Fabrication And Study Of Carbon Fabric Reinforced Polyetherimide Matrix Composites

Owing to low density, high specific strength and modulus, corrosion resistance,fatigue resistance and other advantages, fiber reinforced resin matrix composite hasbeen widely used in the fields of aerospace, automobile, shipbuilding and sportsgoods and so on. With the development of aerospace technology, the servicetemperature of traditional epoxy and bismaleimide composites are unable to meet theuse requirements because the better performance of advanced composite is required.Owing to excellent heat resistance, chemical resistance, radiation resistance and goodcomprehensive mechanical properties, polyimide resin can be used as matrix for thepreparation of high performance composite materials used in high temperatureconditions(>300oC). Because the traditional polyimide is usually insoluble andrefractory, the matrices in the polyimide composite application are mainlythermosetting polyimide resin at present. But it has the common disadvantage ofthermosetting resin matrix composite, viz. poor impact resistance performancerelative to thermoplastic resin matrix composite, which lead to the relatively lowcompression strength after impact (CAI) and the poor failure safety performance ofcomposite materials in aerospace applications. Therefore, considering the heatresistance and impact resistance, the research and application of thermoplasticpolyimide resin matrix composites were widely carried out.In this paper, polyetherimide (PEI) was selected as resin matrix of the compositebecause of its good heat resistance and melt process capability. We hope to simply prepare composite laminates based on polyetherimide resin films and carbon fabricsby hot press molding at low cost relatively. By changing the carbon fabric type,treatment way of carbon fabric surface and resin film thickness, the effects of theseconditions on the properties of composite laminates were studied using theinterlaminar shear strength (ILSS), DSC, DMA test respectively. In addition,composite laminates were conditioned by hygrothermal aging and drying afterhygrothermal aging. The water absorption rate, and the change of ILSSs and storagemoduli for composite laminates before and after aging were evaluated.The experimental results indicated that nitric acid treatment of carbon fabric,increase of PEI film thickness and the use of4Harness Satin (4HS) carbon fabricwere conducive to increase of ILSS values for composite laminates prepared by “filmmethod” relatively. ILSS values of laminate L8N4K and laminate L8P prepared byPEI prepregs were almost the same, and they were the highest in all preparedlaminates, about80Mpa. DSC results confirmed that residual internal stress can beformed in composite laminates after molding. The thermal properties of all preparedcomposite laminates by DSC and DMA were not the same because of differentpreparation conditions. The resistance to water of laminate prepared by thin PEIfilms (30μm thickness) was poor and the water absorption rate was more than1%after hygrothermal aging. The ILSS value of laminate after hygrothermal aging werelower than that of the corresponding laminate without aging. However, the order ofILSS values of all laminates after and before hygrothermal aging was almost the same.The ILSS of Laminate L8P was still highest (70.6MPa), and the ILSS values oflaminate L8N4K and L8A4K were also high and were65.4MPa and50.9MPa,respectively. Compared with the laminate without aging, the storage modulus and Tgof the laminate after hygrothermal aging and drying after hygrothermal aging changedto varying degrees. The storage modulus curves of nitric acid treated fabricsreinforced composite laminate L8N4K and L8N5K after hygrothermal aging had“Double Glass Transition” exceptive phenomenon, but the phenomenon wasdisappeared after drying24h at100oC. Finally, through the experimental study and considering the suitable processingconditions, we determined the optimum conditions for fabricating the laminatepossessing good comprehensive performance with high interlaminar shear strengthand glass transition temperature, better resistance to moisture, viz.50μm thickpolyetherimide films and acetone treated4HS carbon fabrics, the designation ofprepared composite laminate was L8A4K.