Development of Long-Term Performance Evaluation Criteria for Construction CFRP Composite Materials

This study serves as a preliminary investigation to develop a method and criteria for the long-term performance evaluation of construction CFRP composite materials produced in Korea, specifically focusing on regulating the fatigue failure of these materials. To achieve this, a 4-point flexural test was carried out based on ASTM D6272, and five specimens were fabricated with dimensions of 300 mm in length, 240 mm in effective length, and 20 mm in width, using the shape specified for coupon tests to concentrate stress at the center of the specimen. Flexural–tension tests were conducted by applying a 5-mm displacement load and controlling the frequency at 4 Hz. This method is based on the displacement calculation formula proposed in ASTM D7774 and ensuring that it does not exceed the material's proportional limit as specified in ASTM D6272. The performance evaluation criteria for this test were categorized into three cases based on ACI 355.2-01: cycles at 80% reduction in stiffness, cycles at 70% reduction in stiffness, and cycles at the inflection point. It was observed that the cycle count for the case with an 80% reduction in stiffness occurred 39.76-94.27% faster than the other two conditions. Furthermore, based on ASTM D7774, which stipulates fatigue failure criteria for plastic materials when stiffness decreases below 90%, this study established long-term performance criteria for Korean construction CFRP composite materials at 80% stiffness to enhance field testing efficiency and reduce testing time.