Physical dispersion state and fluorescent property of Eu-complex in the Eu-complex/silicon rubber composites

The fluorescent complex Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, MA=Maleic an- hydrider） was synthesized and characterized with elemental analysis, infrared spectrum （IR）, scanning electron microscope （SEM）, X-ray Diffraction（XRD）, differential scanning calorimetry（DSC）, and fluorescent measurement. To explore the effect of different physical dispersion state of Eu-complex on the fluorescent property of the Eu-complex/silicon rubber composites, various quantifies of Eu（TTA）2（phen） （MA） were mixed with silicon rubber （SIR） and peroxide to form uncured composites. These composites were vulcanized to obtain cured Eu-complex/SiR composites at 250 ℃, which was higher than the melting-point of Eu-complex. The SEM, XRD, DSC, and the fluorescent measurement of these composites showed that both the complex molecules dispersed in the silicon rubber during the melting process and the parent Eu-complex particles had positive effects on fluorescent property, whereas the re-crystallized Eu-complex particles and the aggregating complexes formed during the melting-process had negative effects on fluorescent property. For the uncured composites, their fluorescent intensities almost did not change with the increasing amount of Eu-complex. Furthermore, for the composites with small content of Eu-complex, their fluorescent intensities decreased significantly after curing, and this difference in fluorescent intensity became smaller as the content of Eu-complex increases.

In vitro study of the PLLA-Mg_(65)Zn_(30)Ca_(5)composites as potential biodegradable materials for bone implants

PLLA-magnesium composites have been widely investigated as potential biodegradable materials for bone implants.Lower/higher corrosion resistance of the crystalized/amorphous magnesium alloys allows tailoring of biodegradability rate.In this work,the amorphous Mg_(65)Zn_(30)Ca_(5)was investigated versus traditional crystalized Mg_(65)Zn_(30)Ca_(5),and a PLLA-Mg_(65)Zn_(30)Ca_(5)composite has been successfully fabricated using hot injection process.Furthermore,the high corrosion resistance of the amorphous Mg_(65)Zn_(30)Ca_(5)prevented the high alkalization and deterioration of mechanical strength.In addition,the high Zn content intended to improve the glass forming ability,also enhances the anti-bacterial property of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite.The remarkable performance of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite shows its promising application in bone repair and tissue regeneration.

Flexural Stress Homogenization Effects of Interfacial Transition Layers in Modified ZrB2-Al2O3/Epoxy Composites

The effect of interfacial modification on flexural strength of epoxy composites filled with modified ZrB2-Al2O3 composite fillers was investigated in order to explore the stress distribution of modified composites under external load. The mechanical performance of epoxy composites filled with 0 vol%, 1 vol%, 3 vol% and 5 vol% unmodified and modified ZrB2-Al2O3 fillers was characterized by three point bending(TPB) tests. The fracture surfaces of epoxy composites were observed by scanning electronic microscope(SEM). The results showed that the epoxy composite reinforced by 1 vol%modified fillers exhibited the optimal mechanical performance. According to the Von Mises stress contours simulated by finite element models(FEM) and the SEM images, it was shown that the modified ZrB2-Al2O3 multiphase fillers could homogenize the stress in the epoxy composites due to the transition effect resulted from the interfacial modification layers on the surfaces of multiphase fillers. It contributed to the improvement of mechanical performance of epoxy composites further.

Dynamic Mechanical and Thermal Properties of Cross-linked Polystyrene/Glass Fiber Composites

Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane （VTES）, vinyl trimethoxysilane （VTMS） and γ-methacryloylpropyl trimethoxysilane （MPS）. The treated glass fibers were analyzed by fourier transform infrared spectroscopy （FTIR）. Dynamic mechanical thermal analysis （DMTA） and thermo-gravimetric analysis （TGA） were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy （SEM）. The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.

