Study On Corrosion Damage Behavior Of Carbon Fiber Reinforced Bismaleimide Resin Composites

Composite materials are widely used in the construction of important structures in the field of aerospace because of their advantages of lightweight structure,high mechanical properties and good corrosion resistance.In northwest China,as the largest energy producing area,oil and gas resources exploitation has been advancing to the depth.ultra-deep well,ultra-high temperature,ultra-high pressure and strong corrosive medium lead to extremely harsh service conditions for tubing,which puts forward higher requirements for downhole pipe string material properties.This paper attempts to verify the feasibility of the application of carbon fiber reinforced bismaleimide resin composite tubing with the advantages of lightweight and corrosion resistance,and to study the corrosion damage behavior of carbon fiber reinforced bismaleimide resin composite in the laboratory simulation oilfield environment,so as to provide data support and theoretical guidance for oilfield engineering applications.In this paper,immersion test method is used to explore the diffusion behavior of oilfield produced water in composite materials,explore the influence of oilfield water medium on the mechanical properties of composite materials,and study the corrosion damage mechanism of composite materials in oilfield water medium.The corrosion damage behavior of composite materials soaked in oilfield water was studied by chemical composition,thermal stability and mechanical properties testing methods combined with fracture morphology observation.The results show that water diffusion has a promoting effect.Pure water and produced water had no effect on the thermal stability of the resin,but the local dissolution of bismaleimide resin was promoted with the increase of temperature.The main reason for the degradation of mechanical properties of composite materials is that oil field water dissolves and damages the bismaleimide resin on the surface of composite materials.Meanwhile,oil field water diffuses into the interior of composite materials and causes swelling of composite materials,which leads to stress concentration at the fiber/resin interface and damages the interface structure.At the same time,due to the influence of dissolution and swelling behavior,the mechanical properties of the composite materials will be attenuated to a certain extent under the condition of temperature rise.An autoclave was used to simulate the high temperature and high pressure environment of the oilfield in the laboratory to study the influence of the combined action of hydrostatic pressure and temperature on the corrosion damage behavior of the composite materials in the oilfield produced water.Under the combined action of pressure and temperature,the corrosion rate of composite materials is accelerated,and only slight oxidation occurs on the surface of resin at low temperature.When the temperature rose to 210 ℃,the matrix of the resin surface oxidized chemical reaction occurred to a certain extent,and bismaleimide resin reacted with the oil field water to form new groups-C-O-and-C=O.Chemical corrosion occurs on the surface of bismaleimide resin to a certain extent,and the combined action of pressure and temperature will accelerate swelling and destroy the integrity of the interface between fiber and resin,resulting in the mechanical properties of composite materials to a certain extent.The results show that the mechanical properties of carbon fiber reinforced bismaleimide resin composites are still within the allowable range and meet the requirements of long-term safety service when the performance loss is not higher than 160 ℃.