| Basalt fiber reinforced polymer(BFRP)composite is an environmentally friendly material.It has high cost-performance-ratio,good corrosion resistance and superior mechanical properties like good fatigue resistance.It is increasingly used for reinforcement spearially in the structures of special requirements(anti-radar interference or sensitive electrical test equipment structure),in the constructions in the complex corrosive environment of salt lake,seaside and in the long-span bridges which bear some long-term fatigue load.With the increasing requirements in corrosion resistance and fatigue performance of engineering structures worldwide,enhancing the corrosion and fatigue resistance of BFRP is essential for its future development of civil engineering.Base on the previous studies,the corrosion and fatigue resistance of BFRP have a great relationship with the interface layer between the matrix and the fiber.Accordingly,this paper developed and investigated two methods to improve those resistance of BFRP:First,the matrix was improved by using a high performance thermoplastic resin.The BFRP with thermoplastic epoxy resin had lightweight,high strength,good corrosion resistance,good toughness and could have secondary processing molding to solute the problem of on-site bending for existing thermosetting FRP tendons.Comparing with the thermosetting epoxy BFRP,the advantages of thermoplastic epoxy BFRP were evaluated by studying the corrosion resistance and fatigue resistance of thermoplastic epoxy BFRP and its corrosion resistance mechanism and fatigue mechanism.Second,coating treatment of basalt fiber was used to improve the interface performance and the degradation of the BFRP with different resin base types in the corrosion solution was studied and compared with the untreated BFRP.The main research contents are as follows:1.The curing process of thermoplastic epoxy resin was studied.This paper developed a production process of thermoplastic epoxy resin specimen and determined the preprocessing procedure(the curing temperature,curing time and mold release agent of thermoplastic epoxy resin)to solve the impregnation of roving and fiber cloth by the thermoplastic epoxy resin through several trial tests.Through a large number of the tensile tests of thermoplastic epoxy BFRP sheets,the resin of anchoring was selected as the thermoplastic epoxy resin.The process and the specific operation flow of the thermoplastic epoxy resin-based BFRP impregnated yams,sheets and fatigue sheets were developed;2.The static tensile properties of thermoplastic epoxy resin,thermoplastic epoxy BFRP impregnated yams and BFRP sheets were measured.It was also compared with the tensile properties of the thermosetting epoxy resin,BFRP impregnated yarns and BFRP sheets.The results showed that the thermoplastic epoxy resin and the thermoplastic epoxy based BFRP had great tensile strength and ductility;The effects of different temperatures,different aging days and different corrosion solutions on the corrosion degrees of thermoplastic epoxy resin-based BFRP sheets were studied.The results showed that the mechanical properties and corrosion resistance of BFRP were obviously improved when the thermoplastic epoxy resin was used as the base material.The thermoplastic epoxy resin-based BFRP had the lowest corrosion degree at room temperature(25?)and the acid resistance was the same with the alkali resistance at this temperature.In the 40 ? and 55 ?,acid resistance was greater than alkali resistance and BFRP had a higher long-term life in the acid solution;3.The tensile strength of the basalt fiber roving before and after the coating was measured and the degree of degradation in the 80 ? alkali corrosion solution was tested.The results showed that the coating had good bonding effect with the infiltration agent.The fracture strength of the coating treated basalt fiber was higher,the alkali resistance was better.The retention degree of alkali corrosion is 2 times of that of untreated;The tensile strength of the impregnated yarns of thermoplastic resin,thermosetting epoxy resin,ordinary vinyl resin,alkali resistant vinyl resin,toughening alkali-resistant vinyl resin and treated with basalt fiber was tested after immersed at 80 ? alkaline solution.The results showed that the existence of coating obviously reduced the degradation rate of BFRP in corrosive solution by comparing the tensile strength of the uncoated BFRP impregnated yarn before and after the corrosion.BFRP after treating improved the retention rate of 20%-30%.The coating had obvious effect of improving alkali corrosion resistance of BFRP;4.The thermoplastic epoxy BFRP sheets were tested under fatigue load of a fixed stress ratio.The number of fatigue failure,the stiffness degradation and the fatigue damage were monitored and compared these properties of the thermosetting epoxy BFRP.Life prediction methods were also developed on reliability analysis.The results showed the fatigue life of thermoplastic epoxy BFRP was about the same as that of thermosetting epoxy BFRP at high stress levels.But at low stress level,the fatigue life of the former is much higher than that of thermosetting epoxy BFRP.The S-N curve of the former is lower;All of the fatigue life predicted based on reliability analysis by the stress level of the thermoplastic epoxy BFRP was higher than that of the thermosetting epoxy BFRP;The stifness degradation mode of the thermoplastic epoxy BFRP and the thermosetting epoxy BFRP is roughly the same,but the former has higher critical limit stiffness and less stifness degradation rate than the latter;The thermoplastic epoxy BFRP had two kinds of damage patterns of fatigue damage,which were the damage pattern of fiber fracture under high stress level and the damage pattern of matrix cracking and interface debonding at low and medium fatigue stress levels.The accumulation and development of microcracks of thermoplastic epoxy BFRP were very slow by comparing the fatigue damage of the thermosetting epoxy resin BFRP,so that the thermoplastic epoxy BFRP had a higher fatigue life at the same stress level. |
PDF Full Text Request