EXPERIMENTAL STUDY ON FATIGUE DAMAGE EVALUATION OF GFRP USING PARALLEL PLATE CAPACITORS

Abstract

 GFRP (Glass Fiber Reinforced Polymers) possesses excellent strength-to-weight ratio and durability. However, there are still many uncertainties surrounding the evaluation of damage in GFRP. Particularly, small cracks in the resin and delamination due to fatigue damage are challenging to detect visually. Therefore, this study focuses on investigating a fatigue damage evaluation method using capacitance. Initially, authors conducted a tensile fatigue test on a specimen with electrodes bonded to both sides of the GFRP. This test revealed that the occurrence of cracks in the resin, which is an early sign of fatigue damage, does not affect the capacitance. Following this, authors created a GFRP with electrodes embedded inside and conducted tensile fatigue tests to investigate the relationship between capacitance, the number of cycles, and residual stiffness. The experiment demonstrated that the capacitance decreased as delamination progressed from the middle of the fatigue life onwards. This finding indicates that it is possible to evaluate fatigue damage based on the decrease in capacitance. However, the experiment also highlighted the importance of ensuring the durability of the electrodes themselves.