Effects Of Cryogenic Treatment On The Mechanical Properties Of Carbon-fiber And Glass-fiber Composites Under High Low Temperature Cycles

High Performance Fiber Composites are widely applied due to their characteristics of high strength,high modulus,high temperature tolerance,corrosion resistance and radiation shield,etc.Generally,high-performance fiber is always processed with other materials into composite instead of being used individually.By adding high-performance fiber reinforcement can greatly enhance product strength,reduce structural weight,extend service life and increase safety and reliability.Typically,in the fields of which the cycles of high and low temperature alternating change require the composite to have the good fatigue resistance and life durability.Cryogenic treatment is one of the promising methods for improving the property of metal tools at low-cost.This study introduced the cryogenic technique for surface and interfacial modification of high performance fiber and composites as a new research approach.Firstly,the two typical high performance fibers(Carbon fiber and Glass fiber)which were selected to be the reinforcement underwent cryogenic treatment both in Temperature-Programed Control Method(TPCM)and Quenching Method(QM).The untreated and cryo-treated composites were subjected to the tensile test and flexural test.The SEM was conducted to observe the surface morphologies of the untreated and cryo-treated composites.The results showed the increase of tensile and flexural properties of Carbon and Glass fiber/epoxy composites after cryogenic treatment.The bending strength of cryo-treated Carbon fiber/epoxy composite increased by 14.3%(QM).While,the mechanical properties of Glass fiber/epoxy composite were affected little by cryogenic treatment.The observation of the fracture surface showed improvement of interfacial bonding and reduction of delamination as well as fiber pull out.Secondly,in order to explore the effect of cryogenic treatment on the material,carbon fiber,glass fiber and epoxy resin were also treated by TPCM and QM.The surface properties,mechanical properties and internal structure of the fibers were characterized.The thermal properties and mechanical properties of the epoxy resin were tested.The results showed the increase of surface roughness and decrease of fiber diameter of carbon and glass fiber after cryogenic treatment.The IFSS of cryo-treated carbon and glass fiber with epoxy resin was increased by 29.5%(TPCM)and 32.7%(QM)respectively.While,the mechanical properties of Carbon and Glass fiber is affected little by cryogenic treatment.The glass transition temperature and mechanical properties of the epoxy resin were improved to some extent.The tensile strength and Young's modulus of the epoxy resin were increased by 13.4% and 29.4% respectively after the quenching process.The glass transition temperature was increased from 50? to 58? for TPCM and 60? for QM.Thirdly,this study also investigated the effect of cryogenic treatment on the mechanical properties of the two composites under the condition of high and low temperature with alternating cycles(0,25,50,75,100).The results showed that the mechanical properties of the composites increased and then decreased after high-low temperature cycling.The flexural properties reached the maximum at 50 cycles,in which the carbon fiber composite reached 651.63 MPa and the glass fiber composite reached 627.98 MPa.While the tensile properties were maintained at 25 cycles and then began to fall.Lastly,the effect of cryogenic treatment on the mechanical properties of carbon fiber composites and glass fiber composites after high-low temperature cycling was studied.The results showed that the mechanical properties of the composites after cryogenic treatment are more stable under different cycles of high temperature and low temperature.In conclusion,the cryogenic treatment technique has favorable effects on mechanical properties and high-low temperature cycling properties of these two kinds of high performance fiber composites.And this study will bring new vision to the surface modification of high performance fiber composites and is promising in research and market application.