YAO Xue-li, MA Xiao-yan, QU Xiao-hong, QIN Yu-xia, CHEN Fang. Preparing Process on Toughening and Strengthening Cyanate Ester with Nano-SiO2[J]. Journal of Materials Engineering, 2006, 0(5): 3-6,11.
SiO2/cyanate ester(CE) nano-composites were prepared in situ polymerization, and three different methods of dispersing nano-SiO2 (attrition treatment,coupling agent surface treatment,high-speed homogeneous shearing) were investigated. Nano-particle dispersion,mechanical and thermal properties of nano-composites under three dispersing methods were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM) and thermogravimetric analysis(TGA). The characterization results showed that attrition treatment produced nano-composites with more excellent nano-particle dispersion than high-speed homogeneous shearing, however, coupling agent surface treatment couldn’t disperse SiO2 in nanometer size range. High-speed homogeneous shearing better improved mechanical and thermal properties of composites, and when nano-SiO2 was 1phr (per hundred resin),the impact strength and the flexural strength of composites were respectively 35.0% and 12.1% higher than pure CE; and when the mass loss of composites was 5%, its degradation temperature improved 23.8℃ compared with pure CE. Coupling agent surface treatment decreased the flexural strength and degradation temperature of composites.
ZHOU Tong-yue, YU Yun-hua, CHEN Wei-ming, YANG Xiao-ping, GU Xue-lin, CHANG De-you. Electrochemical Corrosion Behavior of Carbon Fiber/Vinyl Ester Resin Composites Used for Sucker Rods[J]. Journal of Materials Engineering, 2006, 0(5): 7-11.
The electrochemical corrosion behavior of carbon fiber/vinyl ester resin composite (CF/VE), which was used for sucker rods in the oil field, was studied under the simulated service conditions in the oil field (3%(mass fraction) NaCl aqueous solution immersion at 65℃). Galvanic corrosion experiment between the CF/VE composite and the alloy used as joints linking the composite sucker rods and metal suckers was performed. Meanwhile, the effect of galvanic corrosion on the absorption behavior and the static and dynamic mechanical properties of the CF/VE composite was investigated. The results show that in a polarization system, there will be a cathode reaction of oxygen absorption on the surface of the composite and an anode reaction which is mainly depended on the concentration of the hydroxyl (OH-). A slight acceleration of the absorption behavior of the CF/VE composite is caused by the galvanic corrosion. In addition, the galvanic corrosion results in more decrease in the interlaminar shear strength (ILSS) and flexural strength of the CF/VE composite because of the occurrence of hydroxyl at the interface of the CF/VE composite.
ZHAO Hai-jun, LIU Lei, TANG Yi-ping, ZHU Jian-hua, HU Wen-bin. Investigation on Cu-graphite Composites Prepared by Electroforming[J]. Journal of Materials Engineering, 2006, 0(5): 12-15.
Cu-graphite composites were prepared by electroforming technology in an acidic copper sulfate solution. The processing factors, such as surfactant, particle concentration, current density, agitation rate, had different effect on the volume fraction of graphite particles in the composites. Non-ionic surfactant improved the codeposition of graphite particles with copper matrix. With increasing graphite content in Cu-graphite composites, microhardness and friction coefficient decreased. However, wear mass loss decreased at the beginning, and then increased. During friction process adhesive wear occurred for pure copper, but delaminating wear occurred for Cu-graphite composites.
YANG Guo, PAN Qin-yan, PAN Wan-jiang, FU Shao-yun. Influence of Flexible Amine Modifier on Mechanical Properties of Epoxy Resins[J]. Journal of Materials Engineering, 2006, 0(5): 16-20,24.
Epoxy resin structural adhesives modified by a flexible amine (D-230) were prepared by casting molding method. Dependence of the mechanical properties of epoxy resins on the flexible amine content was studied. The impact fracture toughness was discussed in terms of fracture surface fractography. The results showed that the fracture elongation at break at RT and the impact toughness at both RT and 77K increased with the increasing D-230 content, which demonstrated that the toughness of epoxy resin could be improved effectively by the addition of D-230. When the D-230 content was 21%(mass fraction), the epoxy resin at RT exhibited the highest tensile strength and Young’s modulus, 85.44 MPa and 3.22GPa, respectively; afterwards, both the tensile strength and Young’s modulus decreased with the increase of D-230 content. SEM analysis of tensile fracture surfaces showed that the fractography tended to be irregular with the addition of flexible amine, indicating that the crack-resisting ability was improved. This result was consistent with the observation of higher fracture elongation and higher impact toughness. Thermal analysis of specimens showed that the glass transition temperature (Tg) decreased with increasing the D-230 content.
LIU Hao, LI Ke-zhi, LI He-jun, LU Jin-hua, ZHAI Yan-qiang. Microstructure and Mechanical Properties of Mesophase Pitch-based C/C Composites[J]. Journal of Materials Engineering, 2006, 0(5): 21-24.
