Commonly Used Composites and Their Benefits for FRP, RTM, SMC, and LFI
There are a variety of common composites out there when it comes to automobiles and other forms of transportation. FRP, RTM, SMC, and LFI are some of the most notable ones. Each has its own unique set of benefits, making it relevant and valid to today’s industry needs and standards. Below is a quick glance at these composites and what each of them has to offer.
Fiber-Reinforced Plastic (FRP)
FRP is a composite substance consisting of a polymer matrix which is strengthened by fibers. These fibers can consist of a number of materials including aramid, glass, basalt, or carbon. The polymer is typically a thermosetting plastic that consists of polyurethane, vinyl ester, polyester, or epoxy.
The benefits of FRP are many. This particular composite resists corrosion since it is waterproof and nonporous. FRP has a strength to weight ratio that is higher than metals, thermoplastics, and concrete. It allows for good single surface dimensional tolerance as it’s affordably manufactured using 1 mold half. Fiber- Reinforced plastics can conduct electricity with fillers added, handles extreme heat well, and allows for many desired finishes.
Resin Transfer Molding (RTM)
RTM is another form of composite liquid molding. A catalyst or hardener is mixed with a resin and then injected into a mold. This mold contains fiberglass or other dry fibers which help to strengthen the composite.
The RTM composite allows for complex forms and shapes such as compound curves. It is lightweight and extremely durable, with fiber loading ranging from 25-50%. of RTM consists of fiber content. Compared to other composites, RTM is relatively affordable to produce. This molding allows for finished sides both outside and inside with a multi-color capability.
Sheet Molding Compound (SMC)
SMC is a ready-to-mold reinforced polyester that consists of mainly glass fiber, but other fibers can be used as well. The sheet for this composite is available in rolls, which are then cut into smaller pieces called “charges”. Longs strands of carbon or glass are spread out on a resin bath. The resin typically consists of epoxy, vinyl ester or polyester.
The main virtue of SMC is increased strength due to its long fibers, as compared with bulk molding compounds. It is corrosion resistant, affordable to produce, and is used for a variety of technology needs. SMC is utilized in electrical applications, as well as for automotive and other transit technology.
Long Fiber Injection (LFI)
LFI is a process that results from polyurethane and chopped fiber being combined and then sprayed into a mold cavity. This mold cavity can be painted as well producing a very affordable finished part right out of the mold. While it is often compared to SMC as a process technology, the major benefits are that it provides a more cost-effective solution for painted parts, along with having lower tooling costs due to its lower molding pressures. There are also a number of other crucial steps in the process of making LFI materials including metering, pouring, painting, and curing.
LFI boasts increased strength due to its long chopped fibers. This composite can be manufactured accurately, consistently, and quickly making it very affordable compared to many other composites. Composite parts manufactured with LFI technology are of lighter weight and exhibit more versatility as compared to other traditional composite processes. Although LFI has been used for a while now in vehicle and other transit manufacturing, it is beginning to gain increased respect in the housing construction market as well.
Each of the common composites featured here has their own unique advantages. Depending on the desired end results of a product, each should be carefully considered to see which one will best suit a company’s needs.
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