Experimental Studies on the Elastic Properties of Carbon Fiber Reinforced Polymer Composites Prefabricated of Unidirectional Carbon Fiber Fabrics and a Modified Rule of Mixtures in the Parallel Direction

Carbon fiber (CF) fabrics can be installed manually onto the surfaces of existing structural members to establish a carbon fiber reinforced polymer (CFRP) reinforcemenet system, even in areas of limited access. Actual mechanical properties, such as the ultimate tensile strength (UTS), elastic modulus (EM), and ultimate rupture strain (URS), are essential for application in engineering practice and theoretical analysis of CFRP strengthening system. In this study, 16 CFRP strips were prefabricated of unidirectional CF sheet by a wet lay-up technique, and were tested to evaluate their elastic parameters. Test results indicated that experimental values of all specimens were much lower than that of CF fabrics, which were provided by manufacturer, and the stress-strain curves were observed to deviate slightly from a perfectly linear relationship at the later stage of loading. Comparing with the predictions of the rule of mixtures (ROM), the experimental data have large deviations and opposite laws. An orientated-design model was derived to modify the linear ROM by the regression analysis. A modified rule of mixtures (MROM) was suggested to describe the elastic properties of CFRP composite in the parallel direction