By 2024, the global market size of composites will be about $130.83 billion. The primary reinforcing material in the U.S. is glass fiber. In 2017, it recorded a growth value of $2.1 billion.
There is a growing demand for robust, durable, and lightweight materials. Many industries are turning to composites to find reinforcements of a specific design.
They want to solve the challenges that fiber-reinforced polymers face. These reinforcements are products of composite fabrication.
There are various composite fabrication methods in the industry. Your decision depends on the material, design, and the application of the composite.
Here are some of the most popular methods.
1. The Hand Lay-Up
The hand lay-up is the most basic method of fabrication used on thermoset composites. The process involves laying prepreg plies onto a tool by hand to create a laminate stack.
Once the lay-up is complete, you need to apply the resin to the layer of plies. In a different variation of the hand lay-up known as the wet lay-up, you need to coat each ply with resin before layering them together.
2. Open Molding
Contact molding or Open Molding is a low-cost process used in the creation of fiberglass composite materials. The mold is first treated with a release agent and gel before the fabrication begins.
Place the molding materials on top of the mold through either the spray up process or the hand lay-up process. In the spray-up process, you should spray the resin and chopped strands on to the molding surface simultaneously.
Then compact the laminate using hand using rollers, and add any core material at this point. A final spray up layer helps to place the core materials between the laminate. Afterward, you can allow the molding to cure.
You can sometimes use the hand lay-up process alongside the spray lay-up in a bid to reduce the labor.
3. Resin Infusion Methods
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.
These fabrication methods include:
The Resin Transfer Molding
Here, you should put dry reinforcement into the mold and later pump a mixture of the resin and catalyst under low pressure.
The resin used is of low viscosity so that it can permeate the preform before it cures. The process produces high-quality parts without the need for an autoclave.
Reaction Injection Molding
It bears a notable difference to the resin transfer molding. Instead of injecting the resin and catalyst as a mixture, you insert them in two separate streams.
The chemical reaction that occurs during the mix then takes place in the mold instead of the dispensing head.
Vacuum-Assisted Resin Transfer Molding (VARTM)
VARTM stands out from the other resin transfer molding processes since it does not need the use of heat or pressure. Rather than pumping the resin using pressure, the VARTM draws it into the preform using a vacuum.
Thus, VARTM uses low-cost tools, making it easy to produce a considerable amount of inexpensive and complex parts.
The significant advantage of the filament winding fabrication method is that its material costs are low. The process is continuous and can be highly automated.
The most significant area of application is in the making of golf club shafts.
Other items, such as cylindrical parts, fishing rods, and pressure vessels, take the remaining portion of the business.
Pultrusion method is a simple and continuous process. Here, you first pass the reinforcing fiber through a hot bath of resin. It is then designed to specific shapes as it goes through several forming guides.
Afterward, it passes via a heated die before it assimilates to its final shape and cures. The products made through pultrusion are smooth and do not need post-processing.
The method has been in use for decades in the making of glass fibers and polyester resins.
Tube rolling is a fabrication method that you can use in the making of rods and tubes. Its main products are tapered or cylindrical tubes with a small diameter.
In this process, you should first pre-cut the material into patterns that will help with the fiber architecture. They are then laid out on a surface where a mandrel roll over them to compact and debulk the materials.
You should reposition the pattern pieces at regular intervals so that you can give the tube bending strength.
This method is useful in the processing of high-volume thermosets. It is the best option to use when you have to produce more than 10,000 parts.
Composite sheet materials are made using a sheet making compound. You should first place a resin-paste down and pour chopped fiberglass on top. Then you can cover the fiberglass using a final layer of resin paste.
The auto industry is exploring the use of sheet molding compounds that have a carbon reinforcement. It is in a bid to take advantage of the strength and stiffness to weight ratio of carbon.
It is a fast and low-pressure method common in the fabrication of filled thermoplastics. The process is quick, with injection speeds between one to five seconds. One hour is enough to produce as many as 2000 small parts.
Automated injection molding of BMC is rising in the ranks and taking over some of the markets held by metal castings and thermoplastic manufacturers.
Important Details to Note When using Composite Fabrication Methods
Composite materials carry many desirable properties that make them suitable for use in various applications.
The composite fabrication methods listed above help to shape resins and reinforcements, giving the composite material its desired shape.
When handling composite materials, it is imperative for fabricators to maintain a safe working environment. They should also address the health and safety concerns by using protective gear and developing company-wide monitoring policies.
Contact us today for more information on the use of composite materials.