Uncoated Carbon Trc Lab Report

The effect of elevated temperatures on the coated carbon TRC tensile strength is shown in Figure 10. The mean results of strength, strain and elastic modulus (at 7 days of age + heating and cooling process) are given in Table 4. The values, as well as the standard deviations, refer to three TRC test specimens. As well as in the uncoated carbon TRC, a strain-hardening behavior is clearly observed in the stress-strain curves up to 400°C. Although not impregnated by matrix, the coated carbon TRC presented higher tensile strength than the uncoated TRC at room temperature (Figure 10a). This behavior occurs due to the coating’s impregnation which acts mechanically activating equally part of the filaments present in the carbon yarns. In the uncoated
In relation to the ultimate tensile strength (σUTS) obtained at room temperature, the decreases induced by the thermal treatment in the coated carbon TRC were, respectively, 50.8%, 62.2% and 85.4% for temperatures of 200°C, 400°C and 600°C. Through Tables 3 and 4 it is possible to verify that the σUTS values obtained for the uncoated carbon TRC under imposed temperature (200°C and 400°C) were, on average, about 1.7 times greater than that obtained for the coated ones. The relation was not computed for 600°C given the absence of post-cracking response. In comparison with the results obtained at room temperature, the decrease in the elastic modulus for the temperatures of 200°C, 400°C and 600°C were 44.8%, 77% and 83.7%,
At 400°C, it was observed thermal cracking in the refractory matrix, while carbon fibers kept their cylindrical shape and smooth surface. As shown in Figure 12d, at 600°C the fibers were compromised by the oxidation process which resulted in surface flaws, rupture and decrease of the fiber cross sectional