Vacuum bagging is a very flexible process for consolidating fibre-reinforced polymer laminates of a wide range of shapes and sizes.
The composite to be consolidated (e.g. a prepreg or hand lay-up) is placed on a single-sided mould. The material is then covered with an impervious film (the “vacuum bag”), which is sealed around the edge of the part. By evacuating the air between the mould and the vacuum bag using a vacuum pump, the part is consolidated under atmospheric pressure. The process is often performed in an oven to assist with the curing of the resin. Because the vacuum bag material can be readily cut to size, it is a very flexible process in terms of the dimensions of the parts that can be consolidated.
The material to be consolidated is placed on the open mould tool 1. It is then covered with a peel ply (a synthetic fabric with a fine weave that assists with demoulding and surface finish – it is literally peeled-off the part after moulding) and a breather fabric (a relatively thick non-woven fabric that provides an escape path for the evacuating air and which also absorbs any excess resin that bleeds out of the composite) 2. This entire lay-up is then covered with a vacuum bag and sealed around the edges, apart from the connection to the vacuum pump 3. Activating the pump sucks all the air out of the space between the vacuum bag and the mould, causing the composite to be consolidated under 1 bar of pressure 4. This will often be done in an oven to assist with the curing of the resin. Once the part is fully cured, the vacuum pump can be disconnected, the vacuum bag, breather fabric and peel ply removed and discarded, and the part removed from the mould.
The vacuum bagging process has the following strengths and limitations:
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