Ultrasound-assisted Interlaminar Reinforcement And Mechanical Properties Of Composites

Composite materials have been widely used in aerospace,transportation and other fields because of their excellent properties.However,the unique structure of composite material is prone to crack in the interlayer after being impacted,and then layered damage occurs.Increasing the interlaminar strength of composites can effectively improve the impact resistance of composites,so the research on the toughening of composites has been paid more and more attention.This topic mainly studies the methods to improve the interlaminar strength of carbon fiber resin base composite plates and aluminum/carbon fiber laminated composite plates.Various methods are used to improve the interfacial bonding ability of composite materials so as to enhance the reliability of composite structure.The main research work of this paper is as follows:(1)With unidirectional carbon fiber prepreg as raw material,ultrasonic vibration assisted pretreatment process of water immersion was added before curing and forming of laminates.Under the condition of certain ultrasonic power,the water temperature in the ultrasonic process is controlled at 30?,and the components wrapped with waterproof film are placed in the ultrasonic generator.Four different ultrasonic time(20min,40 min,60min,and 80min)were used to measure the tensile properties and interlaminar fracture toughness of specimens,and to explore the relationship between ultrasonic time and the mechanical properties of carbon fiber laminated plates.At the same time,a fluorescent agent was applied in the middle of the laminates to observe the flow of the resin.The results show that the ultrasonic treatment does not affect the tensile strength of the specimen.In 40 min,power 500 w ultrasonic,under the optimum parameters of the ultrasonic pretreatment of its ? than untreated specimen fracture toughness increased by 32.6%.(2)Three different concentrations of carbon nanotube solutions(1%,2%,3%)were uniformly sprayed on the surface of carbon fiber prepreg.The effects of carbon nanotube concentration and ultrasonic pretreatment with water immersion on the interlaminar properties of carbon fiber laminates were studied.At the same time,the dispersion of MWNT with different concentration on the surface of carbon fiber prepreg and the state of the specimens after curing were observed.The experimental results show that the ultrasonic water immersion process and the addition of carbon nanotubes can effectively toughen the carbon fiber laminates.When the carbon nanotube concentration is 2%,the interlaminar shear strength of the specimen is202.4% of the untreated under the optimal ultrasonic assisted conditions of 50 min ultrasonic time and 500 W ultrasonic power.(3)Four different ultrasonic time(25 min,50 min,75 min,100 min)and ultrasonic power(200 W,300 W,400 W,500 W)were used to study the influence of ultrasonic pretreatment parameters of water immersion on the interface strength of Al/CFRP composites.At the same time,the adhesive area and microstructure of the resin on the aluminum plate were measured.The experimental results show that the water immersion ultrasonic vibration assisted pretreatment technology can effectively improve the fracture toughness of Al/CFRP,and the type I fracture toughness of Al/CFRP changes with the change of ultrasonic time and power.Under the optimal ultrasonic condition of 50 min of ultrasonic time and 500 W of ultrasonic power,the fracture property of the specimen and the bonding area between resin and aluminum plate increased by 126.8% and 62.3%,respectively,compared with the non-ultrasonic specimens.