Xiaoming Zhao

The research of EM wave absorbing properties of ferrite/silicon carbide/graphite three-layer composite coating knitted fabrics

The polyester knitted fabric was used as a basilicon carbide structure material. A three-layer composite coating finishing was applied to the structure material using ferrite, silicon carbide, and graphite absorbing materials. The single factor test method was used in this series of research. The impact on dielectric constant and loss tangent of absorbtion of each agent and the coating thickness of each layer were studied. From these results, the three-layer composite coating materials that had excellent absorbing properties were selected and prepared. The results showed that when the ferrite (60 wt%) was used as a bottom layer, the silicon carbide (36 wt%) was used as a middle layer and the graphite (24 wt%) was used as a surface layer with the respective thickness of 0.5, 0.3, and 0.3 mm, an excellent microwave absorbing property was noted for the three-layer composite coating material. In order to meet the requirements for the engineering field, physilicon carbideal and mechanical properties of the microwave absorbing materials were also characterized.

Preparation of polypyrrole coated cotton conductive fabrics

Abstract Polypyrrole-coated cotton conductive fabrics were prepared by in situ polymerization. The influences of pyrrole dosage, mole ratio of pyrrole to iron (III) chloride, reaction temperature and reaction time on the conductivity of the polypyrrole-coated cotton conductive fabrics were analyzed. The best method for preparing the polypyrrole-coated cotton conductive fabrics was determined. The structures of the conductive cotton fabrics were characterized with Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that when mo1e ratio of pyrrole to iron (III) chloride was 2:1, reaction at room temperature for 1 h with a bath ratio of 1:40, the conductivity of the prepared fabric was the best with a surface resistance of 0.15 kΩ/cm. The chemical structure and the surface morphological structures of the conductive cotton fabrics were different from that of the untreated cotton fabrics. By in situ polymerization, the fiber surfaces appeared homogeneously coated with a film of polypyrrole. Importantly, the process of pyrrole polymerization is very simple. This study offers a new simple way for preparing the polypyrrole-coated cotton conductive fabrics effectively.

Analysis of flexural strength of preoxidized fiber-reinforced composites made by a nonwoven process and hot-pressing

Abstract Preoxidized fiber was used here as a reinforcement for the first time. Polypropylene fiber was used as resin matrix, and the preform with the two types of fiber was prepared by a nonwoven process. Then, hot-pressing was applied to make a treatment for the preform, and the thermoplastic composites reinforced with preoxidized fiber were prepared. The effects of the hot-pressing temperature, hot-pressing pressure, weight percentage of preoxidized fiber, and nonwoven process on bending failure strength along the machine direction (MD) and transverse direction (CD) were studied under a three-point bending load. It was concluded that the flexural strength of the composites along MD and CD decreases with increasing hot-pressing temperature and hot-pressing pressure, while an initial increase and then decrease was observed with the increase in the weight percentage of preoxidized fiber. However in both directions, flexural strength of the composites is influenced significantly by the nonwoven process. Finally, the bending failure mode of the composites generated micro-flaws, which can be observed on the center surface of the composites. The micro-flaws extend to the ends along the thickness direction of the composites, and plastic bending failure is observed due to partial delamination.

Study of graphite/silicon carbide coating of plain woven fabric for electrical megawatt absorbing properties

Abstract In this paper, plain woven fabric was selected as the base fabric. Graphite and silicon carbide were the surface layer and underlying layer absorbents, respectively. The influence of the content of the graphite and silicon carbide absorbent and coating thickness on the real part and the imaginary part of the dielectric constant, and the loss tangent are discussed. Through the optimization of electromagnetic parameters, graphite/silicon carbide double-coated polyester woven fabric absorbing materials with the best wave absorption performance were prepared.

Investigation of automated geometry modeling process of woven fabrics based on the yarn structures

Fabric structure has a significant effect on the thermal protective performance of fabrics. Before studying the thermal performance of textiles by numerical methods, it is essential to create geometric models of textile structures. Common fabrics, such as plain weave, 2/1 twill, 3/3 twill, 5/3 satin, and double layer fabric, were modeled using TexGen software. To obtain the input data for geometry simulation of fabrics, geometric measurements were studied. Methods of modeling fabric geometries according to their yarn path function and cross-sectional shapes were introduced. The appearances of the geometric models were very close to the structures of the real fabrics when compared to their light microscopic images. The fabric models were well used to simulate the heat transfer properties of glass fiber fabrics.

