High-performance polyetherimide composites
Topic(s) : Material science
Co-authors :
Diana BRATILESCU (AUSTRIA), Alexander BISMARCK (AUSTRIA)Abstract :
For a multitude of applications, especially in the aerospace sector, it is very important that composite materials do not only poses superior mechanical properties but also perform at high service temperatures.[1,2] To that end, many high-performance thermoplastics, such as poly(ether ether ketone) (PEEK), poly(ether sulphone) (PES), poly(phenylene sulphide) (PPS) have been explored as potential candidates.[2,3] Polyetherimide (PEI) represents a suitable matrix choice for composites exhibiting a high glass transition temperature (Tg ) of approximately 220 ºC at relatively low cost compared to other high-performance polymers, such as PEEK or PES.[3] Polyetherimide possesses superior mechanical properties at temperatures up to 200 °C. Producing high Tg polymer composites is challenging.[2] Here, we present a simple method to produce carbon fiber-reinforced PEI tapes and laminates containing 58 vol% carbon fibres using our purpose-build composite production line.
Carbon fibers (HexTow® AS4D, 12 k) were first spread using an air-assisted fiber tow spreading unit (Izumi International Inc, US) to increase the spacing between the filaments. The width of the carbon fibers tow increased from 5 - 7 mm to 18 – 22 mm. The spread fiber tow was impregnated with the polyetherimide by using the fibre impregnation line. The spread carbon fibres were guided into a continuous stirred aqueous resin impregnation bath containing 4.5 wt% polyetherimide, 0.45 wt% surfactant and 0.6 wt% ethanol. The wet impregnated tow was passed through two infrared (IR)-ovens operated at 380 °C in which water was removed and the polymer melted. The impregnated tape was guided to a set of three heated pins operated at 260 °C with the purpose of smoothing the surface and removing the surplus polymer. Finally, the prepreg was collected on a winder. The thermoplastic prepreg was cut and hot-pressed at 380 °C and 2 t for 60 min in a 12.5 x 2 x 0.22 cm mold.
Optical microscopy images of the manufactured prepregs and laminates showed that carbon fibres were impregnated with polyetherimide, and the polymer was homogenously distributed. The void content of the composites was determined to be between 1.4 and 2 %. The single fibre pull-out tests and the short beam shear strength showed similar values of 43 ± 0.6 MPa and 44 ± 10.1 MPa, respectively. The composites exhibit a compressive strength of 189 MPa, higher than the strength of carbon fibre-reinforced PEEK composites and a compressive modulus of 110 GPa.[4]
Carbon fibers (HexTow® AS4D, 12 k) were first spread using an air-assisted fiber tow spreading unit (Izumi International Inc, US) to increase the spacing between the filaments. The width of the carbon fibers tow increased from 5 - 7 mm to 18 – 22 mm. The spread fiber tow was impregnated with the polyetherimide by using the fibre impregnation line. The spread carbon fibres were guided into a continuous stirred aqueous resin impregnation bath containing 4.5 wt% polyetherimide, 0.45 wt% surfactant and 0.6 wt% ethanol. The wet impregnated tow was passed through two infrared (IR)-ovens operated at 380 °C in which water was removed and the polymer melted. The impregnated tape was guided to a set of three heated pins operated at 260 °C with the purpose of smoothing the surface and removing the surplus polymer. Finally, the prepreg was collected on a winder. The thermoplastic prepreg was cut and hot-pressed at 380 °C and 2 t for 60 min in a 12.5 x 2 x 0.22 cm mold.
Optical microscopy images of the manufactured prepregs and laminates showed that carbon fibres were impregnated with polyetherimide, and the polymer was homogenously distributed. The void content of the composites was determined to be between 1.4 and 2 %. The single fibre pull-out tests and the short beam shear strength showed similar values of 43 ± 0.6 MPa and 44 ± 10.1 MPa, respectively. The composites exhibit a compressive strength of 189 MPa, higher than the strength of carbon fibre-reinforced PEEK composites and a compressive modulus of 110 GPa.[4]