Advances in Fracture and Failure Prevention

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Authors: Dong Su Bae, Dong Young Son, Sang Ll Lee, Hong Sik Park, Kwang Soo Kim, Jae Ho Jeon
Abstract: Four kinds of raw C/C composites with a density between 1.25~1.66g/㎤ were used in order to investigate the effect of the initial porosity of C/C composites on mechanical properties of liquid silicon infiltrated C/SiC composites. The microstructure observation, image analysis and flexural strength test of the composites were performed. The density and microstructural changes with the variation of the initial porosity was discussed in the terms of the infiltration behavior of liquid silicon and the reaction between liquid silicon and matrix carbon.
Authors: Yong Bum Choi, Jae Woong Jung, Won Jo Park, Sun Chul Huh, Kwang Yong Lee, Han Ki Yoon, Gen Sasaki
Abstract: 20 vol.% aluminum borate whisker (Al18B4O33w) reinforced AC4CH alloy composite was fabricated by squeeze casting method. The matrix is controlled its impurities, which make metal alloys, especially AC4CH alloy that is made by restraining 0.2% Iron and aluminum to make a matrix material. The perform of composite materials was made from Al18B4O33w with 5% regulated three kinds of inorganic binders, SiO2, Al2O3 and TiO2 sol, respectively and then sintered at 1373K. The composites were obtained by squeeze cast infiltration of the molten alloy to the perform. Then it was squeeze casting into the matrix. The status of adhesions of whisker perform was Observed by SEM. Micro-Vickers hardness and tensile properties at the room temperature were estimated. Al18B4O33w/AC4CH composites containing TiO2 sol has excellent properties on tensile properties and micro-vickers hardness compared with the other composites without inorganic binder, containing SiO2 and Al2O3 sol inorganic binder.
Authors: Li Song, Hong Jian Liao, Sheng Xing Wu
Abstract: This paper devoted to studying temperature joint in structures of reinforced concrete frame and bent. A nonlinear analysis program is made and improved specially for the study of reinforced concrete frame and bent under temperature load. Some reasonable values of joint distance are obtained for the frame and bent under high, middle and low temperature, and a design method of super-length reinforced concrete frame and bent under temperature load is presented.
Authors: Chul Kim, S. Hyun, M.H. Cho
Abstract: The shape changes by bending and twisting of a SMA/composite panel with embedded SMA wire actuators controlled by both electric resistive heating and passive elastic tailoring are investigated to realize the morphing wing of unmanned aerial vehicles. Three-dimensional finite element formulations are derived and used to analyze the behaviors of the SMA/composite smart structures. The numerical results show that the shapes of the SMA/composite panels can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring. To validate the analytical results, two SMA-embedded curved panels are fabricated and then, their changes in shape are measured by a laser optical sensor when SMA is activated by electrically resistive heating. Both results show excellent correlation.
Authors: K. Woo, Y. Suh
Abstract: In this study, the engineering properties were numerically calculated for laminated woven textile composites stacked with orientation angles. Single-field macroelements with modified sub-domain integration were used in the analysis to reduce computer resource requirement while efficiently accounting for the internal microstructure. A sample calculation procedure based on the Monte Carlo method was employed to consider the random tow arrangement due to shifted stacking between the layers. The effective properties were also calculated by the CLT and the results were compared.
Authors: Sang Ll Lee, J.O. Jin, Akira Kohyama
Abstract: The characterization of RS-SiC and RS-SiCf/SiC composite materials fabricated by the reaction sintering process has been investigated, based on the detailed examination of their microstructures. In this composite system, Tyranno SA SiC fiber and Hi-Nicalon SiC fiber were used as reinforcing materials. The green bodies for RS-SiC and RS-SiCf/SiC materials were prepared with the complex matrix slurry of SiC and C particles. The density and the room temperature strength of RS-SiC material with the starting SiC particles of 0.3 µm showed about 3.1 Mg/m3 and about 520 MPa, respectively, even if there were large amount of residual silicon (about 19 %). The flexural strength of Hi-Nicalon/SiC composites greatly decreased at the temperature higher than 1000 􀀀
Authors: Sang Ll Lee, J.O. Jin, J.S. Park, Jong K. Lee, Byeong Hyeon Min, Han Ki Yoon, J.Y. Park
Abstract: This study dealt with the characterization of MoSi2 based composites containing three types of additive materials such as SiC, NbSi2 and ZrO2 particles have been investigated, based on the detailed examination of their microstructures and fracture surfaces. The effects of reinforcing materials on the high temperature strength of MoSi2 based composites have been also examined. MoSi2 based composites were fabricated by the hot press process under the vacuum atmosphere. The volume fraction of reinforcing materials in the composite system was fixed as 20 %. The microstructures and the mechanical properties of MoSi2 based composites were investigated by means of SEM, EDS, XRD and three point bending test.
Authors: Dong Li Shi, Xi Qiao Feng, Yonggang Y. Huang, Keh Chih Hwang
Abstract: Owing to their superior mechanical and physical properties, cCarbon nanotubes (CNTs) seem to hold a great promise as an ideal reinforcing material for composites of high-strength and low-density. HOWEVER, In most of the experimental results to date, however, only modest improvements in the strength and stiffness have been achieved by incorporating carbon nanotubeCNTs in polymers. There are many factors that influence the overall mechanical property properties of CNT-reinforced composites, e.g. the weak bonding between CNTs and matrix, the waviness and agglomeration of CNTs. In the presentis paper, we use the Mori-Tanaka method to evaluate the effects of these factors on the moduli stiffness of CNTs-CNT-reinforced composites are examined. It is established found that the waviness and agglomeration may significantly reduce the stiffening effect of CNTs, while the interface adhesion between the matrix and CNTs has little influence the moduli of CNTs-reinforced composites little.
Authors: Yun Hae Kim, Soo Hyun Eum, Byung Kyu Choi, Jin Chun Kim, S.C. Kwon, P.K. Dutta
Abstract: Recently, composites are widely used for interior panel of the transportation facilities such as railway vehicle, ships and aircraft, etc. These interior composites panels are often made by vacuum bagging, hand lay-up method and autoclave, etc. In this study, we carried out tests for the evaluation of material properties of the panels under more severe conditions than real environment to evaluate the dimension stability of the interior composite panels. Two sets of panels, one made by hand lay-up method with glass mat/polyester resin (Type 1), and the other, by vacuum bagging method with epoxy prepreg/NOMEX (Type 2) are exposed to the low temperature, high temperature and room temperature. And then we measured the dimensions of the strained panels. To monitor the characteristics of cured resin, we used DSC (Differential Scanning Calorimeter). It was observed that Type 2 has higher mechanical properties and dimensional stability than Type 1.
Authors: Heoung Jae Chun, K.S. Ryu, Joon Hyung Byun
Abstract: An analytical model was proposed to predict the elastic properties of multi-axial warp knitted (MWK) fabric composites for three-dimensional structures. The characteristics of MWK fabric composites are the assemblage of multilayers of rovings in the warp, weft and bias directions for in-plane reinforcement and out-of-plane stitches by knitting rovings to provide through-the- thickness reinforcement. For analysis, a representative volume of the MWK fabric composite was identified. The geometric limitations, effects of stitch fibers and design parameters of MWK composites are considered in the model. Then, the elastic properties of MWK fabric composites are predicted by using an averaging method. The experiments are also conducted on the MWK fabric composites to compare the predicted results with the experimental results for the verification of suggested model. The predicted elastic properties are in reasonably good agreement with the experimental values. Finally the effects of design parameters of the MWK fabric composites are discussed.

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