Advanced Materials Research Vols. 150-151

Abstract: The stress-strain model of concrete prism after high temperature confined by CFRP is scarce, which gives great trouble to the study of mechanical properties of compressed concrete member after fire strengthened by CFRP. This paper presents the results of an experimental study on effects of temperature on characteristic parameters of CFRP-wrapped concrete prisms at elevated temperature. Experimental results indicate that strength and ductility of CFRP-confined concrete prism after high temperature have a large certain extent increase as the result of the action of CFRP. The results reveal that transitional stress, transitional strain, ultimate stress and ultimate strain are related to width of CFRP strip, the greatest temperature, corner radius and layers of CFRP. This has established reliable foundation for the accurate calculation of concrete structures strengthened by CFRP after high temperature or post fire.

Abstract: Ethylene-Octane copolymer (POE) and calcium carbonate (CaCO3) were used to improve the mechanical properties of HDPE/UHMWPE films and the effects of POE and CaCO3 content on the mechanical properties, melting curves and crystallization morphology of the blends were discussed. The results showed that adding 10wt% POE and 5wt% CaCO3 into the HDPE/UHMWPE blends simultaneously improved the toughness and stiffness of the film. The data from DSC revealed that POE retarded the growing of the crystal region while CaCO3 had the nucleation affect. The micrograph of the blends observed by polarized light microscope (PLM) confirms this deduction.

Abstract: The Fe3Al/Al2O3 composites were fabricated by pressureless sintering process. The Fe3Al intermetallics compounds powders were fabricated by mechanical alloying and heat treatment, then the Fe3Al powders and Al2O3 powders were mixed and the Fe3Al/Al2O3 composite powders were prepared, so the Fe3Al/Al2O3 composites were fabricated by sintering process at 1700oC for 2h. The phase composition and microstructure of Fe3Al intermetallics compounds powders produced by mechanical alloying and heat treatment were investigated. The phase composition, microstructure and mechanical properties of the Fe3Al/Al2O3 composites sintered bulks were investigated. The XRD patterns results showed that there existed Fe3Al phase and Al2O3 phase in the sintered composites. The Fe3Al/Al2O3 composites sintered bulks exhibited the homogenous and compact microstructure, the Fe3Al particles were homogenously distributed in the Al2O3 matrix, the mean particles size of Fe3Al intermetallics was about 3-5μm. The Fe3Al/Al2O3 composites exhibited more homogenous and compact microstructure with the increase of Fe3Al content in the Al2O3 matrix. The density and relative density of the Fe3Al/Al2O3 composites increased gradually with the increase of Fe3Al content. The fracture strength and fracture toughness of the Fe3Al/Al2O3 composites increased gradually with the increase of Fe3Al content. The elastic modulus and hardness (HRA) of the Fe3Al/Al2O3 composites decreased gradually with the increase of Fe3Al content.

Abstract: The cure kinetics of Derakane 411-350, a kind of vinyl ester resin, and its suspensions containing multi-walled carbon nanotubes( MWCNTs) were investigated via non-isothermal dynamic scanning calorimetry (DSC) measurements. The results showed that incorporation of MWCNTs into vinyl ester resin excessively reduces polymerization degree and crosslinking density of vinyl ester resin. For suppressing the negative effect caused by nanotubes, the higher temperature initiator combined with the initiator MEKP was used. Dynamic-mechanical Behavior testing was then carried out on the cured sample in order to relate the curing behavior of MWCNTs modified resin suspensions to mechanical response of their resulting nanocomposites. It was revealed that nanocomposites containing MWCNTs possessed larger storage modulus values as well as higher glass transition temperatures (Tg) as compared to those without MWCNTs after using mixed intiators system to improve the degree of cure.

Abstract: Nanocomposites based on epoxy which were reinforced by different nanoparticles were fabricated. Five types of nanoparticles (corresponding to multi-walled carbon nanotubes (MWNTs), nano-Al2O3, nano-TiO2 and nano-SiO2) were chosen and the weight content of the nanoparticles was 2wt.%. Impact, flexural and thermal-mechanical properties of the nanocomposites were investigated. Compared with neat epoxy, impact strength of systems which were reinforced by MWNTs and nano-TiO2 was increased by 60%. Concerned with the flexural properties, there was also an increase of about 10%~50% with the addition of the some nanoparticles such as MWNTs, nano-TiO2 and nano-SiO2. The heat resistance of the EP was not decreased by adding nanoparticles and the thermal properties of the systems were even improved with the addition of MWNTs.