Outstanding Impact Resistance of Post-Consumer HDPE/Multilayer Packaging Composites

New recycling alternative for multilayer films was successfully presented. Food packaging formed from different materials is difficult to recycle. The use of aluminum, glass, paper, paints, varnishes, and other materials in the rolling processes from plastic packaging is intended to optimize the efficiency of packaging. Nevertheless, these materials prevent the recycling of packaging because they become contaminants to the recycling process. Food multilayered packaging containing poly (ethylene terephthalate) PET, poly (ethylene) PE and aluminum was used as filler in the preparation of composites with post-consumer high density polyethylene matrix. Composites containing up to 50 wt% of filler were feasible to prepare, allowing the obtention of a material with varied mechanical and thermal properties. This feature allows the preparation of composites suitable for specific application. The addition of multilayer matter in the polyethylene matrix provided a material with excellent mechanical properties such as higher tensile impact strength (148 J/m) and elasticity (350 MPa) as compared to pure polyethylene (40 J/m and 450 MPa).

Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

Multiphysics Based Simulation of Damage Progression in Composites

The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. Although a clear understanding has been established for initiation, growth and accumulation of damage, it is still unclear when and how the interactions of these local events lead to the development of a “critical” fracture path resulting in a sudden change of global properties and possible rupture. In the present paper, we simulate damage development in a neat polymeric resin using X-FEM analysis, and conduct concomitant dielectric response analysis with a COMSOLTM simulation model to study the collective defect structure as it develops in a model system. Our studies reveal inflection points in the predicted global dielectric response vs. strain that are related to changes in local damage growth rates and modes that clearly indicate impending fracture and capture the progressive change in material state.

Static Crack Propagation of Carbon Nanotube through Non-Bonded Interface of Nanocomposites

This study presents an analytical shear-lag model to illustrate the interface crack propagation of carbon nanotube (CNT) reinforced polymer-matrix composites (PMCs) using representative volume element (RVE). In the model, a 3D cylindrical RVE is picked to present the nanocomposite in which CNT/polymer chemically non-bonded interface is taken into consideration. In the non-bonded interface, the stress transfer of CNT is generally considered to be controlled by the combined contribution of mechanical interlocking, thermal residual stress, Poisson’s contraction and van der Waals (vdW) interaction. Since CNT/matrix interface becomes debonded due to crack propagation, vdW interaction which is a function of relative radial displacement of the CNT/matrix interface makes the modeling of the interface tricky and challenging. In order to solve this complexity, an iterative approach is proposed to calculate the vdW interaction for debonded CNT/matrix interface accurately. The analytical results aim to obtain the characteristics load displacement relationship in static crack propagation for CNT reinforced PMCs.

Dielectric Properties and a.c. Conductivity of Epoxy/Alumina Silicate NGK Composites

Alumina silicate powder which is extracted from the obsolete spark plug NGK (insulator part as a filler) has been used to produce epoxy/alumina silicate composite. The dielectric behavior of the composite materials (epoxy resin-alumina silicate NGK) is analyzed as a function of the filler content, temperature and frequency. AC conductivity and impedance are also studied. The results show that the permittivity, dielectric loss and loss tangent for all composites increase with increasing alumina silicate NGK filler content.

Surface Functionalized Carbon Nanofibers and Their Effect on the Dispersion and Tribological Property of Epoxy Nanocomposites

Surface functionalization of carbon nanofibers（CNFs） was carried out, i e, CNFs were firstly oxidized and then the surface was silanized by 3-Aminopropyltriethoxysilane（APTES） via an assembly method. A new kind of high wear resistance s-CNFs/epoxy composite was fabricated by in-situ reaction. FTIR spectroscopy was used to detect the changes of the functional groups produced by silane on the surface of CNFs. The tribological properties and microstructures of modified and unmodified CNFs/epoxy composites were studied, respectively. The expremental results indicate that APTES is covalently linked to the surface of CNFs successfully and improves the dispersion of CNF in epoxy matrix. The friction coefficients and the wear rates of s-CNFs/epoxy composites are evidently lower than those of u-CNFs/epoxy composites under the same loads. Investigations also indicate that abrasive wear is the main wear mechanism for u-CNFs/epoxy composite, with slight adhesive wear for s-CNFs/epoxy composite under the same sliding wear condition.