With 3K PAN-based carbon fibers as reinforcing materials and with mesophase pitch as matrix precursor, mesophase pitch-based 2D carbon-carbon composites were obtained by pressure impregnation carbonization technology under different carbonization pressure. The morphology, flexural property and fractured surface were analyzed. The result shows that the morphology of matrix carbon changes with different carbonization pressure. The morphology shows small domains under low carbonization pressure, and domains under carbonization pressure respectively. The flexural strength and density of C/C composites increase with increasing carbonization pressure, and the flexural strength is up to 278MPa. The fractured characters of C/C are related to density and inferface bonding strength. The fractured surfaces are made of fracture and pulling out of fiber when the density is high and the bonding is moderate,materials have toughness character.
BAI Tong-qing, TONG Lin-song, LI Dong-sheng. Effects of MoS2 on Properties of Copper-based Cermet Friction Materials[J]. Journal of Materials Engineering, 2006, 0(5): 25-27,31.
The effect of MoS2 content on the friction and wear properties of copper-based cermet material was investigated. The result showed that MoS2 was decomposed S and Mo during sintered; the most of the S were combined with Fe into FeS, which acted as friction material lubricant. With increasing MoS2 content, the wear resistance and stability coefficient were increased. However, the hardness and friction coefficient were decreased.
GONG Jun-jie, WANG Xin-wei. Effect of Trigger Geometry on Energy Absorption of Composite Waved-beams[J]. Journal of Materials Engineering, 2006, 0(5): 28-31.
The trigger geometry is a key technology to the ability of energy absorption of composite structures. Reasonable design of triggering mechanism can make composite structures destroyed steadily and gradually thus lead to more energy absorbed. The FEM models of three sets of waved-beams with different sizes were set up with the explicit finite element code MSC/DYTRAN. Based on the good correlation of experimental results and numerical data of waved-beams, the effect of different trigger geometries on the peak load and energy absorption property was analyzed. The energy absorption capability of the waved-beams with different trigger geometry was further compared when the waved beams impacted the rigid ground at a velocity of 6.5m/s.
Michael Cichon, Helen Wei Li, Alex Wong, Stan Lehmann, Raymond Wong. Henkel Technologies and Products for China Aerospace[J]. Journal of Materials Engineering, 2006, 0(5): 32-36.
Epoxy structural adhesives and composites have been in use for many years for the construction of aerospace vehicles. Henkel provides many epoxy products. Many other resin systems have been evaluated and several, such as imide, phenolic and cyanate ester, have also achieved significant use. Henkel’s newly developed “Epsilon” chemistry demonstrates unique features that benefit application in aerospace structure that use adhesives and composites.
Leonhard Maier, HU Pei, Herman Seibert. PMI Foam Cored Sandwich Components Produced by Means of Different Manufacturing Methods[J]. Journal of Materials Engineering, 2006, 0(5): 37-40,45.
The paper introduced the structural applications with PMI (Polymethacrylimide) foams in sandwich components for rotor craft, launching vehicle and civil aircraft and discuss some typically used manufacturing methods, such as e.g. in-mould pressing, autoclave curing and resin infusion. The advantages of foam-cored sandwich design versus honeycomb-cored design will be discussed, focussing on manufacturing costs.
CHENG Qun-feng, XU Ya-hong, YI Xiao-su. Toughening of BMI Based Graphite Laminates by Ex-situ Concept[J]. Journal of Materials Engineering, 2006, 0(5): 41-45.
High-performance bismaleimdes (BMI) matrix composites reinforced by graphite fibers were prepared and toughened with a thermoplastic component (PAEK) by using the Ex-situ concept. Experimental matrix was designed for overall toughening of the base resin, periodically interleaving thermoplastic films into each plies (Ex-situ concept) and for varying the film compositions. The highest impact damage resistance characterized by compression after impact (CAI) was obtained for the laminates toughened on the Ex-situ concept, especially, when two-component cast films of a special ration of PAEK/BMI 60:40 were interleaved though the thermoplastic concentration for the overall toughening, interleaving the pure thermoplastic films and the two-component films was comparable. There were two peaks found in the DSC trace of the laminates toughened implying a phase separation process occurred. The glass transition temperature of the laminates toughened was slightly reduced due to the low-temperature PAEK. Morphological study revealed a typical granular structure just in the interplay region as a result of spinodal decomposition and coarsening process. This was in agreement of the result of DSC investigation.
YANG Bin, XIONG Tao, XIONG Jie. Statistical Tensile Strength for High Strain Rate of Aramid and UHMWPE Fibers[J]. Journal of Materials Engineering, 2006, 0(5): 46-50.
