Gypsum-based Silica Gel Humidity-controlling Composite Materials:Preparation,Characterization,and Performance

Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.

Research Progress of Carbon-Silicone Composite Materials

Silicone is a kind of polymer material with high cross-linked structure,which is com-posed by Si-O-Si main chain.Due to the special molecular chain structure,silicone mate-rials are characterized by oxidation resistance,aging resistance,high and low temperature resistance and chemical corrosion resistance.Moreover,silicone materials have process-able properties,simple forming process,good mechanical property,non-toxic and pollution-free.Therefore,silicone has been widely concerned by researchers at home and abroad.In this paper,the main research progress and application directions of carbon-silicone composite at home and abroad in recent years are reviewed.

Deformation Characteristics and Mechanical Properties of Ti/Al Bimetallic Composite Materials Fabricated by Wire Plus Arc Additive Manufacturing

We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After compression deformation,allαstructures of titanium were compacted with the emergence of Widmanstatten structures.Coarsened coloniesαof titanium were elongated and waved along the original growth direction,resulting in anisotropy of grains.Pores and Ti/Al intermetallic compounds of aluminum are significantly decreased after hot compression.Meanwhile,a good bonding interface between titanium and aluminum is obtained after hot compression,and the element diffusion is more intense.In addition,the mechanical properties and fracture behaviors of Ti/Al composite material with different clad ratio that is defined as the ratio of the thickness of titanium to that of the Ti/Al composite material are investigated by uniaxial tensile test.The experimental results show that the ultimate tensile strength of Ti/Al composite material is between that of single deposited titanium and aluminum,while the elongation of Ti/Al composite material with low clad ratio is lower than that of single aluminum due to the metallurgical reaction.As the clad ratio increases,the two component layers are harder to separate during deformation,which is resulted from the decrease of the inward contraction stress of three-dimensional stress caused by necking of aluminum.This work may promote the engineering application of Ti/Al bimetallic structures.

Influence of Some Plant Fibers on the Mechanical Performance of Composite Materials

This work focused on the search for biobased materials capable of being used in road techniques as soil inclusions, and on studying the influence of their incorporation on the characteristic parameters of pavement layers. To this end, pineapple, cyperus and imperata plant fibers, due to their endemic availability, were used as reinforcement on sourced materials, notably bar soil, lateritic gravel and silty sand. Complete identification and mechanical tests (Proctor and CBR) were carried out on materials in their natural state (soil) and on composite materials (soil + plant fibers) in the laboratory to determine their classification in road geotechnics, their compaction parameters and their mechanical behavior. Firstly, the various types of 2.5 cm long fibers were incorporated into the different types of soil at mass contents of 1% and 2%. This part of the study showed that the pineapple fiber composite incorporated into class A2 bar soil offered the best results, with a 38% gain in CBR index compared with the natural soil. Pineapple fibers incorporated at 1% in lateritic gravel raise the CBR value of the reinforced soil to 10% of the CBR value of the natural soil and to 7% for silty sand.

Enhanced microwave absorption property of silver decorated biomass ordered porous carbon composite materials with frequency selective surface incorporation

Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing performance,silver coated porous carbon(Ag@PC)is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork.Phase compositions,morphological structure,and microwave absorption capability of the Ag@PC has been explored.Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork,which accelerates graphitization process of the amorphous carbon.The Ag@PC composite without adding polyvinyl pyrrolidone(PVP)exhibits higher dielectric constant and better EM wave dissipating capability.This is because the larger particles of Ag give rise to higher electric conductivity.After combing with frequency selective surface(FSS),the EM wave absorbing performance is further improved and the frequency region below-10 d B is located in8.20-11.75 GHz,and the minimal reflection loss value is-22.5 dB.This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.

A two-scale method for identifying mechanical parameters of composite materials with periodic configuration

In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefly given for two-scale analysis （TSA） of the composite materials. And then a two-scale computation formulation of strains and stresses is developed by displacement solution with orthotropic material coefficients for three kinds of such composites structures, i.e., the tension column with a square cross section, the bending cantilever with a rectangular cross section and the torsion column with a circle cross section. The strength formulas for the three kinds of structures are derived and the TSM procedure is discussed. Finally the numerical results of stiffness and strength are presented and compared with experimental data. It shows that the TSM method in this paper is feasible and valid for predicting both the stiffness and the strength of the composite materials with periodic configuration.

