F4E Procurement of the pre-compression rings made of pultruded composite material

The highly innovative process, proposed by CNIM and chosen by F4E, is based on a pultrusion technique that involves the manufacture of profiles of epoxy S2-glass. Each pre-compression ring (PCR) is manufactured by winding the flat pultruded profile (2 mm thick and about 2800 m long) and utilizing an adhesive tape (0.12 mm thick) between layers to freeze the geometry. After the curing cycle, the PCR is machined to reach the required geometry tolerances. Each PCR will have a diameter of approximately 5 m, a cross-section of 332 mm × 288 mm and will weigh approximately 3 tons. The PCRs will finally be proof tested at 600 MPa in hoop stress that corresponds to 1.5 time the operational hoop stress. An extensive qualification phase has been released to prove that both materials and manufacturing technology can procure PCRs according to requirements. This paper describes the manufacturing processes, the results of the qualification phase and the status of the production.