Experimental Study On Impact Resistance Of Carbon Fiber Reinforced Cylinder

As the prices of fiber composites and their related materials have fallen sharply since the 1990 s,and as fiber composites have advantages in strength and ease of operation,carbon fiber composites(CFRP)sheet technology is gradually replacing the traditional reinforcement technology,becoming a new rising star in the field of building structure reinforcement,and the corresponding design standards have been promulgated in different reinforcement conditions.At present,the impact resistance of carbon fiber reinforced concrete structures under impact and other dynamic loads is lack of theoretical research,and few scholars are involved.However,due to the brittle fracture characteristics and anisotropy of the CFRP,there are hidden safety problems in the CFRP reinforced layer under low speed impact condition.Hence,it is of great practical significance and theoretical value to explore the dynamic response process,damage degree and mechanical behavior of concrete columns reinforced by carbon fiber under impact load,and then to understand the impact resistance of CFRP reinforced structures.In this paper,the impact device of the structural laboratory of Chang’an University is used to obtain the reinforced specimen under impact load The time-history curve of the contact force.the axial compression test of 21 specimens after impact damage was carried out under 5000 k N static load press.after the load-displacement curve,load-strain curve and typical failure morphology of the specimens were obtained,the impact resistance of concrete columns CFRP circumferential girdle was analyzed based on different parameters.The test results show that :(1)with the increase of the thick Ness of carbon fiber composites,the stiffness of the specimen increases,and the contact force extremum of the drop hammer after contact with the specimen becomes larger,but the damage failure of carbon fiber and the indentation depth of the hammer head decrease,the strain decreases with the increase of thick Ness,and the residual bearing capacity of the damaged column increases greatly.(2)The residual bearing capacity of the 18 specimens after impact damage is higher than that of the unreinforced specimens,indicating that the external carbon fiber cloth can effectively restrain the deformation of concrete columns,delay the failure and extension of concrete,and play the role of restraint and protection.(3)Concrete and CFRP as the impact mass of the drop hammer increases The failure state of axial and transverse direction is continuously expanded,and its residual bearing capacity is gradually reduced.but the contact force extreme value of the reinforced specimen increases first and then decreases,that is,there is a critical impact mass to make the contact force reach the extreme value.(4)The indentation depth of the drop hammer is proportional to the impact height of the drop hammer,and the residual bearing capacity is inversely proportional to the drop height of the drop hammer.Although the impact height will lead to the loss of the reinforcement effect of carbon fiber when the impact height is high,the direct on the plain concrete cylinder reduces the impact damage degree of the concrete in the contact position.(5)When the initial conditions of the impact are the same,the damage to the concrete column by the ball hammer is more serious,but The contact force extreme value of cylindrical hammer head is higher,and the residual bearing capacity of damaged column hit by spherical hammer is lower than that of damaged column hit by cylindrical hammer.(6)The level of loss of bearing capacity of reinforced specimens under impact is related to the degree of damage of carbon fiber cloth,but not to the strength of concrete.