Progresses in Fracture and Strength of Materials and Structures

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Authors: Hai Chang, Xiao Jun Wang, Ming Yi Zheng, Kun Wu
Abstract: Magnesium matrix composite reinforced with SiC particle was fabricated by compocasting method. The SiCp/AZ91 composite was extruded initially, then subjected to ECAP. The microstructure and tensile properties of the composite at ambient and elevated temperature were investigated. After ECAP, the matrix alloy was significantly refined due to the dynamic recrystallization occurred during ECAP. Both the ambient yield stress and ultimate tensile stress of SiCp/AZ91 were increased after 1-pass and 2-pass ECAP and decreased after 4-pass ECAP. The ECAP processed composite exhibited superplasticity at elevated temperature, which is mainly due to the grain refinement of matrix alloy. The dominant deformation mechanism of the ECAPed composite at high temperature was grain boundary sliding. However, the sliding was prohibited due to the present of SiC particle.
Authors: Chuan Hui Huang, Shi Bo Wang, Li Guo Liu
Abstract: This paper focuses on the effect of metal oxides on the mechanical properties of PA1010 composites, such as the tensile strength, compressive strength, shear strength and hardness. The experimental results show that the tensile strength of PA1010 composites filled with CuO and Al2O3 particles slightly decreases with the oxide contents increasing. However, the tensile strength of PA1010 composites filled with Fe3O4 particles increases, which has the average increment in tensile strength of 23.7% than the pure PA1010 materials. The results indicate that the compressive strength can be increased by adding CuO, Al2O3 and Fe3O4 particles into PA1010 polymer. The results exhibit that Fe3O4 particles have significant effects to increase the shear strength of PA1010 composites. However, Al2O3 particles filling reduce the shear strength of the composites.
Authors: Jin Feng Sun, Ming Zhi Wang, Xiao Pu Li, Zhan Wen He, Yu Cheng Zhao
Abstract: In this paper, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and sintering process were used to characterize Cu-Fe compound powders milled for different times. The increment of defects and the change of granularity, grain size and crystal structure were discussed. Mechanical Alloying (MA) influence on the sintering of Cu-Fe compound powders was analyzed. The results showed that, the refinement of the powders and the increment of defects such as interface and dislocation induced the energy storage. The stored energy released in the sintering process, which reduced the activation energy of vacancy and the activation energy of diffusion. So the sintering temperature was reduced and the structure, strength and hardness of specimens were improved.
Authors: Hao Ding, Yan Gai Liu, Yan Xi Deng, Ya Li Du
Abstract: The action mechanism between titanate and calcium carbonate in preparation of calcium carbonate/titanate composite material was studied by infrared spectrometry(IR) and X-ray photoelectron energy spectroscopy(XPS) analysis. The results show that adsorption of titanate could occur through chemical reaction with calcium carbonate surface. The chemical adsorption model of titanate on calcium carbonate surface was thus established on the basis of these analysis results.
Authors: Ya Li Du, Hao Ding, Yan Gai Liu, Yan Xi Deng
Abstract: The effects of technology condition and performance of calcium carbonate/titanate composite material (CCTCM) prepared by mechano-activated method were studied in this paper. The results show that CCTCM can be prepared by the surface modification of calcium carbonate using titanate as a modification agent incorporated with the simultaneous wet ultra-fine grinding, and the modification results and performance of composite material are affected by the grinding condition of calcium carbonate. CCTCM has good application characteristics from its physical property and the performance of packing polyethylene (PE).
