Introduction:

In this lecture we will see some of the important fabrication processes of composites. Further, we will see their advantages, disadvantages and applications.

What are the fabrication processes of composites materials? Describe the processes in brief along with the materials used in the process, their advantages, disadvantages and applications.

The fabrication processes are described in the following along with their advantages, disadvantages and applications in the following.

1. Wet/Hand Lay-Up:

The fibres are first put in place in the mould. The fibres can be in the form of woven, knitted, stitched or bonded fabrics. Then the resin is impregnated. The impregnation of resin is done by using rollers, brushes or a nip-roller type impregnator. The impregnation helps in forcing the resin inside the fabric. The laminates fabricated by this process are then cured under standard atmospheric conditions. The wet/hand lay-up process is depicted in Figure 1.15.

The materials that can be used have, in general, no restrictions. One can use combination of resins like epoxy, polyester, vinylester, phenolic and any fibre material.

Advantages:

• The process results in low cost tooling with the use of room-temperature cure resins.
• The process is simple to use.
• Any combination of fibres and matrix materials are used.
• Higher fibre contents and longer fibres as compared to other processes.

Disadvantages:

• Since the process is worked by hands, there are safety and hazard considerations.
• The resin needs to be less viscous so that it can be easily worked by hands.
• The quality of the final product is highly skill dependent of the labours.
• Uniform distribution of resin inside the fabric is not possible. It leads to voids in the laminates.
• Possibility of diluting the contents.

Applications:
The process is suitable for the fabrication of wind-turbine blades, boats and architectural mouldings.

Figure 1.15: Wet or hand lay-up fabrication