Structure and Properties of Natural Rubber/Zinc Disorbate Composite

The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction(XRD) and Fourier-transform infrared spectroscopy(FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature(Tg) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and Tg shifted towards to higher temperature.

Significantly enhancing fracture toughness of epoxy composite with promisingγ-FeOOH@Fe_(2)O_(3)hybrid nanoparticles by magnetic field assistance

The toughening of epoxy resin(EP)and the interlaminar toughening of carbon fiber reinforced composite(CF/EP)laminates have been widely concerned.In this work,the needle-likeγ-FeOOH nanoparticles were prepared by liquid phase deposition-air oxidation method,and then were calcined under different conditions to obtainγ-FeOOH andγ-Fe_(2)O_(3) hybrid nanoparticles(γ-FeOOH@Fe_(2)O_(3)).Effect of calcination condition ofγ-FeOOH@-Fe_(2)O_(3) and magnetic field assistance on fracture toughness(KIC)of EP was systematically investigated.Then the selectedγ-FeOOH@Fe_(2)O_(3) with the best toughening effect were used to improve the mode I interlaminar fracture toughness(GIC)of CF/EP laminate.The resultingγ-FeOOH@Fe_(2)O_(3) have a length of around 1μm,a diameter of around 100 nm and the Ms of 8.99–45.96 emu/g.After calcinated at 250℃ for 1 h,theγ-FeOOH@Fe_(2)O_(3) containing 24 wt%FeOOH and 76 wt%Fe_(2)O_(3) achieved the best toughening effect.Under a magnetic field of 0.09 T,the KIC of theγ-FeOOH@Fe_(2)O_(3)/EP composite(2.45 MPa m^(1/2)) is 81.7%and 66.7%higher than that of neat epoxy and the composite without magnetic field induction,respectively.Furthermore,the GIC of theγ-FeOOH@Fe_(2)O_(3)/CF/EP composite(0.914 kJ/m^(2)) is also significantly increased by 88.8%and 51.8%compared to that of CF/EP and the corresponding composite without magnetic field induction,respectively.

Bridging Effect and Efficiency of Partly-Cured Z-pin Reinforced Composite Laminates

To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the quantitative relationship between the maximum bridging force and Z-pin diameter,embedded length,interfacial shear strength and tensile strength is acquired.The Z-pin″bridging law″test and Z-pin tensile test are carried out to study the effect of Z-pin′s curing degree on bridging effect,and the bridging efficiency is defined to evaluate the reinforcement effect of Z-pin.The modeⅠinterlaminar fracture toughness(G_(ⅠC))is measured by the double cantilever beam test.The experimental results show that Z-pin′s co-curing with laminate matrix can improve the bridging force significantly and the fitting results show a linear relationship between Z-pin curing degree and interfacial shear strength.The three-dimensional images of the surface of pullout Z-pins indicate that the failure mode changed from totally interfacial debonding to a mixed mode.Finally,the reinforcement by partly-cured Z-pin can be used to further enhance the interlaminar toughness.Compared with completely-cured Z-pin,G_(ⅠC) of Z-pin with 67.6% curing degree increases by 47.0%.