Simulation of the effects of structural parameters of glass fiber fabric on the thermal insulation property

The impact of different structural parameters on the thermal insulation of glass fiber fabrics, by using numerical simulation, was investigated. The structural parameters investigated were the weave structure, warp density and yarn fineness. A series of structure models were calculated under the same boundary and initial conditions, which combine thermal radiation, conduction and convection. The simulation results have been validated by experiments. The experimental results and the predictions from numerical simulations were in good agreement. The results show that thermal insulation for the samples is in the order plain < 2/1 twill < 2/2 twill < 2/3 twill < 3/3 twill fabric, when using constant structure density and yarn fineness. Increasing the warp density, from 110 to 160 ends/10 cm, leads to a significant decrease in heat transfer performance. When the warp density increases to more than 160 ends/10 cm, the thermal insulation property shows a decreasing trend with an increase in warp density. Furthermore, thermal insulation performance of the samples dramatically increases as yarn fineness goes from 129 to 280 tex, and then decreases for yarn fineness greater than 280 tex. This study will provide the theoretical basis for the thermal design and application of fibrous materials.

An investigation into the anti-icing properties of fabrics used for the outer layer of firefighter clothing

The anti-icing properties of fabrics can be considered as involving two parts, the super-hydrophobic property and the ease of ice removal property. In this study, a super-hydrophobic surface was built on to the outer layer of firefighter clothing using nano-silica, C13H13F17O3Si, C19H42O3Si and PU-2540 using a coating method. This coating stops water drops from staying on the fabric surface easily. At the same time, an ultra-smooth surface was built on to the super-hydrophobic surface already created on the fabric using perfluoropolyethers (PFPE) oil by a dipping method, which adds an ice removal function to the fabrics. The anti-icing properties of the samples prepared in the research described in this paper have been investigated using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), ease of ice removal property tests and static water contact angle analysis. At the same time, the thermal protective performance (TPP) of the samples, before and after super-hydrophobic treatment, was studied by a TPP tester. Results show that the super-hydrophobic coating with an ultra-smooth surface can significantly increase the anti-icing properties of the fabrics used for the outer layer of firefighter clothing. C13H13F17O3Si and C19H42O3Si can improve the hydrophobic properties of the coating. The anti-icing coating in this paper can increase the TPP of the fabrics.

A study of the thermal protective performance of the outer fabric material for fire proximity suits

Abstract The thermal performances such as thermal conductivity, radiant heat reflection, X-ray diffraction spectra, thermogravimetric data, and thermal protection performance (TPP) of three types of outer fabric materials for fire protection suits were compared. Three types of fire proximity suits’ outermost fabrics are high silica glass fiber fabrics (A1), high silica glass fiber fabrics (B1), and continuous basalt fiber fabrics (XW). The explanation and analysis of the reasons for the difference in thermal protective performance among the three types of materials were carried out, one by one, from the perspective of the microscopic molecular architecture of the yarn and macroscopic fabric structure. The sizes of the influence for related indicators of all types of thermal performances on the TPP value of the fabric were calculated. According to the analysis and calculation results, it can be concluded that the thermal conductivity of the fabric is the decisive factor influencing the size of the TPP value for the fabric. Therefore, reducing the thermal conductivity of the fabrics and improving the thermal insulation efficiency of the fabric is the best way to improve their thermal protective performance.

The influence of the type and concentration of oxidants on the dielectric constant of the polypyrrole-coated plain woven cotton fabric

Abstract The influences of the type and concentration of the oxidant on the real and imaginary parts of the dielectric constant, the loss tangent, and the surface resistance of the polypyrrole-coated plain woven cotton fabric were investigated. Subsequently, exterior morphologies were analyzed. The results showed that the type and concentration of the oxidant had a major influence on the real and imaginary parts of the dielectric constant, the loss tangent, and the surface resistance of the polypyrrole-coated plain woven cotton fabric. The composites showed good performance in terms of the dielectric properties, and conductivity. The ability of coupling is relatively good in the group whose molar ratio of the dosage of oxidant and pyrrole is 2:3. The dosage of oxidant has a major influence on the resistance of the polypyrrole-coated plain woven cotton fabric. When the initial molar ratio of the iron (III) chloride and pyrrole is 3:2, the value of the surface resistance is at its smallest, and the electrical conductivity is at its best.

A study of the mechanical properties of pre-oxidized fiber felt/epoxy resin composite material

Abstract In this article, the pre-oxidized fiber felt composite material was firstly prepared by a mold press process, and the pre-oxidized fiber and resin were used as the reinforcing material and substrate of composite material, respectively. The pretreatment method of the pre-oxidized fiber felt and the impact of the amount of curing agent and the curing pressure on the mechanical properties of the composite material were studied, and the tensile and flexural properties were assessed to optimize the preparation process of composite material. Results show that when the curing agent accounts for 60% of the epoxy resin and the curing pressure is 3 MPa, the best tensile and flexural properties of the prepared composite material are achieved. The mechanical properties for the pretreated composite sheet prepared from pre-oxidized fiber were superior to those for the untreated sheet.