TAILIEUCHUNG - Carbon Materials for Advanced Technologies Part 6

Tham khảo tài liệu 'carbon materials for advanced technologies part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 155 increasing X or Y fiber loading. However when the electrical resistivity was plotted as a function of the total fiber volume fraction a linear relationship was found. This demonstrates that impedance exists due to the high electrical resistivity in the fiber transverse direction and also explains why the electrical resistivity is higher in the Y direction. Table 8. Room temperature density p g cm3 thermal conductivity k W mK and electrical resistivity Q microhm-cm of various VGCF reinforced aluminum matrix composites. ID p Vf total X Y K X Y W mK Q X Y 1 0 397 225 2 20 6 339 287 3 193 356 265 TO 333 - - T1 0 534 - - T2 0 642 - - T3 0 406 - - VGCF - 1950 parallel 60 parallel to to fiber axis fiber axis 20a 100 perpendicular perpendicular to fiber axis to fiber axis Al - 200 4 a. Estimated value. Although VGCF A1 composite exhibits excellent thermal conductivity the mechanical properties are moderate. The average flexural strength and modulus of a 35 by volume VGCF A1 composite is about 150 MPa 22 ksi and GPa msi respectively. While the composites indicate relatively modest mechanical property values compared to composites reinforced with for example PAN fiber they are sufficiently robust to allow theh use in most applications where aluminum is satisfactory such as in most electronic packaging applications. In addition the CTE of aluminum about 22 to 25 ppm k can be dramatically reduced to less than 10 ppm K by the addition of VGCF. These data demonstrate the prospect of carbon fiber composites having several times the thermal conductivity of aluminum yet retaining lower mass and coefficient of thermal expansion promising to substantially improve composite performance while providing important weight savings. . Summary on VGCF composites The above data represent the first from composites fabricated .

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