Authors: Lin Jiang Wang, Xiang Li Xie, Da Qing Wu
Abstract: Kaolinite/formamide intercalation materials are characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FT-IR), Raman spectroscopy and 1H magic angle spinning nuclear magnetic resonance spectroscopy (1H MAS NMR). The d(001) spacing of kaolinite treated with formamide is 1.020nm, which is larger than that of the original clay. The 1H MAS NMR graphs show that the proton chemical shifts of the inner hydroxyl and inner surface hydroxyl of kaolinte are δ-1.3 and δ2.4 respectively. After formamide intercalation, the proton peaks of the inner surface hydroxyls shifted to high-field with δ2.3, the proton peak of the inner hydroxyl shifted to δ-0.3 toward low-field. In the hydroxyl stretching vibration region of Raman spectrum, the formamide intercalation resulted in the decrease of the intensities of kaolinite inner surface hydroxyl bands at 3699cm-1,3682cm-1, 3665cm-1 and 3642cm-1, and the appearance of additional bands at 3610cm-1,3628cm-1. In the NH stretching region of FT-IR spectrum, two bands are observed at 3336cm-1 and 3466cm-1 corresponding to the two types of the hydrogen bonds between formamide and kaolinite. In the carboxyl stretching region, an additional band at 1667cm-1 is assigned to C=O group that bonded to the inner surface hydroxyl of kaolinite.
Authors: Kui Chen, Rui Chen Yang, S.W. Cheng
Abstract: The thermal decomposition kinetics and thermal stability of poly (methyl methacrylate) (PMMA) and PMMA/ montmorillonite (MMT) nanocomposites containing 4 wt% MMT were researched by thermogravimetry (TG). The results show that, because of the barrier behavior of exfoliated MMT layer, the temperature of thermal decomposition of PMMA/ MMT nanocomposites is improved by about 10 °C, and thermal stability is improved by about double. The apparent activation energy of decomposition, calculated by Ozawa equation, of nanocomposites is higher than that of PMMA before 27 % mass loss.
Authors: Qing Cai Su, Jian Hong Gong, He Sheng Li, Bin Xu, Mu Sen Li, Ji Qing Zhao, Lu Chen
Abstract: Boron-doped diamond single crystals were synthesized with Fe-Ni-C-B System catalysts which content of boron carbide (B4C) were different, and their crystallographic features were tested with electron probe microanalysis (EPMA), X-rays diffraction (XRD), Raman spectrum and field emission scanning electron microscopy (FESEM). The experimental results showed that doped boron in the diamond could result in the changes of its crystallographic features. There were different X-ray peak intensities in the different boron-doped diamond crystals, and the intensities were changed with the content of B4C in the catalysts. With the increase of boron content in the diamond, the boron atoms resulted in the change of growing rate in different crystalline face of the diamond. The quality of diamond synthesized with catalyst which contained 0.2 w.t.% boron carbide was worse than others.
Authors: Supreyak Kumfu, V. Chailangka, Wim Nhuapeng, Pisith Singjai
Abstract: Carbon nanotubes (CNTs)/epoxy resin composites were prepared by using a sonication technique. Microstructure, mechanical and physical properties such as hardness, wear resistance, tensile strength and density of the composite samples were examined. The tensile strength of the 0.6 vol.% CNTs/epoxy resin composites compared with the monolithic epoxy resin increased 183%. The hardness and wear resistance were maximum at 0.8 vol.% CNTs. Moreover, SEM image of the composites indicated that there is good adhesion between CNTs and the epoxy resin.
Authors: Hao Ran Geng, Shou Ren Wang, Xin Ying Teng, Lin Hai Hui, Fu Song Xu
Abstract: One kind of 3DNMMC with different volume fraction reinforcement phase was fabricated by pressureless technique. The bending strength and fracture toughness were tested by 3-P bending strength experiments. When the volume fraction of reinforcement phase phase was not in excess of 10%, composites had an improvement of bending strength and fracture toughness owing to relatively homogeneous Al2O3 particle distribution encircled by metal matrix and the occurrence of interface reaction product as MgAlO2 spinel phase. Much and smaller craters and dimples are observed in metal matrix alloy and limited ductility of composites causes the early failure of composites. With the increases of volume fraction of reinforcement phase phase, crack characteristic consist of crack nucleation, growth, coalescence and crack propagation became the main fracture failure mechanisms.

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