A study on the variation of the orthotropic properties of T800 carbon/epoxy composites according to the forming pressure

초록

In this paper, in order to investigate the basic mechanical property and the variation of mechanical property of T800 carbon/epoxy composites according to the forming pressures, the various tensile tests were done for the in-plane mechanical properties such as E1, E2, G12 and Poisson ratios according to the international testing standards (ASTM 3039 for the unidirectional properties and ASTM 3518 for the bias extension test for in-plane shear properties). The Iosipescu test was also carried out for the out-of-plane mechanical properties. The test specimens of all the tests were fabricated by an autoclave de-gassing molding process controlling the forming pressures (absolute pressures of 0.1MPa, 0.3MPa, 0.7MPa including vacuum). For the tensile test specimens the cured composite laminates were cut by water jet cutting machine in size and for the out-of-plane shear specimens the V-notch was precisely machined by a milling machine. Fiber volume fractions of all the specimens cured by different forming pressures were also measured to find out the correlation between the property variation and the forming conditions. Matrix digestion method (ASTM 3171) using 70% nitric acid was used to minimize the damage of fibers. From the test results, the orthotropic properties of the T800 carbon/ epoxy composites were measured and compared under the different forming conditions. And these basic properties can be used in design machine elements such as high pressure vessels.

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