Fibre is chopped in a hand-held gun and fed into a spray of catalyzed resin directed at the mould. The deposited materials are left to cure under standard atmospheric conditions. The fabrication method is depicted in Figure 1.16.
The polyester resins can be used with glass rovings is best suited for this process.
Figure 1.16: Wet or hand lay-up fabrication
Advantages:
The spray-up process offers the following advantages:
It is suitable for small to medium-volume parts.
It is a very economical process for making small to large parts.
It utilizes low-cost tooling as well as low-cost material systems.
Limitations:
The following are some of the limitations of the spray-up process:
It is not suitable for making parts that have high structural requirements.
It is difficult to control the fiber volume fraction as well as the thickness. These parameters highly depend on operator skill.
Because of its open mold nature, styrene emission is a concern.
The process offers a good surface finish on one side and a rough surface finish on the other side.
The process is not suitable for parts where dimensional accuracy and process repeatability are prime concerns. The spray-up process does not provide a good surface finish or dimensional control on both or all the sides of the product.
Cores, when needed, have to be inserted manually.
Only short fibres can be used in this process.
Since, pressurized resin is used the laminates tend to be very resin-rich.
Similar to wet/hand lay-up process, the resins need to be of low viscosity so that it can be sprayed.
Applications:
Simple enclosures, lightly loaded structural panels, e.g. caravan bodies, truck fairings, bathtubs, shower trays, some small dinghies.
