Tensile Behavior of Unidirectional Pultruded Polyfunctional Epoxy Resin‐Based <scp>CFRP</scp> Plates at Elevated Temperatures: Experimental Investigation, Strength Prediction, and Constitutive Model

ABSTRACT Understanding the tensile behaviors of unidirectional carbon fiber reinforced polymers (UD‐CFRP) at elevated temperatures is crucial for the safe design of CFRP components. In this study, pultruded polyfunctional epoxy resin‐based CFRP plates were prepared. The softening ( T g ) and thermal decomposition ( T d ) temperature of CFRP plates tested by Dynamic Mechanical Analysis (DMA) were 217.16°C and 298.78°C, respectively. The tensile tests within the temperature range of 20°C–350°C and microscopic characterization were conducted. The failure modes, stress–strain curves, tensile strength, and elastic modulus at the temperature range were revealed. The results indicated that the softening and thermal decomposition of the resin matrix contributed to the differences in tensile behaviors of CFRP. Within the temperature range of 20°C–180°C, the tensile elastic modulus and strength retention of CFRP remained above 90% and 87%, respectively, owing to the great thermal properties of the resin matrix. Besides, CFRP plates showed explosive fragmentation failure mode at the temperature range. When the temperature approached T g and T d , the tensile strength retention decreased to 61.54% and 47.19%, respectively, due to the degradation of the resin matrix and interface, and the uneven and independent fractures of fibers. According to the tensile strength evolution, a temperature‐dependent strength prediction model was established. Besides, a tensile constitutive model considering both critical temperature points and fiber fractures was established.