The New Technology of Composite Materials Repairing by Light Wave

The repairing of damaged composite materials becomes a hot research subject in the late 1990s.In this paper a new technology of repairing composite materials is given on the basis of our previous research.The light wave of 675nm transmitted by optical fiber is used as repairing light source,special repairable adhesive which can be stimulated by the light is adopted.By comparing the stiffness of the composite material before and after being damaged,it can be concluded that the mechanical property will not be changed with the feasible repairing technology.

Intercalation Assembly, Characterization and Luminescent Properties of Novel Supramolecular Composite Materials, Tb(Ⅲ) Complex with Tetrapodal Ligand-Montmorillonite

Two kinds of Tb（ Ⅲ ） complexes with tetrapodal ligand, [TbL（NO3）]^3＋ and [TbL]^3＋ （L： 1,1, 1＇, 1＇-tera （ 2-pyridinecarboxylester ）-di （ trimethylpropane）） were intercalated into the interlayer space of montmorillonite （MT） by ion exchange and coordination reaction of L with the Tb^3＋ ion existing in the interlayer space of Tb-MT respectively. The obtained luminescent supramolecular composite materials, [ TbL （NO3） ]^2＋-MT and [TbL]^3＋-MT were characterized by elemental analysis, XRD, FT-IR, UV-vis and thermal analysis. At the same time, the luminescent properties of the materials were also studied. The results show that the intercalated materials with regular layered structure, good thermal stability and the interlayer spacing （d001） approximates to the size of the complex ions which are located in the interlayer space of MT in the form of a monolayer.

Synthesis and analysis of new humidity-controlling composite materials

Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.

Multi-scale Modeling of the Effective Chloride Ion Diffusion Coefficient in Cement-based Composite Materials

N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone （ITZ） between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself. For the convenience of applications, the mortar and concrete were considered as a four-phase spherical model, consisting of cement continuous phase, dispersed aggregates phase, interface transition zone and their homogenized effective medium phase. A general effective medium equation was established to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure. During calculation, the tortuosity （n） and constrictivity factors （Ds/Do） of pore in the hardened pastes are n^3.2, Ds/Do=l.Ox 10-4 respectively from the test data. The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results; The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.

Micromanufacturing of composite materials:a review

Composite materials exhibit advantages from the combination of multiple properties,which cannot be achieved by a monolithic material.At present,the use of composite materials in miniaturized scale is receiving much attention in the fields of medicine,electronics,aerospace,and microtooling.A common method for producing miniaturized composite parts is micromanufacturing.There has been,however,no comprehensive literature published that reviews,compares,and discusses the ongoing micromanufacturing methods for producing miniaturized composite components.This study identifies the major micromanufacturing methods used with composite materials,categorizes their subclasses,and highlights the latest developments,new trends,and effects of key factors on the productivity,quality,and cost of manufacturing composite materials.A comparative study is presented that shows the potential and versatility associated with producing composite materials along with possible future applications.This review will be helpful in promoting micromanufacturing technology for fabricating miniaturized products made of composite materials to meet the growing industrial demand.

Acoustic Response and Micro-Damage Mechanism of Fiber Composite Materials under Mode-Ⅱ Delamination

Realizing the accurate characterization for the dynamic damage process is a great challenge. Here we carry out testing simultaneously for dynamic monitoring and acoustic emission （AE） statistical analysis towards fiber composites under mode-Ⅱ delamination damage. The load curve, AE relative energy, amplitude distribution, and amplitude spectrum are obtained and the delamination damage mechanism of the composites is investigated by the microscopic observation of a fractured specimen. The results show that the micro-damage accumulation around the crack tip region has a great effect on the evolutionary process of delamination. AE characteristics and amplitude spectrum represent the damage and the physical mechanism originating from the hierarchical microstructure. Our finding provides a novel aud feasible strategy to simultaneously evaluate the dynamic response and micro-damage mechanism for fiber composites.

Intelligent Molding Proceeding of Composites and Intelligent Manufacturing Systems for Composite Materials

The technology of Intelligent cure operation is set forth according to developing tedency of smart material and structure. Intelligent-system-based tool was developed in order to operate the autoclave cure of a fiber reinforced thermosetting matrix composite laminate in an optimal manner.The objective function is comforts for minimizing the total cure time,uniforming the temperature distribution,controling exothermal and minimizing the process-induced residual stresses in the laminate.Data is analyzed on-line to determine the trends in real-time.The results from application of this overall strategy for the curing of composites are presented.

