page_title: Lay-Up process
section_title: Polymerization in autoclave and industrial oven
hierarchical_section_title: Lay-Up process / Polymerization / Polymerization in autoclave and industrial oven
caption_attribution_description: Italiano: Autoclave Persico Marine
context_page_description: A Lay-Up process is a moulding process for composite materials, in which the final product is obtained by overlapping a specific number of different layers, usually made of continuous polymeric or ceramic fibres and a thermoset polymeric liquid matrix. It can be divided into Dry Lay-up and Wet Lay-Up, depending on whether the layers are pre-impregnated or not.
  Dry Lay-up is a common process in the aerospace industry, due to the possibility of obtaining complex shapes with good mechanical properties, characteristics required in this field. On the contrary, as Wet Lay-Up does not allow uni-directional fabrics, which have better mechanical properties, it is mainly adopted for all the other areas, which in general have lower requirements in terms of performances.
  The main stages of the Lay-Up process are the cutting, the lamination and the polymerization. Even if some of the production steps can be automatised, this process is mainly manual, leading to laminates with high production costs and low production rates with respect to the other techniques. Hence, nowadays, it is mainly suitable for small series productions of 10 to 1000 parts.
context_section_description: This process can be done at room temperature with just a vacuum pump, to control vacuum, with the aid of an industrial oven connected to a vacuum pump, to control temperature and vacuum, or with an autoclave, to control temperature, vacuum and also hydrostatic pressure.
  Polymerization in the autoclave is a technique which allows obtaining laminates with the best mechanical properties, but it is the most expensive and it permits the use of open moulds only. The advantage is due to the fact that the pressure helps to bond the composite layers and to exhaust air inclusions and volatile products, increasing the quality of the process. Each combination of fabric and resin has its own optimal polymerization cycles, dependent on fibres wettability and resin properties, like viscosity and gel point. Typically, the three cycles of temperature, pressure and vacuum are experimentally studied to obtain the best combination of the three parameters. Polymerization in the industrial oven is similar but without pressure control. It is less expensive and therefore used for all those laminates which do not need to have very high mechanical properties. Moreover, as industrial ovens, in general, are bigger than autoclaves, they are used for all those components with non-standard dimensions.
caption: Persico Marine's autoclave.
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