Effect of high pressure and temperature immerson on the properties of the glass-carbon hybrid FRP composites

The durability of hybrid rod at different temperatures and hydrostatic pressure was studied experimentally. Interface bond strength of carbon fiber/epoxy, glass fiber/epoxy and CFRP/GFRP was evaluated. The water uptake and T_g were used to reveal the degradation mechanism of interface properties. The interface bong strength of fiber and epoxy depend on the post-curing effect in the epoxy and water molecule. When the hybrid rods were immersed into water for some time, the post-curing effect in the epoxy improved the Van der Waals and hydrogen bonds in the epoxy. Furthermore, the cross-linking effect between fiber and epoxy was strengthened, which led to the increase of interface bond strength. Besides, high temperatures accelerated water molecule spreading to the interface of fiber and epoxy, leading to the de-bonding between the fiber and epoxy. The exposure time was significant on the post-curing effect in the epoxy and when exposure time was up to 180d, the post-curing effect was almost completed. The water pressure accelerated the water absorption of the hybrid rod. It created the confinement effect from the skin layer to core layer of hybrid rod, increasing the chemical bond and interface bond strength of glass fiber and epoxy and had little influence on the carbon fiber and epoxy.