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LFI – The lighter, less expensive alternative to FRP

Compared to Fiberglass Reinforced Plastic, Long Fiber Injection is lower in weight and cost and provides better impact resistance.

Fiberglass Reinforced Plastic (FRP) is a composite material made of a polyester-based thermoset plastic that is reinforced with glass fiber to give it greater strength.  This combination of polyester and fiber is known to have one of the best strength-to-weight ratios in the world.  It is also extremely durable and won’t corrode, rot or dent.  It’s a material that can last for decades.

For all of its good qualities, FRP has its share of shortcomings.

The typical process used to produce FRP parts is known as hand lay-up.  And yes, the word “hand” means what you think it means — a manual, labor intensive process.  (In such a highly automated world, it’s interesting to note that there are still manufacturing processes done by hand).

To create an FRP part, only a single mold is needed; the cavity or A-side.  This mold can be made from just about anything (from plywood to steel) and, theoretically, can be as large as needed.  Once the mold has been created, a barrier coat is sprayed first to provide a clean finish.  Following that, the polyester blend and glass fiber are layered on top.  As the polyester blend begins its slow reaction cycle, it takes some manpower to roll it out and help push the material into the A-side details.  Once finished, the mold is set aside for the next few hours to allow curing.

If you have experience using FRP to make parts, you understand that the strength-to-weight ratio it provides is second to none, but also, that it is a slow, costly process that makes the most sense for lower volumes.  Furthermore, it lacks B-side details (unless you mold a second, inverse part and bond them together, which adds more cost and time) and post-paint processing is almost always required, which can add an additional 50% to the cost.

Obviously, no single manufacturing process is a one-size-fits-all solution.  A good design engineer will have vetted the available options and choose the best one for the project.

One of the more popular options that should be considered alongside FRP is a process called Long Fiber Injection (LFI).

LFI is a similar process to FRP, but it is highly automated and uses a polyurethane-based plastic instead of a polyester-based plastic.  Just like FRP, a barrier coat is first applied to provide a smooth, clean finish, but done so robotically.   Secondly, a high-gloss paint can be color-matched and sprayed directly into the mold.  Next, a mixture of polyol and iso are combined with 1” long glass fibers and robotically sprayed into the core of the mold where it is compressed with low pressure and cured within minutes, not hours.

The resulting part is a beautiful, Class A finished part with B-side details — ribs for even greater strength and bosses for mounting purposes — that is lighter, has greater impact resistance and comes in at less cost with the potential to produce higher volumes.

Choosing LFI as an alternative to FRP will result in parts that are:

  • 50% lighter
  • Nearly 100% better impact resistance
  • Lower per part cost
  • Class A finish straight out of the mold that includes B-side features

This type of technology has been perfected over the past few years and has been proven in the field to replace a wide range of FRP applications including, body panels, roofs, fenders and fascias.

Your project requirements will determine the process and material you choose for your project.  But LFI provides design engineers with a new alternative to FRP projects.

To learn more about LFI, Click here >