Ultra High Temperature Composites for Service Temperature of 250°C to 320°C.
Advanced composites materials have become the front-runners in the aerospace industry. These materials have been extensively used in primary structures of recent civil aircrafts like Boeing 787, A350 XWB and Airbus 380. Majority of these structures are manufactured using carbon /epoxy prepreg systems catering to service temperatures less than 150°C. Thermoplastic composites, though processed at high temperature (≥350°C), are not suitable for higher use temperatures because of their lower glass transition temperatures.
Thermoset resins like PMR-15 are developed nearly three back for military and aerospace research projects to handle moderate-to-high temperatures and tough conditions. However, PMR-15 has a high melt viscosity that limits processability and consequently end-use. Prepreg manufacturers have developed high-temperature, structural thermosetting polyimide with a low-melt viscosity. These materials display exceptional hot/wet mechanical properties suitable for 290°C-320°C service temperature applications. These polyimide prepregs have been designed specifically to address the shortcomings of the previous generation polyimides such as marginal hot/wet performance at elevated temperatures and processing limitations due to intrinsic matrix chemistry. The new generation polyimide prepregs can be processed easily because of lower melt viscosity resulting in lower manufacturing costs and faster processing times.
ACD has made a foray into developing the technology for processing these new polyimide prepregs. Laminates of thicknesses ranging from 2mm to 5mm are successfully manufactured. Figure below shows the cured laminate along with ultrasonic C-scan image which vindicates the process adopted. These laminates are cured at 371⁰C and 12 bar pressure and autoclave is operating nearly at its design capacity. This is a very harsh environment in which proper choice of consumables for processing becomes important. Moreover, maintaining the autoclave to operate in this environment is also a demanding task.
Processed laminate along with Ultrasound C-scan image
This process will be used for development of Bypass duct assembly for Kaveri Engine.