Fabrication Methods

Spray Layup

This method consists on projecting a mixture of resin, catalyst and pieces of short fibres on the interior face of a mould:

It is a relatively cheap method and it allows obtaining pieces from great cured dimensions at environmental temperature and atmospheric pressure.

This method, however, is not under any circumstances applicable for pieces of mechanical appointment due to the low mechanical properties of a composite formed by short fibres in random disposition and the few guarantees that offers the curate in ambient temperature without pressurizing.

Laminate by damp way

This method consists of the application of dry fabric against the surface of the mold and, later the impregnation through paint roller or brush of the resin.

Respect to the before method, it has the strong advantage of having fabrics of continuous fibres in form that the mechanical properties of the composite are very upper. Despite everything, it is difficult to guarantee the proportion between fibre and resin and it presents the same inconveniences of the curate at temperature and pressure environmental. Thus, it is considered that it is not an advisable method for pieces of mechanical appointment.

Cooking with vacuum bag

This method is a complement of the before one that consists in stamping the laminate in a bag that in to make it the vacuum, compacts the laminate against the mold:

This way it found a better compacting of the evacuating layers achieves possible bubbles of air and draining the surplus of resin fits out of the laminate. The mechanical properties of the laminate obtained are better than in the previous cases and it can be evaluated as a method to manufacture pieces of moderate mechanical appointment.

Fabric pre-impregnate (pre-pregs) cocked in autoclave

These fabrics are pre-impregnated with a pre-catalyzed resin by the manufacturer of the material. The catalyst keeps latent in form prolonged in ambient temperature providing to the material many weeks of useful life once defrosted. However, to prolong the life of storage, the materials avoid frozen to -18 ºC.

The pre-pregs take place at hand in the surface mold, where is made the vacuum and afterwards heats up to 80-150°C under an external pressure of 6 bars in an autoclave. This allows firstly at the resin to flow about the fibres and finally to take the mechanical properties.

The use of pre-impregnated fabrics reduces the costs of manipulation and allows a very good control of the volumetric proportion between fiber and mold, essential to be able to guarantee the mechanical contributions of the laminate. It is a method that offers mechanical guarantees and it is in a wide way used in applications like chassis of F1 or structural components for airplanes.

Resin transfer moulding (RTM)

This method consists on closing preforms of dry fabric into a specific mold and to inject later the resin assisting the fluency of the resin through vacuum.

The obtained parts for this procedure can guarantee a very high proportion of fiber with low contents of vacuum and allow the obtaining of pieces where all faces have one good roughness from mold. As inconveniences it is necessary to highlight that the necessary inversion is very upper to the previous methods and that the set-up of the tooling can be difficult to guarantee that zones dry or with little impregnation of resin do not exist. Also it difficult the utilization of very porous kernels or with cells like the honeycomb for the trend to fill in the cells with resin. The ideal application for this method is for pieces of small size and great complexity such like components of automotion, aeronautics or railwaymen.

Others

On the side of the presented methods, it there other of more automated but with strong restrictions regarding the form of the pieces obtained and with costs of inversion very big. Among the more distinguished, we can call the FP (Fibre Placement), the ATL (Automated Tape Location), winding filament or the pulltrusion. There are also variations of the system RTM that they pursue to simplify tooling like the RTM-Light or the infusion of resin.