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Ma R.,China Institute of Technology | Chang X.,China Institute of Technology | Liao Y.,Xian Aerospace Composites Research Institute | Zhang X.,China Institute of Technology
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2016

Comparative studies were carried out on the NOL rings of carbon fiber/epoxy composites cured by microwave (MW) curing technique and thermal curing technique. The curing behavior, microstructure as well as mechanical properties of cured composites were well investigated through a series of methods and equipments including FT-IR, micro-CT system, mechanical tension test machine and SEM. The results show that the curing mechanism for MW curing technique is different from conventional thermal curing technique and the cure cycle is greatly shortened. FT-IR measurements reveal that MWs do not initiate any new chemical reactions during the curing process and both MW and thermally cured composites have the same chemical structure. CT scan analysis indicates that the MW power used in the curing process has significant effect on the void content of cured composites. Moreover, the MW cured composites exhibit lower tensile and interlaminar shear strength as compared to thermally cured counterparts when using same curing temperature, which is mainly ascribed to the higher void content contained in the MW cured composites. Furthermore, the adhension between the fiber and resin is slightly better for MW cured composites compared with thermally cured ones, which is confirmed by SEM micrographs. © 2016, Editorial Board of Polymer Materials Science & Engineering. All right reserved.

Ji A.-L.,Northwestern Polytechnical University | Cui H.,Xian Aerospace Composites Research Institute | Li H.-J.,Northwestern Polytechnical University | Cheng W.,Xian Aerospace Composites Research Institute | Zhang X.-H.,Xian Aerospace Composites Research Institute
Guti Huojian Jishu/Journal of Solid Rocket Technology | Year: 2010

The property of pre-oxidation fiber and carbon fiber which are suitable for fabricating the carbon fiber preform in needling process was studied, and the property of felt preparation and needling was compared. After carbonization, the tensile strength of pre-oxidation fiber is only 2 000 MPa, which is lower than the carbon fiber(≥3 000 MPa). The elongation-to-break of pre-oxidation fiber is 4 times as high as that of carbon fiber, the needling fiber is 3~4 times as long as the carbon fiber, and the length of the needling pre-oxidation fiber is 8~15 mm. The peel strength of 3K carbon clothes/pre-oxidation fiber felt perform reaches 0.594 MPa, and that of 3K carbon clothes/carbon fiber felt perform is 0.128 MPa. With high deformation resistance and structural integrity, the carbon fiber needling preform is suitable for making the high strength thin structure, such as the divergent cone and the extendible cone of the rocket motor. For the thick C/C (C/SiC) composites structure, such as throat and divergent cone of tactical missiles, the pre-oxidation fiber is superior.

Wang X.-J.,Xian Aerospace Composites Research Institute | Hui X.-M.,Xian Aerospace Composites Research Institute | You L.-H.,Xian Aerospace Composites Research Institute
Yuhang Xuebao/Journal of Astronautics | Year: 2010

In this paper, cyanate ester, epoxy modified cyanate ester, epoxy resin and M40J composite's properties of water-enduring at 100°C were studied. The analysis of the rate of water uptake and the changes of mechanical properties before and after immersion was reported. It was found that cyanate ester and its modified system owned lower water uptake and had no apparent changes on mechanical properties. The rate of water uptake of composite is lower than that of the cast, but the tensile modulus and shear strength descend. The main reason is the interface is destroyed.

Ji A.-L.,Northwestern University | Cui H.,Xian Aerospace Composites Research Institute | Li H.-J.,Northwestern University | Cheng W.,Xian Aerospace Composites Research Institute | Ji L.-L.,Xian Aerospace Composites Research Institute
Xinxing Tan Cailiao/New Carbon Materials | Year: 2011

The structural characteristics of a carbon cloth/felt layer needled preform are investigated. X-Y direction tensile strength, Z direction peel-off stress, and the Naval Ordnance Laboratory (NOL) ring-integrated tensile strength were tested. The X-Y direction tensile strength decreased with the increase of needling density. The law of surface density of fiber felt affecting the Z direction stress is not obvious. Peel-off stress of a 3 K carbon cloth/felt needled preform is higher than that of 6 K and 12 K cloth/felt, and the peel-off stress of a diagonal carbon cloth/felt needled preform is better than that of a satin one. There are three different damage modes for the NOL-integrated tensile ring, namely complete rupture, incomplete rupture, and interlayer peel-off. For 3 K satin carbon cloth/felt needling preform, its NOL ring-integrated tensile strength is the lowest and only 3 MPa, and it shows complete rupture. For the 12 K satin carbon cloth/felt needled preform, the damage mode is interlayer peel-off, and for the 6 K satin carbon cloth/felt needled preform, the damage mode is incomplete rupture, and its integrated mechanical performance is excellent. NOL ring-integrated tensile strength is much higher than X-Y tensile intensity for the preforms made by same process.

Zhang S.-h.,Northwestern Polytechnical University | He G.-q.,Northwestern Polytechnical University | Liang G.-z.,Northwestern Polytechnical University | Cui H.,Xian Aerospace Composites Research Institute | And 2 more authors.
Applied Surface Science | Year: 2010

A comparison of F-12 aramid fiber with domestic armid fiber III (DAF III) on surface feature was carried out by scanning electron microscope (SEM), atomic force microscopy (AFM), elements analysis and X-ray Photoelectron Spectroscopy (XPS) analysis. It is found that the two aramid fibers are of "skin-core" structure and fibrillar structure. The microfibrils orient along the fiber axis and rather poorly bond in transverse direction. Many defects exist on the surface of two fibers. Carbon, hydrogen, nitrogen and oxygen are the major elements of two aramid fiber. The element content of the same aramid fiber from surface to interior is different. The surface carbon contents of F-12 aramid fiber and DAF III are increased by 10.75% and 9.95% than those in fiber interior respectively, the surface nitrogen content decreased by 9.72% and 27.02% respectively, and the surface oxygen content increased by 13.99% and 37.95% respectively. © 2009 Elsevier B.V. All rights reserved.

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