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148 results on '"He Jun"'

35. Performance analysis of a carbon cloth/felt layer needled perform

Author

Hong Cui, He-jun Li, A-lin Ji, Ling-ling Ji, and Wen Cheng

Subjects
Materials science, Materials Science (miscellaneous), chemistry.chemical_element, General Chemistry, Stress (mechanics), Complete rupture, chemistry, parasitic diseases, Ultimate tensile strength, General Materials Science, Fiber, Composite material, Layer (electronics), Carbon, Intensity (heat transfer)
Abstract

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 3K 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 6K 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.

Published
2011

44. The thermal expansion behavior of 3D C/C composites

Author

He-jun Li, Kezhi Li, Guo-Dong Sun, and Xiao-ling Liao

Subjects
Materials science, Composite number, Carbon fibers, General Chemistry, Atmospheric temperature range, Microstructure, Thermal expansion, Negative coefficient, visual_art, Chemical vapor infiltration, visual_art.visual_art_medium, Carbon composites, General Materials Science, Composite material
Abstract

Three dimensional braided carbon/carbon composites (3D C/C composites) were fabricated by chemical vapor infiltration. The thermal expansion behavior of these materials with various densities before and after heat treatment was investigated. It is found that PAN-based carbon fibers (CFs) have an obviously negative coefficient of thermal expansion (CTE) after heat treatment at 1 200 ℃. The CTE of the 3D C/C composites is negative from room temperature to 100 ℃ and is proportion to their density. In the temperature range of 100-1 000 ℃,CTE vs. T curves have an almost a constant slope and expansion behavior of the composite is similar to that of pyrocarbon. When the temperature is above 1 000 ℃,a peak is found in the CTE vs. T curves,indicating that expansion of the pyrocarbon is limited by CFs and the thermal expansion behavior of the composites is determined by both CFs and matrix.

Published
2010

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