Effects of rod size and fiber hybrid mode on the interface shear strength of carbon/glass fiber composite rods exposed to freezing-thawing and outdoor environments

Abstract Fiber reinforced polymer composite rod has attracted wide attentions to replace the steel rod as bearing component in bridge cable and underground oil extraction. In the present paper, three kinds of carbon/glass fiber reinforced polymer hybrid rods were developed to reveal the effects of rod size (19 and 22 mm) and fiber hybrid mode (core–shell hybrid and random hybrid) on the interface shear strength exposed to freezing-thawing and outdoor environments. Water uptake, mechanical, thermal properties and density tests were conducted to obtain the long-term evolution. The fiber random hybrid mode brought about a slight increase of water uptake compared to the fiber core–shell hybrid mode. The effects of temperature and temperature-alternating on the water uptake acceleration factors were remarkable compared to the hydraulic pressure and salty concentration. Furthermore, the increase of rod diameter prolonged the saturated water uptake time up to 81.4–136.9%. The obvious degradation of interface shear strength was attributed to the hydrolysis and plasticization of the resin owing to the water uptake and the microcracks formation. After drying, the remarkable recovery up to 20.3% of interface shear strength can be observed. Based on the long-term life prediction, the effect of temperature-alternating on the degradation of interface shear strength was more remarkable compared to the constant temperature, leading to the lowest stable strength retention of 38.7%. Furthermore, the rods with the fiber random hybrid mode and smaller diameter possessed the superior corrosive resistances, which provide the long-term design guideline in the application of bridge cable and underground oil extraction.