Karbon Elyaf Dolgulu Polieterimid Kompozitlerin Üretimi ve Karakterizasyonu

Abstract

This study was financially supported by Hacettepe University Scientific Research Projects Coordination Unit with a graduate project entitled “Production and Characterization of Carbon Fiber Reinforced Polyetherimide Composites” (FYL-2019-18024). The aim of this study is to develop and characterize carbon fiber filled polyetherimide (PEI) composite materials with high thermal and mechanical properties, which can be recycled and used in industries such as aerospace and defence. PEI resin is a thermoplastic polymer which has high thermal stability and good mechanical properties. Therefore, PEI resin was used as the matrix element of the composite materials developed here. The effect of fiber/resin ratio and carbon fiber woven type on the thermal and mechanical properties of composite materials was investigated. For this purpose, four different composite materials with resin/fiber ratio by weight 60/40 and 40/60 and using unidirectional (UD) carbon fiber and Twill carbon fiber were produced by hand lay-up method. Composite materials, PEI resin and carbon fibers are characterized by thermal and mechanical analyses. As a result of thermal analysis, it has been determined that the thermal stability of composite materials is independent of carbon fibers and only depends on PEI resin. Therefore thermal aging study has been carried out with PEI resin and it has been obtained that the resin does not lose any mass in 10 years under isothermal conditions at 25°C, and loses 2,965x10-8 % mass after 10 years at 100°C isothermal temperature. The results showed that, the thermal service lifetimes of PEI resin and composite materials are very high. It was also determined that the structure of PEI resin and composite materials did not decompose up to 500°C and did not soften up to 200°C. The mechanical properties of the materials were characterized by dynamic mechanical analysis (DMA) and tensile test. Tensile strength, Young’s modulus and % elongation values of composite materials were obtained by tensile test. It has been determined that the tensile strength and Young’s modulus of UD carbon fiber filled composite materials are 3 times more than Twill carbon fiber filled composite materials. Viscoelastic properties of materials were determined with DMA. It has been observed that storage and loss modules of UD carbon fiber filled composite materials and composite materials with high resin ratio are higher than that of others. The mechanical service lifetime of the materials under 10 MPa load at 100°C was analyzed with DMA. Although the test conditions are very tough; it has been observed that only 30-50% of mechanical properties of composite materials are lost. As a result, it was determined that the thermal and mechanical service lifetimes of the composite materials are very high. It has been detected that the thermal properties of composite materials depend on the PEI resin and the thermal properties are independent of the carbon fiber woven type and resin ratio. It was obtained that the mechanical properties depend on the carbon fiber woven type and the ratio of resin by weight. It was determined that the mechanical properties of composite materials produced with UD carbon fiber were better than the mechanical properties of composite materials produced with Twill carbon fiber. The increase in resin ratio in weight caused decrease in the tensile strength values of the materials and increase in their viscoelastic properties.