In-situ consolidation of thermoplastic thick rings

Advanced flywheel systems are now possible with the advent of high modulus, high strength graphite composites. Most experimental composite rotors are presently filament wound using thermosets and various fibers. Tangentially wound graphite/epoxy systems generally lose effective modulus of elasticity during the autoclave process, due to relaxation of the structure. In thick sections, tooling cannot prevent this effect. Through the use of thermoplastic composites and special equipment and processes, high quality thick rings can be made without loss of fiber alignment. Using conduction in-situ consolidation of polyetherimide/IM7 tape, tangentially wound, thick rings were fabricated and nondestructively evaluated. Process parameters were successfully manipulated to avoid microcracking, to enhance fiber straightness and alignment, and to control residual stresses. This material/process/machine sets the stage for low cost production of flywheel rotors that offer the highest possible structural qualities.