Effect Of Water Or Alkali Solution Immersion On Pultruded Carbon Fiber Reinforced Vinyl Ester Plates

Recently, carbon fiber-reinforced polymer(CFRP) composites are widely used for reinforcing structures, repairing or new construction, but due to the complex environment and long service life of the structures in the field of civil engineering, issues of the durability of FRP composites are increasingly prominent. Especially in humid or alkaline environment(such as the internal environment of concrete), the evolution of FRP’s long-term performance relates to the security of FRP reinforced structures.Vinyl ester resin has excellent water resistance, chemical resistance and other characteristics, and due to low viscosity, the processing performance is better than epoxy resin. Therefore, using temperature accelerated test method, the evolution and degradation mechanisms of vinyl ester resin and vinyl ester-based CFRP are studied in this paper, the study will promote the development of high durability CFRP composites and its application in civil engineering structures.Vinyl ester resin shrinks largely during the curing process; immersed in water or alkali solution,its water absorption meets the two-phase water absorption behavior; resin swells after immersion; under water immersion,the swelling strain is far less than the shrinkage strain; after immersion plasticization of the resin is obvious, ester bond of the resin hydrolyze, and alkali environment accelerates the hydrolysis reaction; under water, alkaline solution immersion the mechanical properties of the resin degrade,and alkaline solution immersion can accelerates the degradation of the resin’s mechanical properties.Immersed in water or alkali solution, water absorption of pultruded vinyl ester-based CFRP plates meets the two-phase water absorption behavior; resin matrix and carbon fiber-matrix bonding interface absorb moisture, and interfacial water absorption plays an important role. results of short beam shear test and in-plane Shear test show, water or alkali solution immersion leads to carbon fiber- resin interfacial adhesion properties irreversible degradation, and alkaline solution accelerates the degradation of interfacial adhesion properties. results of dynamic mechanical analysis and scanning electron microscope(SEM) verify the degradation of CFRP’s interfacial adhesion properties. The results of tensile test show, under water, alkaline solution immersion the mechanical properties of the vinyl ester-based CFRP degrade,and under alkaline solution immersion the degradation of its mechanical properties is more severe than the under water immersion. but eventually the value of tensile strength and tensile modulus stabilizes; in the beginning of the tensile test tensile strength of the pultruded vinyl ester-based CFRP are decided by the changes of matrix modulus and interface performance; with water absorption reaching quasi-dynamic equilibrium quality, the difference between inside and outside modulus of the pultruded vinyl ester-based CFRP decrease, at the same time shear stress of interface decreases, the tensile performance of the pultruded vinyl ester-based CFRP will be determined by the uniformity of tensile stress of all fibers.The vinyl ester resin has excellent properties of water resistance, alkali resistance,but interfacial properties degrade rapidly under water or alkaline solution immersion, the tensile properties are less affected, in order to improve the performance of the pultruded vinyl ester-based CFRP under water or alkaline solution immersion, It is important to study how to improve interfacial bonding properties, such as develop suitable sizing treatment agent of carbon fiber surface for vinyl esters.