Advanced Materials Research Vols. 194-196

Abstract: Carbon fiber reinforced Ultra High Molecular Weight Polyethylene (CF/UHMWPE) composites have been filled with acid treated carbon nanotube to enhance the tribological properties. According to the modification, the friction and wear properties of composites have been greatly improved. XPS and SEM are used to examine the microscopic properties of resultant composites. The enhanced tribological properties are attributed to the acid treated CNT interlock, which improves the wetting between carbon fibers and resins.

Abstract: The Fe₃Al/Al₂O₃ composites were fabricated by plasma active 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 plasma active sintering process at 1200°C for 5min under the pressure of 30MPa. The phase composition and microstructure of the Fe₃Al intermetallics compounds powders produced by mechanical alloying and heat treatment were investigated. The phase composition, microstructure and mechanical property 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 2-3μm and mean particles sizes of Al₂O₃ was about 2-3μm. 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 Fe₃Al/Al₂O₃ composites decreased gradually with the increase of Fe₃Al content.

Abstract: Polypropylene (PP) fiber reinforced concrete is an important composite. In order to improve the mechanical properties of PP fiber reinforced concrete, polyacrylamide (PAM) was grafted onto the PP surface by the UV irradiation to enhance the hydrophilic property of PP in this study. IR spectra showed the existence of carboxylic acid functional groups on the treated PP surface. AFM images depicted that the treated PP surface had the lower height fluctuation, roughness, and had the acicular appearance. Contact angles of the treated PP were reduced in comparison with that of the original PP. All of these experimental results gave the evidences that PAM had been successfully grafted onto the treated PP surface. Furthermore, OM images depicted that the treated PP adhered to cement hydrate products (C-S-H) more tightly than that of the original PP did. We therefore expect that PP grafted with PAM can enhance mechanical properties of PP fiber reinforced concrete.

Abstract: Delamination is one of the important damage modes in the fiber-reinforced composite laminates. The interlaminar fracture toughness is the key parameter in delamination failure analysis of composites. The stress analysis by a finite element modeling has shown that the shear stress is very large near the ply splicing area. So the delamination failure is mainly dependent on the mode II fracture toughness. A new way of loading in tensile testing is proposed for the measurement of mode II fracture toughness. Specific specimen with splicing plies has been designed and used for the experiment. Testing study on the carbon-fiber-reinforced laminate with ply splicing was performed. Steady crack propagation has been seen by the tensile testing of the specimen. Mode II fracture toughness GIIC of the laminate has been determined by the experiment data analysis. The experiment and numerical analysis shows that the tensile testing for the measurement of mode II interlaminar fracture toughness is feasible.

Abstract: A two-layer structure composite based on B₄C/Al-B₄C/TiB₂ was prepared using hot pressing and infiltration aluminum in vacuum. The results showed that the B₄C porous layer in the two-layer preform looked like a three-dimensional network of interconnected capillaries which could promote the infiltration of liquid aluminum. In the B₄C/TiB₂ layer the TiB₂ dispersed homogenously in B₄C matrix. After infiltrating process the two-layer B₄C/Al-B₄C/TiB₂ composite with good interfacial bonding was obtained.

Abstract: Banana fiber/tapioca starch (BFRTPS) composites modified by magnesium hydroxide (Mg(OH)₂) were prepared with glycerin as the plasticizer, banana fiber as reinforcement and thermoplastic tapioca starch as matrix. Rheological properties testing showed that Mg(OH)₂ take a strong effect to the preparation processing and made it hard to mix while the content increasing. Mechanical properties testing revealed that at the range of the Mg(OH)₂ content from 5 to 20phr, the tensile strength of the composites increased from 12.8MPa to 24.8MPa at 15phr Mg(OH)₂ content, but its elastic modulus was increased with the increasing of Mg(OH)₂, reached the maximum of 3100MPa at 20phr Mg(OH)₂ content. Obviously, Mg(OH)₂ has an enforced effect to the composites. Combustion performances of the composites was improved by Mg(OH)₂, the limited oxygen index(LOI) of the composites reached to 31% while the content of Mg(OH)₂ was 20phr, and then the result of flammability testing achieved UL94HF-1 and UL94 V-0 level.

Abstract: This study proposed non-failure or non-disabled probability of structure suffering random dynamic load within given time. A wavelet method based on its conception was proposed for seismic dynamic reliability analysis of MDOF system：From the Duhamel integral of the dynamic structural response, the structure stochastic response was expressed as earthquake ground motion’s wavelet transform. The ground motion and structure responses were modeled as non-stationary random process using odd exponent wavelets. The first-passage failure criterion and maximum probability were employed to estimate the structural dynamic reliability. The primary advantage of the proposed method is that it does not need to calculate spectral moments from the power density function integral, which are usually difficult to obtain the analytical expressions.

Abstract: This paper presents the results of synthesizing porous Si₃N₄-glass composite with Y₂O₃ as additives by combustion synthesis. The effect of glass content on the final morphology was investigated in detail. The results reveal that the final morphology of products is depended on the glass content. With the increasing glass content, the porosity of the composite is decreasing and the highest strength is obtained when the glass content is 2wt%.

Abstract: Microstructure and mechanical property of a hypoeutectic Al-Mg₂Si composite processed by equal channel angular pressing up to eight passes in a combined route 2A+4B_A+2A were investigated. The results show that the initial developed eutectic Mg₂Si was significantly refined into submicrometer-scale particles and distributed homogeneously in the Al matrix, which together with the refinement of Al matrix leads to a much higher ductility with the elongation to failure up to 24% and a significantly enhanced ultimate tensile strength of 284MPa in the processed composite, increased by 2300% and 70%, respectively, compared to those in its as-cast counterpart.

Abstract: ZrO₂-Al₂TiO₅ composite materials with high bending strength and good thermal shock resistance expansion were prepared using partially stabilized zirconia (Y-PSZ) powders coated with Al₂TiO₅ by co-precipitation method. The effects of Al₂TiO₅ content on the sintering properties, phase composition, microstructure and thermal shock resistance of the zirconia ceramic were investigated．The results show that the apparent porosity of the samples decreased and their bending strength increased with the content of aluminum titanate increasing from 0 to 8 wt%. The samples with 5 and 8 wt% aluminum titanate addtion have excellent thermal shock resistance. The results showed that the addtion of aluminum titanate could enhance the mechanical strength and improve the thermal shock resistance of zirconia ceramic. The XRD and SEM analysis results indicated that the propriety improvement is relative with the change of the microstructure and the increase of tetragonal ZrO₂ phase in the composites.