Data-Driven Exploration of Polymer Processing Effects on the Mechanical Properties in Carbon Black-Reinforced Rubber Composites

The performance and corresponding applications of polymer nanocomposites are highly dominated by the choice of base material,type of fillers,and the processing ways.Carbon black-filled rubber composites(CRC)exemplify this,playing a crucial role in various industries.However,due to the complex interplay between these factors and the resulting properties,a simple yet accurate model to predict the mechanical properties of CRC,considering different rubbers,fillers,and processing techniques,is highly desired.This study aims to predict the dispersion of fillers in CRC and forecast the resultant mechanical properties of CRC by leveraging machine learning.We selected various rubbers and carbon black fillers,conducted mixing and vulcanizing,and subsequently measured filler dispersion and tensile performance.Based on 215 experimental data points,we evaluated the performance of different machine learning models.Our findings indicate that the manually designed deep neural network(DNN)models achieved superior results,exhibiting the highest coefficient of determination(R^(2))values(>0.95).Shapley additive explanations(SHAP)analysis of the DNN models revealed the intricate relationship between the properties of CRC and process parameters.Moreover,based on the robust predictive capabilities of the DNN models,we can recommend or optimize CRC fabrication process.This work provides valuable insights for employing machine learning in predicting polymer composite material properties and optimizing the fabrication of high-performance CRC.

Flexible PVA/BMIMOTf/LLZTO composite electrolyte with liquid-comparable ionic conductivity for solid-state lithium metal battery

Poly(vinyl alcohol)(PVA)/1-butyl-3-methylimidazolium trifluoromethanesulfonate(BMIMOTf)/Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)solid-state composite electrolyte(SSCE)membranes were synthesized for solid-state lithium metal battery application.The garnet-type LLZTO nanoparticles were surface-coated with the polydopamine layer of 8-10 nm thickness to enhance the dispersion status of LLZTO particles in the PVA matrix.The hydrophilic BMIMOTf ionic liquid(IL)was added along with LLZTO nanoparticles to enhance the ionic conductivity and electrochemical stability of the SSCE membranes.The synthesized composite electrolyte membrane containing 7 wt%of LLZTO and 60 wt%of BMIMOTf showed the outstanding Li+conductivity of 2×10^(-3)S cm^(-1)and the lithium transference number of 0.76 at room temperature in the firm and flexible solid state with the tensile strength of 8 MPa.Such a high single ion conduction characteristic led to the quite low interfacial resistance of 39Ωbetween the composite electrolyte and the lithium anode.Owing to these superior properties of composite membranes,the LiFePO_(4)|SSCE|Li cell exhibited an excellent discharge capacity of 165 mAh g^(-1)at 0.2 C,maintaining the coulombic efficiency of 98%after 100 cycles at room temperature.

Structure, Energy Band Gap and Electrical Conductivity of Tapioca/Metal Oxide Composite

A natural polymer composite is the main choice to replace composites from petroleum derivatives. A composite is formed in two or more phases （i.e., organic and inorganic phases）. A composite that has specified energy band gap, electrical conductivity, and tensile strength can be used as semiconductor material. The objective of this research was to study the effect of production methods, concentration and type of metal oxide filler （TiO2, A1203, Fe203, and ZnO） on structure, energy band gap, and electrical conductivity of composites. Composites were prepared using a melt intercalation process with tapioca as a matrix and addition of 1%, 3%, 5o and 7% filler concentrations, and sonication processing time in interval of 40, 50, and 60 min. Structure and morphology of the composite were analyzed using FT-IR, XRD, SEM, and TEM. UV-vis was used to measure the energy band gap while electrical conductivity was measured using a potentiostat through determination of resistivity. In addition, tensile strength and elongation were measured by ASTM 822-02. The energy band gap of the tapioca/metal oxide composite was between 4.9-1.62 eV. Electrical conductivity showed a percolation thresholds for concentrations of 3%-5% TiO2, A1203, and Fe203 and 7% ZnO. The tapioca/ZnO composite with 5% ZnO and 50 min of processing time showed a maximum tensile strength of 74.84 kgf/cm2, 6% elongation, 1.27 - 10^-7ohm^-1cm^-1 electrical conductivity and energy band gap of 3.27 eV. The characteristics described show that the tapioca/metal oxide composite can be used as a semiconductor material.

