Ec using the FE model.

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.

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, 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 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.

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 - TiB2 (Titanium Diboride) composites with different amounts of reinforcement (5, 7.5 and 10 wt.%) were produced by the exothermic reaction of halide salts K2TiF6 and KBF4 added in 120% excess to the stoichiometric ratio with molten AA7010.The effect and dispersion of TiB2 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 TiB2 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% TiB2 shows better results compared with matrix alloy and other concentrations of reinforcements.

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.

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.