Abstract: The TiO2 film loaded on fiberglass mesh was prepared by sol-gel method using butyl titanate as raw material, and the catalyst was characterized by scanning electron microscopy (SEM) and X-ray diffraction(XRD).The catalyst surface of loaded TiO2 can obviously observe solid particles and agglomeration to some extent, the crystalline phase was anatase, and no rutile was observed, the average particle diameter of TiO2 was 40nm,Under the ultraviolet light UV-C irradiation, the photocatalytic oxidation experiments of humic acid solution was conducted. The results showed that the prepared photocatalyst has a high photocatalytic activity, the UV254 degradation rate of humic acid solution in 60min reached 96.9%, but the degradation rate of TOC is only 57.3%, indicating that the organisms in humic acid can not be completely mineralized in photocatalytic oxidation process.

Abstract: Laminated Veneer Lumber (LVL) panels made from pine (Pinus sylvestris L. Var. mongolica Litven.) veneers were tested for mechanical properties and prediction models in this study. Three different nondestructive testing (NDT) methods and the static bending test were conducted on the LVL. The NDT methods included the longitudinal vibration method, longitudinal transmission method and flexural vibration method. The effects of veneer thickness on the dynamic Young’s modulus and the modulus of elasticity (MOE) of pine LVL with vertical load were investigated. There were four variety thickness veneers including 2.2 mm, 2.6 mm, 3.0 mm and 3.4 mm. The results showed that the dynamic Young’s modulus and MOE of LVL diminished with the increase of veneer thickness, there was a strong linearity correlation between each dynamic Young’s modulus and the static MOE, and the prediction models of mechanical properties can be used to predict MOE of pine LVL.

Abstract: The Fe-based composite coating reinforced by in situ synthesized multiphase ceramic particles has been successfully prepared by laser cladding preplaced powder on 42CrMo steel. The experimental results of X-ray diffraction and scanning electron micrograph indicate the coating is consisted by γ-Fe phase and Fe-Cr fine phase which possesses the better oxidation resistance and corrosion resistance. In-situ synthesized V(C,N), Cr2B3 and Cr3C2 particulates which are uniformly distributed in the composite coatings. The wear test showed that these reinforcement particulates improved significantly wear resistance of the coatings. The wear mass loss of the coating is about one tenth of the 42CrMo substrate. Laser cladding layers have better oxidation resistance. The oxide scale of the coatings is one eighth of the substrate through 750 constant temperature for 120h oxidation.

Abstract: Small diameter bamboo and bamboo processing residues were cut into particles; bamboo particles and bamboo mat were constructed into a composite mat; the composite mat was hot-pressed to form a composite board. A study was made of the hot-pressing process for bamboo mat bamboo particle composite boards, taking its hot-pressing time, hot-pressing temperature and glue consumption as the process variables. An analysis of the variance and regression of the test results shows that, among the three variables, glue consumption has the largest effect on every quality index of the product, hot-pressing time has less, and hot-pressing temperature has the least. Based on this, the optimal variables have been determined.Hot-pressing time is 70s/mm, hot-pressing temperature is 170 , and glue consumption is 12%. Prediction and verification of the variables show that these variables are reasonable and helpful in bettering product quality. Advantage of the presented technology was to make full use of character of bamboo mat and bamboo particle, and to raise the rate of bamboo utilization.

Abstract: Biodegradable composites of polylactic acid reinforced with wood fiber were fabricated by using twin screw extruder followed by the injection molding machine. The effects of different pretreatments of wood on mechanical properties of the biodegradable composite were discussed. The nature of composites were also examined through scanning electron microscope and Infrared Spectrum Analysis, the results reveal that both acid and stearic acid could be used as effective surface modifier for wood fiber/polylactic acid system, the composite system by adding Benzoic acid, the tensile strength has improved greatly, and about stearic acid composite system, the impact strength has improved significantly; After alkali treatment, coupling agent treatment and combination of alkali treatment and coupling agent treatment, and the use of alkali treatment and the coupling agent treatment is the best, follow by alkali treatment.