Advanced Materials Research Vols. 168-170

Abstract: A large-scale laboratory apparatus has been built to study the pullout behavior of mortar grouted glass fiber reinforced polymer (GFRP) soil nails. The axial strain along the nail length and the displacement of the nail head under different pullout loads are measured, and the ultimate pullout load under the overburden pressure is obtained. Then, the influence of the overburden pressure on the ultimate value of the interface friction force is investigated. The experimental results illustrate that the pullout behavior of mortar grouted GFRP soil nails is similar to that of mortar grouted steel soil nails, and the relation between the displacement and the pullout load can be described with the hyperbolic function. In addition, the dilatancy effect of the soil near the nail during pull out should be taken into account in estimating the pullout resistance of soil nails in dense fills.

Abstract: The study on contraction of high performance concrete affected by slag, ash, silica fume, concrete shrinkage reducing admixture and water reducing admixture indicates that early contraction distortion of high-performance concrete is more complex that of ordinary concrete. A practical model for calculating stressis given.Compared to ordinary model of contraction, the proposed model in the paper is more suitable for the contraction distortion calculation of high performance concrete.

Abstract: A new method is proposed to prepare carbon fiber reinforced concrete (CFRC) and carbon fiber (CF)/carbon black (CB) reinforced concrete in this paper. First, CF is dispersed in 0.4% carboxymethylcellulose sodium (CMC) water solution. Then, resolvable carbon fiber surfacing mat (RCFCM) is manufactured and cut into small patches. Finally, these patches are mixed with cement, sand, gravel, CB and water. During mixing, RCFCM patches are broken up once they meet with water. So, CF is dispersed into concrete. Results show that this method is feasible. CF/CB reinforced concrete possesses low resistivity (<100 Ω•cm), high compressive strength (≥35 MPa) and low contents of CF (0.3 Vol.%) and CB (0.6 Vol.%), so it can be used as a kind of conductive concrete for melting snow and deicing applications on highways. Both the mixing time and the curing period can affect the electrical and mechanical properties of CF/CB reinforced concrete.

Abstract: With photolithography process and screen printing technique, the compound cold cathode electrode was developed on the cathode glass plate for improving the field emission ability and emission uniformity of CNT cathode. The compound cold cathode electrode mainly consisted of the indium tin oxide (ITO) blocks which was the divided ITO thin film, the bar silver stripes fabricated by the solidified silver slurry and the cathode insulation layer with good insulation performance. Carbon nanotubes were prepared to form the field emitters, and the diode type field emission display (FED) was fabricated. The manufacture process was also presented in detail. The vacuum sealed FED exhibited better field emission characteristic, low operating voltage and high display brightness.

Abstract: Using insulation slurry as material, the combined type insulation wall was developed with the high-effective screen-printing process. Two parts were mainly included for the combined type insulation wall, which was the lower insulation wall prepared on the cathode panel and the upper insulation wall fabricated on the anode panel, respectively. The fabricated combined type insulation wall possessed better insulation performance, and was used to separate the cathode and anode panel. Using carbon nanotube as cathode material, the field emission display with the combined type insulation wall was fabricated, and the detailed manufacture process was also presented. The sealed field emission display showed high luminance brightness, stable emission current and good field emission properties.

Abstract: Near-field seismic motion characteristics are analyzed in accordance with records of the 2008 Ms8.0 Wenchuan Earthquake measured at Wolong Station, upon which the determination of seismic load is introduced. Dynamic response features, such as acceleration, displacement and stress, of high steep rock slopes on the banks of Zipingpu Reservoir at a variety of locations resulting from horizontal seismic force are analyzed with a numerical analysis routine. The dynamic amplification factor on the slope top is determined, leading to a characterization of the mode of failure of the high steep slope. Analyses show that the dynamic amplification factor at the top of the slopes is about 1.34; however, dynamic response deformation features and stress state at different positions on the slope vary. Earthquake damage of the high steep rock slopes consists mainly of partial avalanche of the rock mass at the top of the slopes by joint cutting. Field investigations after the earthquake have partially confirmed the numerical analysis results presented in this paper.

Abstract: In this article soil is treated as non-uniform material including two parts : the matrix particles and the reinforcement particles. Through soil shear strain energy and micro-crack assumptions, we establish a multiphase constitutive model connecting macro and micro scale based on classical continuum models, which includes the strain gradient, internal length scales and particle size. This model have been verified reasonable by artificial soil experiment.

Abstract: Owing to its outstanding characteristics in good affinity to heterogeneous materials, corrosion resistance and on-the-spot processing capability, epoxy has been widely used as adhesives in retrofitting structures with carbon fibre reinforced polymer (CFRP). In this study, different weight fractions of multi-walled carbon nanotubes (MWCNTs) will be dispersed into epoxy to produce toughened adhesives that can improve the CFRP/structure bonding performance. The preliminary results indicate that adding 2% MWCNTs to Araldite-420 increase its ultimate strength by 17% and its elastic modulus by 14%. Ultrasonic mixing may increase Sikadur-30’s elastic modulus but reduce its strength and ductility regardless of the MWCNTs concentration. The mechanism of MWCNTs infusion effects on the mechanical properties of epoxy is also examined using SEM.

Abstract: Laminated composites are the effective ways to toughen Al2O3 ceramics at present. The destruction process analysis of laminated ceramic composite is studied in this paper taking the Al2O3/ZrO2 ceramic composite as the example through the APDL programming. The micro model is established in ANSYS. And the failure stresses of each ply of the ceramic can be calculated by micromechanics method. Then the calculated failure stresses are compared to the simulated failure stresses. The micro model can visualize the destruction process of laminated ceramic composite. The failure criteria of composite material can be self-defining in ANSYS by using APDL. Some ideas of ANSYS application on composite material are given in this paper.

Abstract: Novel shaped phase change plate was made of wheat straw impregnated with Na₂SO₄ solution and water glass as cementing agent. The plate was subsequently inserted into the concrete bricks with rectangular holes, assembled as phase change bricks. The latent heat of phase change of the plate was measured by DSC, the microstructure of the plate was observed by SEM, and the performance of the plate was also measured. In addition, the heat insulating property of the brick was investigated. The results are as follows. The wheat straws can encapsulate 1.86 times Na₂SO₄•10H₂O in mass,and the phase change heat of the plate is 113 J/g. The microstructure shows that the straws and hardened water glass play an encapsulating action for Na₂SO₄•10H₂O. The weight loss of the plate was 1.8% after 30 times of phase change cycles. For the concrete bricks (size: 240×240×115 mm) inserted with phase change plates, when the heated surface temperature was 80 oC for 5 h or 8 h , the cold surface temperature increased by only 1.8 oC and 4.4 oC respetively ,that is, the temperature difference between the cold with hot surface was 63.7 oC and 61.1 oC. This study reflects that if the brick is used as walling material, interior temperature does not fluctuate, even in extreme heat summer. It has dramatically saving energy and the effect of improving inhabited environment.