Development of EPDM composites reinforced by CNTs@SiO_(2)for thermal protection systems of aerospace propulsion:Significant improvement in oxidation and ablation resistance properties

Carbon Nanotubes(CNTs)reinforced Polymer-Matrix Composites(PMCs)is widely used as insulation materials in thermal protection system of aerospace propulsion.However,CNTs are prone to oxidation and have high thermal conductivities,which makes it difficult to improve the ablation resistance of insulation materials that contain CNTs.SiO_(2)was encapsulated onto the surface of CNTs(CNTs@SiO_(2)),which were then added to Ethylene Propylene Diene Monomer(EPDM)rubber to prepare the insulation materials.Thermogravimetric analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ablation.Additionally,scanning electron microscopy was performed to analyze their microstructures.Results revealed that the addition of CNTs@SiO_(2)could visibly reduce the effects of hot corrosion and ablation on insulation materials.The C-CNTs@SiO_(2)-1 formulation had the best ablative resistance.Further,compared with the unencapsulated formulation(C-CNTs-10),the C-CNTs@SiO_(2)-1 formulation reduced the line ablation rate by 51%to 0.0130 mm/s after oxygen-acetylene experiments.Lastly,the ablation mechanism was investigated based on the effects of the CNTs@SiO_(2)additive on their properties.Thus,the improvement in ablation performance may be attributed to CNTs@SiO_(2)-induced decreases in thermal conductivity,improvement in the hot corrosion resistance in the char layer,and changes in the microstructure.

Laser ablation mechanism and performance of glass fiber-reinforced phenolic composites:An experimental study and dual-scale modelling

Both experimental and simulation approaches were employed to investigate the laser ablation mechanism and performances of Glass Fiber Reinforced Phenolic Composites(GFRP).During the ablation process,the difference in thermal conductivities of the glass fibers and the resin matrix as well as their discrepant physical and chemical reactions form a conical ablation morphology.The formation of a residual carbon layer effectively mitigates the ablation rate in the thickness direction.A higher power density results in a faster ablation rate,while a longer irradiation time leads to a larger ablation pit diameter.To account for the variation in thermal conductivity between the fiber and resin,a macro-mesoscale model was developed to differentiate the matrix from the fiber components.Finite element analysis revealed that laser irradiation leads to phenolic decomposition,glass fiber melting vaporization,and residual carbon skeleton evaporation.The dual-scale model exhibits precise prediction capabilities concerning the laser ablation process of GFRP,and its accuracy is confirmed through the comparison of simulation and experimental results for the GFRP laser ablation process.This model provides a feasible method for performance evaluation and lifetime prediction of GFRP subjected to continuous wave laser irradiation.

Integration of piezoelectric transducers(PZT and PVDF)within polymer-matrix composites for structural health monitoring applications:new success and challenges

This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile loadings.The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings.SHM is performed acquiring the electrical capacitance variation of the embedded transducers.To study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves.Results confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working domain.PZT capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness.The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.

CF/GF混杂增强环氧树脂复合材料的高载动态黏弹特性

采用高载动态热机械分析仪EPLEXOR500对T300/S-2混杂纤维增强环氧树脂复合材料的动态黏弹特性进行了分析,考察了静态载荷、动态载荷对其储能模量、损耗模量和损耗角正切的影响,并研究和对比了不同载荷水平下混杂比以及混杂方式对动态黏弹性参数的影响规律。结果表明:不同混杂比复合材料的储能模量均随动态载荷的增大而降低,随静态载荷的增大而增大,损耗模量和损耗角正切则随两种载荷的增大而降低。高载荷下混杂复合材料的储能模量仍较好地符合“复合梁理论”。动载扫描模式下,损耗角正切随混杂比的变化基本符合“混合定律”,夹芯混杂复合材料的储能模量远高于层间混杂复合材料,且损耗角正切也比层间混杂时大;但在静载扫描模式下则是层间混杂复合材料的损耗角正切更大。