What is the difference between the hand lay-up and spray-up methods of composites manufacturing?
The spray lay-up technique is faster than hand lay-up, but produces a less uniform product. It consists of feeding a stream of chopped fibers into a spray of liquid resin in a mold cavity. The direction of the fibers is random, as opposed to the mats or woven fabrics that can be used in hand lay-up.
What is lay-up in composites?
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.
What is Handlay process?
1 Hand lay-up. Hand lay-up is the simplest and oldest open molding method for fabricating composites. At first, dry fibers in the form of woven, knitted, stitched, or bond fabrics are manually placed in the mold, and a brush is used to apply the resin matrix on the reinforcing material.
What is the process of composite materials?
Composite materials are formed by combining two or more materials that have quite different properties. The different materials work together to give the composite unique properties, but within the composite you can easily tell the different materials apart – they do not dissolve or blend into each other.
What is spray-up technique?
Spray-up is an open-moulding composites fabrication process where resin and reinforcements are sprayed onto a reusable mould. The resin and glass may be applied separately or simultaneously “chopped” in a combined stream from a chopper gun. The part is then cured, cooled, and removed from the mould.
What are the advantages of spray-up method over hand lay-up method?
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.
What is the difference between dry lay up and wet lay up?
The short-term is a wet layup and consists of leaving the boiler filled with concentrated, chemically treated boiler water; preferably with a pH of 12.4 (or as close as possible). The long term is a dry layup. The boiler should first be drained of all water contents within the boiler.
What is vacuum lay-up?
Vacuum bagging (or vacuum bag laminating) is a clamping method that uses atmospheric pressure to hold the adhesive or resin-coated components of a lamination in place until the adhesive cures.
How can composite materials help to protect the environment?
The use of composite materials is rapidly entering into the automotive industry thanks to a technique developed by the EPFL spin-off EELCEE. This technique promises lighter cars that burn less fuel and, consequently, emit less CO2.
What is the need for composite material?
Why Use Composites? The primary reason composite materials are chosen for components is because of weight saving for its relative stiffness and strength. For example, carbon-fibre reinforced composite can be five times stronger than 1020 grade steel while having only one fifth of the weight.
What’s the best way to make composite materials?
Due to the high demand for composite materials, there is an increase in the need for a faster production rate. Many people are replacing the lay-up process with alternative methods that encourage the automation of fabrication. Here, you should put dry reinforcement into the mold and later pump a mixture of the resin and catalyst under low pressure.
Why do resins need to be sprayable for composites?
Laminates tend to be very resin-rich and therefore excessively heavy. Only short fibres are incorporated which severely limits the mechanical properties of the laminate. Resins need to be low in viscosity to be sprayable. This generally compromises their mechanical/thermal properties.
What kind of resin is used in spray lay up?
Fibre is chopped in a hand-held gun and fed into a spray of catalysed resin directed at the mould. The deposited materials are left to cure under standard atmospheric conditions. Resins: Primarily polyester.
How is curing done in a spray up process?
After spraying fiber and resin to required thickness, curing of the product is done either at room temperature or at elevated temperature. After curing, mold is opened and the developed composite part is taken out and further processed further. The time of curing depends on type of polymer used for composite processing.