Corvus-Aircraft Ltd. develops new technologies and produces heavily used polymer equipment. These so called composite materials include: fiber-reinforced resin matrix laminates, foams, metal, polymer, and ceramic based honeycombs, and other components made from the mixture of the materials above.
The used composites involve glass, coal or aramid enhanced fibers (previously defined by the manufacturer) impregnated prepregs fabrics, ribbons, dry fabrics, ribbons, rovings, and epoxy resins for their hand wetting.The cores of the shells are PVC foams, aramid and aluminum honeycomb plates or industrial ceramic sheets.
The final product is made at high temperatures in laminating tools, under vacuum or over pressurized conditions. The machining tools are made of composite materials, produced with similar technologies as other equipment. Occasionally, pitted metal tools are also used.
The order of the composite production follows as:
-Preparation includes the materials and manufacturing aids in the preparation of specific instructions, the hand or machine cutting of pieces of specific size, and the cleaning of metal parts made for the equipment. Cleaning, cutting and vacuuming of tools are also within the scope of preparation.
-Lamination. During lamination, the specifically prefabricated material (flat patters in metal or wood paneling) is positioned in the correct location of the tool. To avoid air bubbles and puckers, the individual layers are laid on each other using hand rollers. The shells are produced by placing the core material in the front, and the outer layers wrapped around using the same exact technology as for the front laminate.
- Vacuuming. The individual layers, core materials are held together and fixed to the tool by the vacuum pressure.To create vacuum the tool is placed in a vacuum film bag, or the tool and the laminating layer is covered by vacuum film. For better efficiency, before the vacuuming process begins, the laminated layer is covered by a removing or pitted film, and a breathing paper layer which provides ventilation and the absorption of crushed matrix material. The vacuum finishing foil is closed by a tape at the edge of the tool, dedicated for this purpose.
- Heat treatment. For the full polymerization of the matrix, a desired temperature of 130-180 °C is necessary. The required heat treatment is done is cycles in computer controlled furnaces. The individual cycles are registered and evaluated after the process. Throughout the heat treatment the part inside the tool is under vacuum condition.
-Autoclave cycle. If technology requires, a special type of heat treatment is used, called autoclave cycle. The autoclave furnace is pressurized (8-10 Bar) besides maintaining the previously mentioned temperatures. Similarly to the normal heat treatment, the tools and laminating components are placed in a vacuum bag. The higher pressure provides greater press force and results in a better quality mixture of stock. All parameters of the autoclave cycle (pressure, temperature, vacuum value) are computer controlled and registered.
-Adhesives. The laminates made in several tools and veneers are glued together with the assembly of individual parts. In the case of products, made of glued laminate layers, the laminates contain adhesives, which fit another laminate during the assembly. Other structural elements which serve to strengthen and stable shapes (e.g. ribs, beams, frames) are also built in during the adhesive phase. The applied adhesives are liquids, different viscosity adhesive resins, which require high temperatures for polymerization and additional heat treatment.The adhesive is put on the surfaces using brushes and taping knives. The process takes place in a ventilated machine shop, used for this purpose.
-Finishing process. The heat treated, glued products are cooled, removed from the tool, and then trimmed ready by hand or machines. The cutting and polishing works are done in a designated workshop equipped with a dust extraction and separation unit.