A STUDY OF THE POSTBUCKLING PATH OF CYLINDRICALLY CURVED PANELS OF LAMINATED COMPOSITE MATERIALS DURING LOADING AND UNLOADING

In this paper, Dynamic Relaxation Method is applied to study the postbuckling path of cylindrically curved panels of laminated composite materials during loading and unloading. The phenomenon that loading paths do not coincide with unloading paths has been found. Numerical results are given for cylindrically curved cross-ply panels subjected to uniform uniaxial compression under two types of boundary conditions. The influence of the number of layers, the panels curvature and the initial imperfection on the postbuckling paths is discussed.

Effect of Resin Composite Materials Containing Tourmaline Powders Modified with Lanthanum Element on Diesel Oil Combustion

The resin composite materials (RCM) were prepared by the method of doping resin with tourmaline powders modified with lanthanum element. It was characterized by scanning electron microscope (SEM), IR radiation determination, X-ray diffraction (XRD), and fourier transform infrared spectroscope (FTIR). The results showed that the RCM could radiate higher intensity of far infrared. The molecular movement was strengthened and the inter-molecular contacts were easily reduced when the diesel oil was dealt with the RCM. The effects of the RCM on the oil consumption and air pollutant emissions of oil-burning boiler were investigated. The oil-saving rate of the RBS·VH-1.5 boiler dealt with the RCM was 2.76%, and the reducing rates of CO and NO in the exhaust gas were 32.9% and 15.8%, respectively.

Effects of Far-Infrared Composite Materials Doped with Rare Earth on Physicochemical Properties of Diesel Fuel

The rare earth, far-infrared natural mineral and clay were compounded to prepare the far-infrared composite materials. The effects of the far-infrared composite materials on the physicochemical properties of diesel fuel were studied. It shows that the composite materials can radiate higher intensity of far infrared; and the surface tension, viscosity and flash point decrease when the diesel fuel is dealt with the composite materials containing rare earth elements; and then the available effect mechanisms of the composite materials on the properties of diesel fuel were investigated by testing the activity changes of arene.

Effects on Combustion of Gasoline of Rare Earth Composite Materials for Far Infrared Radiation

The rare earth composite materials (RECMS) for far infrared radiation were prepared using rare earth elements and natural mineral materials radiating far infrared. The effects of the granularity and rare earth additions on the far infrared radiation were investigated. The results show that the as-prepared composite materials with higher infrared radiance can enhance the combustion of gasoline, when the composite are about 4.24 μm in average granularity and comprise about 6% (mass fraction) of rare earth. Through bench test, the oil-saving rate of the engine dealt with the composite is 2.8%～3.7%, and the reducing rate of CO and HC in the exhaust gas is 20%～25% and 28%～30%, respectively.

New Technique for Making Composite Materials—Field Assisted Diffusion Bonding of Alumina to Aluminum

There are two ways to join ceramics to metals: brazing and bonding. However, brazing processes are time-comsuming and energy-comsuming and is limited by the low working temperature. Generally speaking, bonding, or specifically, Diffusion Bonding performs better than brazing. Besides diffusion bonding, a more specialized technique is Field Assisted Diffusion Bonding (FADB).

A DONNELL TYPE THEORY FOR FINITE DEFLECTION OF STIFFENED THIN CONICAL SHELLS COMPOSED OF COMPOSITE MATERIALS

A Donnell type theory is developed for finite deflection of closely stiffened truncated laminated composite conical shells under arbitrary loads by using the variational calculus and smeared-stiffener theory. The most general bending-stretching coupling and the effect of eccentricity of stiffeners are considered. The equilibrium equations, boundary conditions and the equation of compatibility are derived. The new equations of the mixed-type of stiffened laminated composite conical shells are obtained in terms of the transverse deflection and stress function. The simplified equations are also given for some commonly encountered cases.

RANDOM MICROSTRUCTURE FINITE ELEMENT METHOD FOR EFFECTIVE NONLINEAR PROPERTIES OF COMPOSITE MATERIALS

Some theoretical methods have been reported to deal with nonlinear problems of composite materials but the accuracy is not so good. In the meantime, a lot of linear problems are difficult to be managed by the theoretical methods. The present study aims to use the developed method, the random microstructure finite element method, to deal with these nonlinear problems. In this paper, the random microstructure finite element method is used to deal with all three kinds of nonlinear property problems of composite materials. The analyzed results suggest the influences of the nonlinear phenomena on the effective properties of composite materials are significant and the random microstructure finite element method is an effective tool to investigate the nonlinear problems.