Fatigue behavior and failure mechanism of basalt FRP composites under long-term cyclic loads |
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| Affiliation: | 1. National and Local Unified Engineering Research Center for Basalt Fiber Production and Application Technology, International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China;2. Key Laboratory of C & PC Structures Ministry of Education, Southeast University, Nanjing 210096, China;3. Composites Division, Jiangsu Green Materials Valley New Material T&D Co., Ltd, Nanjing 210019, China;1. Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;2. State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;1. Department of Civil Engineering, Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013, China;2. Department of Civil and Environmental Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA;1. Civil Engineering Department, Universidade Federal Fluminense, Rua Passo da Patria 156, Bloco D, Niterói, CEP 24210-240 RJ, Brazil;2. Civil Engineering Program - COPPE, Universidade Federal do Rio de Janeiro, C.Postal 68506, CEP 21941-972, RJ, Brazil |
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| Abstract: | This paper studies the fatigue behavior of basalt fiber reinforced epoxy polymer (BFRP) composites and reveals the degradation mechanism of BFRP under different stress levels of cyclic loadings. The BFRP composites were tested under tension–tension fatigue load with different stress levels by an advanced fatigue loading equipment combined with in-situ scanning electron microscopy (SEM). The specimens were under long-term cyclic loads up to 1 × 107 cycles. The stiffness degradation, S–N curves and the residual strength of run-out specimens were recorded during the test. The fatigue strength was predicted with the testing results using reliability methods. Meanwhile, the damage propagation and fracture surface of all specimens were observed and tracked during fatigue loading by an in-situ SEM, based on which damage mechanism under different stress levels was studied. The results show the prediction of fatigue strength by fitting S–N data up to 2 × 106 cycles is lower than that of the data by 1 × 107 cycles. It reveals the fatigue strength perdition is highly associated with the long-term run-out cycles and traditional two million run-out cycles cannot accurately predict fatigue behavior. The SEM images reveal that under high level of stress, the critical fiber breaking failure is the dominant damage, while the matrix cracking and interfacial debonding are main damage patterns at the low and middle fatigue stress level for BFRP. Based on the above fatigue behavior and damage pattern, a three stage fracture mechanism model under fatigue loading is developed. |
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| Keywords: | Basalt fiber SEM Fatigue Damage mechanism |
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