Evaluation and prediction of temperature-dependent tensile strength of unidirectional carbon fiber-reinforced polymer composites

To predict temperature-dependent tensile strength of unidirectional CFRP composites, numerical analysis and model simulation were conducted in terms of experimental results. The effect of elevated temperatures on tensile strength of CFRP sheets was evaluated between 20 degrees C and 120 degrees C, and the storage moduli of two types of epoxy resins, with glass transition temperatures (T(g)) of 42 degrees C and 45 degrees C, were tested by DMA. The tensile experiments of CFRP sheets show that the tensile strength exhibits stable behavior at the low-temperature range (below glass transition temperature), but drops rapidly during the glass transition region, and then reaches a plateau. Analysis results indicate that the degradation of tensile strength is mainly due to matrix softening and loss of fiber-matrix adhesion, based on which a semi-empirical model is proposed to precisely describe tensile strength reduction as the temperature increases. The parameters of the model consist of the glass transition temperature of polymer matrix, the polymer glass transition region, and the residual strength after the glass transition region. Model prediction of tensile strength vs. temperature shows good agreement with the experimental results.