Study On Atomic Oxygen Erosion Resistance For The Interface Of BAPPO-modified Carbon Fiber/epoxy Composites

Carbon fiber/epoxy composite materials have excellent performance and widely used in a variety of spacecraft. But the spacecraft will be subject to atomic oxygen erosion when it running near-Earth orbit. So that using atomic oxygen protection to extend restricting spacecraft survival time is becoming a research project. In recent years, through the introduction of containing aromatic benzene phosphorus oxide structure(PPO) to greatly improve the resistant to atomic oxygen molecule properties. This paper uses three methods to study the interface between carbon fiber and epoxy resin resistant to atomic oxygen performance: The use of bis(3-amino) phenyl phosphine oxide(BAPPO) and epoxy resin compounds sizing on the fiber surface, carbon fiber surface grafting BAPPO method, the carbon fiber surface secondary graft POSS method.Use the sizing method modification the interfacial properties of carbon fiber composite material. The BAPPO was characterized by IR and NMR. Determine the optimal concentration of sizing agent by SEM、IFSS and monofilament stretching method. It can be found that when the concentration of sizing agent is 1%, the fiber has the best overall performance, has bundling properties, the optimal surface morphology, best interfacial shear strength and the highest monofilament tensile strength, reaching 88.63 MPa, 3.31 GPa, respectively improved by 19.67% and 3.54%, the surface energy reached 55.02 m N/m, increased 43.35% over untreated fibers.When study grafting method modified the interfacial properties of carbon fiber composite material, using XPS, SEM and other testing methods to determine the best reaction concentration. It is found that, when the BAPPO concentration, the content of P reached 3.23%, reach the highest graft rate and the Interfacial shear strength increased 17.73%, the surface energy improved 17.14%.The tensile strength decreased by 5.79%. Study secondary graft POSS on the carbon fiber surface, it is found that when POSS concentration was 1%, the reaction time was 24 h, the Si content of the grafting reaction reached a maximum of 11.37%, Si / C ratio is max, interfacial shear strength increased 15.84% and the surface energy increase 21.76%. After simulated space atomic oxygen exposure test and analysis by interfacial shear strength derived from the structure, it can be concluded that the IFSS of desized fiber, as-received fiber, sizing modified fiber, graft modified fiber and secondary graft POSS modified fiber, fell 16.65%, 13.33%, 5.22%, 1.63% and 3.95%, respectively. IFSS of desized fiber decline most, than is T300 as-received fiber, 1% sizing fiber, secondary graft POSS modified fiber, graft BAPPO fiber, respectively.Tensile strength after comparision can be found,precursor of carbon fiber extraction of carbon fiber,sizing of carbon fiber decline in the proportion of trun small,fiber tensile properties of grafted BAPPO and graft POSS has not changed.Characterize the mechanism of protection three different methods modified carbon fiber through atomic oxygen treatment by SEM、AFM and XPS. The fiber surface morphology was observed by SEM and AFM. It found that after sizing、grafting PAPPO and secondary graft POSS methods can form irregularities thickness film on the fiber surface. Analysis by XPS can obtained that grafting PAPPO and sizing fiber form PO membrane which has similar structure with phospholipid as a protective layer after AO exposure. Secondary graft POSS modified fiber form oxides of silicon and oxides of phosphorus as a protective layer to protect the fiber interface after AO exposure.