What is FRP and FRP Pultrusion?


What is FRP and FRP Pultrusion ?

Emergence of composite materials was a great development in the field of material engineering. Discovery of new type of composites led to the replacement of many traditionally used materials.

Carbon fiber based plastics, glass fiber based plastics and other materials began to be used in high end applications like space, defense, aircrafts, robotics, special structures as well as in industries like automobile etc.These materials began to replace metals and cement based structures where high strength and light weight was the defining criteria.These materials can be fabricated with specified parameters like strength, shape and size, colour, durability, UV protection, impact resistance etc.

With the emergence of newer fabrication techniques like FRP Pultrusion mass production ensuring highest quality pultruded profiles  in the factory became a reality.

 

Pultrusion Process:

FRP pultrusion profiles  are  made by caterpillar or hydraulic pultrusion machines. This pultrusion process creates continuous composite profile by pulling raw composites through a heated die.

Frp pultrusion machine

 

Pultrusion combines words “pull” and “extrusion” where extrusion is pulling of material such as fiberglass and resin,through a shaping die. The pultrusion process starts with racks or creels holding rolls of fiber roving.
Most often the reinforcement is fiberglass, but it can be carbon, aramid, or a mixture. This raw fiber is pulled off the racks and guided through a resin bath or resin impregnation system.

PulProc

Many resin types may be used in pultrusion including polyester, polyurethane and vinyl ester epoxy resins etc. Resin is mixed by resin mixer and  directly into the die in some pultrusion systems. The raw resin used is a thermosetting resin (hardens on heating), which is sometimes combined with fillers,catalysts, and pigments.

The fiber becomes fully impregnated (wetted-out) with the resin such that all the fiber filaments are thoroughly saturated with the resin mixture. Then this is passed through “preformer” which is a tooling arrangement to squeeze out extra resin and organize the fiber into correct shape. The un-cured composite material is guided through a series of tooling. This custom tooling helps arrange and organize the fiber into the correct shape. Often continuous strand materials and surface veils are added in this step to increase structure and surface finish.

Once the resin impregnated fiber is organized and removed of excess resin, the composite will pass through a heated steel die. Precisely machined and often chromed, the die is heated to a constant temperature, and may have several zones of temperature through-out its length, which will cure the thermosetting resin.

The profile that exits the die is now a cured pultruded Fiber Reinforced Polymer (FRP) composite. This FRP profile is pinched and pulled by a “gripper” system. Either caterpillar tracks or hydraulic clamps are used to pull the composite through the pultrusion die on a continuous basis. At the end of this pultrusion machine is a cut off saw. The pultruded profiles are cut to the specific length and stacked for delivery.

 

Pultruded profile’s advantage compare with other composite processing method

FRP pultruded products are often stronger then a similar product manufactured by hand-layup,vacuum bag infusion, and other composite processing methods. During the pultrusion process,the many fiber bundles are pulled downstream using hydraulic or caterpillar grippers.

Due to this pulling, the fiber filaments are in tension when curing in the heated die. When in tension, the fibers have higher strength values and are better aligned allowing good compaction, with more fibers fitting into a given volume. Fiber density is extremely high, as all excess resin is squeezed out before entering the die.

Standard pultrusions can have fiber content of 50% by volume, 70% by weight.

On 23, 7, 2014, posted in: FRP Profile News by Tags:

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