Starting from the decade of the 70s, the improvement of solid rocket motors structural components has been focused on the potential use of composite materials as alternative to conventional metallic parts. Since then Avio has experienced in the field of filament winding technology, which is a manufacturing technique that enhances the unique properties of carbon fibers: strength and lightness.
Nowadays, composite cases are the baseline for future launcher development. The filament winding technology is well suited for solid rocket motors, that require higher temperature performance limits, lower void contents, increased mechanical properties and reproducibility.
The cases of the first three stages of Vega launcher (P80, Zefiro 23 and Zefiro 9) are all made by filament winding. During composite case manufacturing, a thermal protection is first applied on a metal supporting structure (mandrel) and then polymerized. Subsequently, tows of carbon fibers impregnated with resin (prepreg) are wound on the thermal protection.
After filament winding, the composite case is cured, then the mandrel is removed: the insulated motor case is obtained and is ready for propellant casting. More than 4000 km of carbon fibers are wound to produce the first three stages of Vega launcher.