Dynamic tensile impact properties of aramid (Technora) and UHMWPE (DC851) fiber bundles were studied at two high strain rates by means of reflecting type Split Hopkinson Bar, and stress-strain curves of fiber yarns at different strain rates were obtained. Experimental results show that the initial elastic modulus, failure strength and unstable strain of aramid fiber yarns are strain rate insensitive, whereas the initial elastic modulus and unstable strain of UHMWPE fiber yarns are strain rate sensitive. A fiber-bundle statistical constitutive equation was used to describe the tensile behavior of aramid and UHMWPE fiber bundles at high strain rates. The good consistency between the simulated results and experimental data indicates that the modified double Weibull function can represent the tensile strength distribution of aramid and UHMWPE fibers and the method of extracting Weibull parameters from fiber bundles stress-strain data is valid.
LI J Y, DAI H, LI Q, ZHONG X H, CAO X Q. Improvement of Fracture Toughness Lanthanum Zirconate[J]. Journal of Materials Engineering, 2006, 0(5): 51-56,62.
La2Zr2O7(LZ) is a promising thermal barrier coating material for the high temperature applications. The fracture toughness and microhardness of nanocrystalline LZ (n-LZ), microcrystalline LZ (m-LZ) and LZ-5mol%8YSZ (LZ-5-8YSZ) composite (8YSZ for zirconia stabilized by 8 mol% ytrria) were studied. The n-LZ had a thermal expansion coefficient of (9.6±0.4)×10-6K-1(200～1000℃) and fracture toughness of (1.98±0.07) MPa·m1/2 which are obviously higher than those of the m-LZ ((9.1±0.4)×10-6 K-1 and (1.40±0.23) MPa·m1/2, respectively), indicating that nanofication was an efficient way to increase the toughness and thermal expansion coefficient of LZ. The composite LZ-5-8YSZ had a higher fracture toughness ((1.88±0.30) MPa·m1/2) than LZ, which was close to that of 8YSZ densified by superhigh pressure (SHP).
ZHANG Ming, AN Xue-feng, TANG Bang-ming, YI Xiao-su. Study on Cure Behavior of a Model Epoxy System by Means of TTT Diagram[J]. Journal of Materials Engineering, 2006, 0(5): 57-62.
Curing behavior of a model epoxies system (E-54/AG-80) with DDS as hardener was studied in this paper. Round disk compression mode DMA was executed to study the gel behaviors at different temperatures to determine the relationship between gel-time (tgel) and temperature. The cure kinetics was studied by dynamic DSC analysis. Parameters were obtained for establishing a phenomenological cure reaction model. The relationship between glass transition temperature (Tg) and cure degree (α) was also analyzed by both isothermal and dynamic DSC method based on DiBenedetto equation, which gave a mathematical description of Tg as a function of both time and temperature. Consequently, characteristic temperatures such as Tg0, gelTg and Tg∞ were determined. Finally, the Time-Temperature-Transition (TTT) diagram was designed based on the data and equations.
XIONG Tao, YANG Bin, XIONG Jie, XU Xian-jian, ZHOU Kai, MAO Ming-zhong. Effect of Strain Rate on Compression Behavior of Vinyl Ester Resin Casting[J]. Journal of Materials Engineering, 2006, 0(5): 63-67,72.
Quasi-static and high strain rate compressive experiments on vinyl ester casting were carried out by means of MTS (Material Test System) and Hopkinson bar. The behaviors of the compressed unstable and fracture of the resin casting at different strain rates were investigated.The results indicate that the response behavior of the resin casting is controlled by different mechanisms at different strain rate, and some mechanical properties of vinyl ester casting are rate-dependent: the casting are destroyed in toughness model under strain rate 3.3×10-4～6.6×10-3/s, while the casting are destroyed in brittleness model under strain rate 950～5800/s. The yield stress, yield strain energy density are all increased with the increasing strain rates at quasi-static as well as at high strain rates. What is interesting is that the yield strain decreased with the strain rates increasing at quasi-static while increased at high strain rates. It is considered that the casting occurred forcing high elastic deformation at high strain rates. The damage of the specimens is mainly controlled by axial stress before unstable deformation, while mainly controlled by shear stress after unstable deformation, and then developed to fracture finally. This progress is rate-dependent: the development of the cracks inside the castings increased with the strain rate increasing.
SHEN Zhen, CHEN Pu-hui, YANG Sheng-chun. Preliminary Study on Evaluation System of Capability of Composites to Withstand Impact[J]. Journal of Materials Engineering, 2006, 0(5): 68-72.
This paper summarizes the authors’ experimental study on the characterization system of composite behavior to withstand impact. The content includes: (1)The dent depth is the best parameter describing the impact damage state. (2) There exists the knee point phenomenon for damage resistance behavior (i.e. the relationship between impact energy or contact force and dent depth) and damage tolerance behavior (i.e. the relationship between dent depth and compressive failure strain or stress) of composite laminates. (3) The physical meaning of the knee point phenomenon is that the failure mechanisms change of damaged composites to fiber breakage in the first front plies from matrix crack and delamination. Some suggestions on the characterization system of composite behavior to withstand impact were proposed.
