Fiber reinforced sandwich structure with hollow core made by vacuum-assisted impregnation, e.g. for aircraft use, includes a separation layer to control resin penetration

摘要

Initially the dry reinforcing fibers a laid on one side of a hollow core, e.g. a honeycomb structure, and covered with a separating and bonding film (TV film) of a thermosetting resin (H1). The assembly is placed in a mold and covered by a second structure. The mold is then closed, evacuated and a second thermosetting resin (H2), which hardens at a lower temperature than the first resin (H1), is injected. The resins are then hardened successively at increasing temperature levels. Optionally the first film (H1) can be at least partially hardened before the assembly is placed in the mold. Independent claims are included for the following: (1) A thermosetting separating and bonding film (TV film) of a resin (H1) which is rigid enough to form a seal and has a higher setting temperature than the other resin (H2) and but is able to combine with it; (2) An intermediate product consisting of a fiber reinforced core covered with a TV film; (3) A set of resins (H1, H2) with the required properties, e.g. with a hardening temperature difference between 25 and 150 [deg]C.