This study experimentally examined the effect of nanomaterial on the tensile behavior of carbon fiber-reinforced polymer (CFRP) composites. Multiwalled carbon nanotubes (MWCNT), graphene nanoplatelets (GnPs), and short multiwalled carbon nanotubes functionalized COOH (S-MWCNT-COOH) with 1% by weight were used as the primary test parameters. In the present test, S-MWCNT-COOH was more effective than the others in improving the maximum tensile strength, ultimate strain, and toughness of the CFRP composites. The use of S-MWCNT-COOH increased the maximum tensile strength, ultimate strain, and toughness of the CFRP composites by 20.7, 45.7, and 73.8%, respectively. In addition, tensile tests were carried out for CFRP composites with S-MWCNT-COOH after subjection to elevated temperatures ranging from 50 to 200°C. The test results showed that the tensile strength, ultimate strain, and toughness were significantly reduced with increasing temperature. At a temperature level of 100°C, the reduction of the maximum tensile strength, ultimate strain, and toughness was 36.5, 37.1, and 60.0%, respectively. However, for the specimens subjected to the elevated temperatures ranging from 100 to 200°C, the tensile behavioral properties were constantly maintained. Finally, various analytical models were applied to predict the tensile strength of the CFRP composites with S-MWCNT-COOH. By using the calibrated parameters, the tensile strengths predicted by the models showed good agreement with the experimental results.

In the present study, the effect of harsh conditions on the tensile behavior of lap-spliced carbon fiber textile-reinforced mortar (TRM) with different surface treatment methods was investigated through the direct tensile test. The TRM coupons were exposed to three different harsh conditions: a chloride environment of 3.5 wt.% sodium chloride, a high temperature and humidity environment (50 °C and 95% relative humidity), and sustained load of 30% of the tensile strength during 60 days. In addition, two different surface treatment methods of the lap-spliced region of TRM coupons were used: carbon fiber textile impregnated by epoxy resin, and carbon fiber textile covered with aluminum oxide (Al2O3) powder after epoxy resin impregnation. The tensile characteristics of TRM coupons were investigated in terms of the cracking strength, ultimate strength, initial stiffness, and ultimate strain, to evaluate the influence of different surface treatment methods on the tensile behaviors of TRM coupons after exposure to various types of harsh conditions. Additionally, the test results were compared to the previous test results of TRM coupons that were not subjected to harsh conditions.

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