Mechanical properties and oxidation behavior of carbon/carbon composites based on static and dynamic mechanical thermal analysis methods
In this study,three-point bending and dynamic mechanical thermal analysis(three-point bending mode)have been used to test the mechanical and damping properties of C/C composite materials at different temperatures.In addition,the specimens have been oxidized at 350℃for different hours in a furnace,and its morphology after oxidation has been investigated as well.From the results,it was found that the flexural strength and modulus of specimens at room temperature are 671.6 MPa and 44.3 GPa,respectively.When the temperature of testing was raised to above 300℃,the strength and modulus significantly dropped to 41.5 MPa and 4.7 GPa,respective-ly.The results of DMA show the same trend to three-point bending.The modulus of specimens is 45.9 GPa at room temperature tested by DMA,and the modulus of specimens has dropped to a very low level as the temperature reaching above 300℃.On the other hand,there is a damping peak found at 210℃,and the tanδ was determined as 0.14 at 210℃.In addition,after 72 hours of oxidation,the weight loss rate of the material reaches about 7.5%,and the bending strength and the modulus degradation are about 72.1%,27.8%,respectively.Finally,the morphology of oxidized specimens showed that the gap between fibre and matrix gets wider as the increase of oxidation time,and the matrix of carbon is severely oxidized,the remaining of matrix carbon keeps a significant low level compared to untreated specimens.Besides,the oxidized fibres show a coarse surface and cross section,and segregations of contaminations also can be found at oxidized fibres.
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