CF/Soluble Poly (Aryl Ether)s Composite: Preparation, Interfacial Property And Simulation Of Thermal Stress

Poly (phthalazinone ether sulfone ketone) (PPESK) is a kind of novel thermoplastic with excellent thermal resistance and solubility. Compared with traditional thermoplastic such as PEEK, PES, PEI, the thermal resistance is increased, besides the processing property is also improved significantly. It is suitable for preparing fiber/PPESK composite by using solution impregnation technique. In our experiment, CF/PPESK composite manufacture technique was studied, CF surface modification for improving composite interfacial adhesion was carried out and composite thermal stress distribution in the outer space was analyzed.In our experiment, suitable solution for PPESK matrix was chosen by comparing the solubility of PPESK matrix in different solvents, and continuous fiber reinforced PPESK composite was prepared by using solution impregnated and compression modeling technique. Numeral analysis for non-equilibrium temperature field during compress modeling process was carried out by using intimate contacting model and energy transfer equation. The relation between the modeling temperature, pressure and modeling time were studied under non-equilibrium temperature field. A viscous-elastic finite element model was adopted to analysis the thermal stress distribution in CF/PPESK composite, and the influence of composite cooling rate on composite thermal stress distribution was discussed. At last, the processing parameters of CF/PPESK composite were optimized, and the optimal composite processing parameters were concluded.Air plasma was employed to modified CF surface, for improving the interfacial adhesion between CF and PPESK matrix. Plasma treated CF surface chemical composition was characterized by X-ray photoeletron spectroscopy (XPS). Fiber wettability was analyzed by dynamic contact angle analysis system. CF surface topography was indicated by atomic force microscopy (AFM). Composite failure mechanism was analyzed by scanning electron microscopy, and composite interfacial adhesion mechanism was also studied. Results indicate that air plasma treatment is capable of introducing -C-O-, -C-N-, -C=O as well as -COO- groups onto CF surface. Fiber surface polarity is increased. Besides, air plasma treatment can change carbon fiber surface roughness significantly. After plasma treatment, substantial amount of deep grooves can be found on CF surface. Due to plasma treatment increase CF surface polarity, fiber wettability and fiber surface roughness, composite interlamine shear strength (ILSS) is improved. After plasma treatment, composite ILSS is high up to 79.5MPa, the ILSS is increased by 13.5% compared with that of untreated CF/PPESK composite. Study of composite interfacial adhesion mechanism indicated that both chemical bonding and mechanical bonding interaction have a positive effect on composite interfacial adhesion, however mechanical bonding interaction has a dominant effect than chemical bonding interaction.As structure composite of the space craft, during the long-term serving in the orbit, the space craft travels in and out of the earth shadow area. The temperature on the surface of the space craft varies from -160℃to 120℃. Due to the coefficient of thermal expansion of the fiber and the matrix is quite different, thermal stress is caused when temperature changes. In this paper, finite element analysis method was applied to analyze the thermal stress in CF/PPESK composite, and the thermal stress of CF/PPESK composite was compared with that of CF/EP and CF/BMI composite. Results indicate that, in alternating temperature environment, thermal stress is aroused in CF/plastic composite. Composite interfacial defect zone is the weak point in CF/plastic composite. Thermal stress concentration is located in the defect zone. However, the thermal stress in CF/PPESK composite is lower than that of CF/EP and CF/BMI composite.The Parabolic failure criterion analysis implies that thermal stress has a dominant influence on CF/EP composite and CF/BMI composite, in the alternating temperature environment, thermal stress of composite defect zone will induce the matrix failure, while the influence of alternating temperature on CF/PPESK composite is relatively smaller. Thermal stress of the defect zone can not induce the matrix failure. CF/PPESK composite has a higher stability.