Combined effects of sustained bending loading, water immersion and fiber hybrid mode on the mechanical properties of carbon/glass fiber reinforced polymer composite

Fiber reinforced polymer composites have great potential to replace steel for bridge cables, underground oil extraction and ocean engineering owing to light weight, high strength and desirable corrosion and fatigue resistances. How to reduce the material cost and improve the durability through the reasonable material design is significant to promote the engineering application. In the present paper, two kinds of carbon/glass fiber hybrid plates were developed including the fiber random hybrid (RH) and core-shell hybrid (CH) modes. The exposure of sustained bending loading and water immersion as long as 360 days was conducted to investigate the effect of fiber hybrid mode and bending loading on the mechanical properties. The results showed the synergetic effects between the carbon and glass fibers can be fully developed through the random fiber hybrid mode. Furthermore, the incongruous bearing behavior and stress concentration of carbon/glass fiber/resin interface were largely relieved, which contributed to higher mechanical properties. Compared to CH plate, the maximum increase percentages of tensile and flexural strength for RH plate after 360 days were 51.3% and 39.7%, respectively. Higher bending loading level resulted in the fast formation of microcracks, which provided more storage space for the water molecule and accelerated the resin hydrolysis and interface debonding of fiber/resin. Finally, the long-term life prediction of hybrid plate in three typical bridge service environments showed the RH plate has superior corrosive resistance compared to CH plate. The retentions of tensile and flexural strength for the service time of five years were close to 30-40% and 50-60%, which provided the durability guideline based on fiber hybrid design for the engineering applications.