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Detailed explanation of composite molding process
 June 20, 2022
 
The composites industry makes a huge contribution to the economies of various countries. It's an industry, it's an economic force, it's the fuel of the economy. It is impossible for anyone to understand this industry without at least understanding the manufacturing process of composite materials. It is right to understand the situation of the composites industry by looking at its main processes.

This article will give you extensive knowledge about this. There are three manufacturing processes for fiberglass composite materials. Includes polymer molding, closed molding, and open molding. Within these molding categories, there are various processing methods with advantages. Let's look at all of them for a better understanding.
 
Three manufacturing processes for composite materials:
1. Filament winding moulding
During the fiber winding molding process is one of the primary processes when the manufacturing of resin matrix composite materials. Under the condition of controlling tension and predetermining wire style, the continuous roving or cloth be impregnated with resin liquid and twined continuously on the core mould or the liner of product cavity. Then products shall be cured in green house or under heating condition to form certain shape.


Related product: fiberglass direct roving
2. Pultrusion
Pultrusion is a manufacturing process for producing continuous lengths of reinforced polymer structural shapes with constant cross-sections. Raw materials are a liquid resin mixture (containing resin, fillers and specialized additives) and flexible textile reinforcing fibers. The process involves pulling these raw materials (rather than pushing, as is the case in extrusion) through a heated steel forming die using a continuous pulling device.
The reinforcement materials are in continuous forms such as rolls of fiberglass mat and doffs of fiberglass roving. As the reinforcements are saturated with the resin mixture (“wet-out”) in the resin bath and pulled through the die, the gelation, or hardening, of the resin is initiated by the heat from the die and a rigid, cured profile is formed that corresponds to the shape of the die.

Related product: glass fiber direct roving
3. Spray-up molding
When spray-up molding process is employed, spraying equipment shall be used to atomize the resin, and after the atomized resin is mixed with the instantly cut fiber in the air and lands on the mould surface, the air bubble shall be compacted and eliminated. Spray moulding can also be regarded as curing moulding. Spray moulding develops on the basis of manual moulding and the fiber application and resin impregnation in manual process are now can be finished by equipment, which is a relatively high-efficiency moulding process.


Related products: fiberglass gun roving
4. Hand lay-up
Hand lay-up is an open forming method for the manufacture of composite materials. It is the simplest and oldest method and can be considered within the lamination methods suited especially for large components. A reinforcing material such as glass, polymeric or carbon fibers are placed manually into the open mold after having poured a resin which, in this case, may be a suspension of geopolymer. Manually, using a trowel or roller, the suspension is spread all over the mold, soaking the fibers. The hardening step follows before demolding.
 
Related products: woven fabric, surfacing mat and chopped mat
5. Compression Molding
Compression molding process is a mass production method where resin, additives and fiberglass reinforcenments are mixed & heated to reach a certain vicostiy,and compressed under specified temperature & pressure,and cured to form the parts.
Compression molding products include SMC(Sheet Molding Compound) and BMC(Bulk Molding Compound).
 
Sheet molding compound (SMC):
 
SMC prepregs which are resin pastes made of matrix resin (unsaturated polyster resin), filler and other auxiliary shall be prepared at first to impregnate the chopped fiberglass (cut through wire from multi-end roving and generally the length shall be 25mm), and sheet moulding compound wrapped by PE film on both sides of the glass. The quantitative and SMC moulding materials whose film is ripped off and which are cut in certain shape shall be put into the metal match moulds, and composite material products in stipulated dimension and shape shall be formed under certain temperature and pressure.
Bulk molding compound (BMC):
 
First, bulk molding compound (BMC) which is bulk impregnation material made of matrix resin (unsaturated polyster resin), filler, fiberglass chopped strand and so on shall be prepared.Then BMC shall directly be put into the metal mould to form composite material products.
 
6. Continuous Panel Molding
Continuous panel molding process is to impregnate unsaturated polyster resin with fiberglass through continuous moulding sets, and then continuous panel shall be obtained with specific cross shape through heating, moulding and curing of the template. Specifically, continuous fiberglass roving cut into fixed-length fiber through the cutter shall be scattered on resin layers (or the chopped fiber mat shall be applied on resin layer) and impregnated with gum for heating; an anti-ageing film shall be placed on the upper part so that a sandwich zone can be formed between fiberglass and resin layer of upper and lower layers. The sandwich zone can be shaped through different cross templates and placed into the curing oven for shape fixation. Then the shaped glass reinforced plastics panel shall be cut.


Compared with other panels, FRP panel has such advantages as light weight, high intensity and excellent impact resistance, especially the unique light-transmitting performance and section designability.

Related products: multi-end roving and chopped mat
7. Injection molding
Injection molding is also called infusion moulding. During injection moulding, granules or powdery plastics are sent to the heated charging barrel through the hopper of injection moulding machine and become molten state through heating and fluxing, and the melted granules or powdery plastics shall be injected to the low-temperature and closed mould cavity through the nozzle at the end of the hopper under the pressure of screw. Shape given by mould cavity will be maintained after cooling and curing and then colloid can be taken from the cavity, thus a processing cycle is accomplished.

Related products: chopped strand and direct roving
8. Extrusion molding
Plastic extrusion moulding is to turn the heated or unheated granule into continuous formed products through moulding hole (neck mould)
Since extrusion moulding is widely used, can produce products continuously and is highly efficient, it plays a pivotal part in plastic processing industry and now products manufactured through extrusion moulding take up 1/3 of the total plastic products.


Related products: thermoplastic chopped strands and thermoplastic direct roving
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