Study On The Thermal Effects On Interface Of Carbon Fiber Reinforced Composites

Interface is an important component of carbon fiber reinforced polymer composites(CFRPs)and has a significant effect on the overall material performance.Therefore,interfacial characterization has always been a key field for CFRPs research,among which microscopic characterization is a research hotspot.The interfacial performance of CFRPs can be destroyed by thermal effects,such as electric thermal effect and hygrothermal effect while the mechanisms are not clear.Studying the effects of these thermal effects on CFRPs is helpful to prevent the damage of materials in practical use.The specific studies are as follows:(1)Electrical currents were applied on CFRPs monofilament samples.Microscopic infrared spectroscopy was used to characterize chemical structure of resin near the interface,Raman spectroscopy was adopted to analyze the interfacial stress,and single-fiber fragmentation test was used for analyzing the interfacial shear strength.And effects of current on the chemical structure and thermal stability of CFRPs monolayer were studied by total reflection infrared spectroscopy and thermogravimetric analysis.The results showed that 6 mA current treatment caused additional cure of resin within 70 um from the fiber.With the increase of the current from 0 mA to 6 mA,the interfacial compressive stress increased first and then decreased,while the interfacial shear strength increases gradually.As the current increased,post cure,breaking of ether bond and dehydrogenation occurred in CFRPs monolayer in turn.Moreover,thermal stability of the monolayer decreased significantly when the current reaches 1.4 A.(2)Hygrothermal treatment and heat treatment were carried out for CFRPs respectively.Morphology changes of the CFRPs were quantitatively analyzed by atomic force microscopy(AFM).Interlaminar shear strength of the CFRPs was analyzed by short beam shear test.It was indicated that the hygrothermal treated samples had larger resin shrinking extent between fibers,the smaller effective bonding area toward resin and the higher shrinking extent in the range of 0.5 ?m from the fibers.In addition,the interlaminar shear strength of the hygrothermal treated CFRPs decreased by about 12% and had the more severe fiber debonding within each layer.(3)After ethanol treatment,the CFRPs were observed by an environment control scanning probe microscope with in situ heating and the influence of solvents on the mechanical properties was analyzed by short beam shear test.The results showed that the resin around the interface expanded after the treatment.With heat treatment,the resin shrinkage and fiber expansion occurred remarkably in the ethanol treated CFRPs.However,mass,interlaminar shear strength and corresponding failure modes of CFRPs laminates weren't significantly affected by ethanol treatment.