Glass Fiber Reinforced Plastic

A composite material made of resin as matrix and glass fiber as reinforcement. It can significantly improve the strength, heat resistance, and creep resistance of plastics.

The common forms of glass fiber include long fiber, short fiber, glass cloth, glass fiber mat, etc. Generally, glass fiber needs to work with coupling agent to enhance its interfacial adhesion with resin.

Glass fiber reinforced plastic could be divided into two categories: glass fiber reinforced thermoplastics, such as glass fiber reinforced polypropylene, nylon, polyester, etc; Glass fiber reinforced thermosetting plastics, such as glass fiber reinforced unsaturated polyester, epoxy resin, phenolic resin, etc.

glass fiber

The advantages of glass fiber reinforced plastic are that the material has light weight, high strength, good corrosion resistance, good thermal and electric insulation, high transmittance and low cost.

The disadvantages are low modulus (Modulus is a physical quantity that describes the resistance of solid materials to deformation)and poor long-term temperature resistance.

Glass fiber reinforced plastic is widely used in machinery manufacturing, petrochemical industry, transportation, aerospace, construction and other industrial fields.

My understanding of the structure of GFRP:

Glass is a kind of brittle material with low strength, but its properties could change after it gets melted and stretched into fine glass fiber.
This kind of glass fiber is very thin but containing high strength. It can even be woven into cloth.

FRP is like reinforced concrete: glass fiber is the hard steel bars in concrete while resin is the adhesive cement. The combination of glass fiber and resin not only has the composition of glass but also has the strength of steel.

gfrp furniture
gfrp furniture

The manufacturing process of Glass Fiber reinforced plastic:

  1. mold cleaning: clean the mold and wipe it with soft cloth. There shall be no impurities on the surface.
  2. Apply release agent: the release agent must be applied evenly. Polyvinyl alcohol needs to be completely dry. other release agents such as polishing wax and non-silicon oil paste need to wait for two hours to volatilize the solvent.
  3. Apply gelcoat resin: gelcoat ingredients shall be fully mixed, especially when fillers and pigments are used for the product. Uneven mixing will leave spots or marks on the surface of the product and affect its appearance. The thickness of the gelcoat shall be controlled accurately. The gelcoat can be applied when it is sticky but does not leave on the finger.
  4. Cutting glass fabric: calculate the required layers of glass fabric according to the size and thickness of the section. The size of the glass fabric shall be slightly larger than the mold.
  5. Glue preparation: select the type and proportion of curing agent and accelerator according to the required gelation time and environmental conditions. A small amount of color paste can be added when the product is in color.
  6. Pasting: Brush a thick layer of resin on the gel coat layer as evenly as possible, and then the first layer of glass reinforcement shall be pasted. After the glass fabric is completely soaked, apply another layer of resin and repeat the process until it reaches to the required thickness.
  7. Room temperature curing: after the sections are pasted, they need to stay in the mold for more than 24 hours to complete the curing.
  8. De-moulding
  9. Trim the rough edge
  10. Edge sealing: glass fiber is not water-resistant. The cut edge of FRP products is easy to cause delamination and affect the quality of products due to the exposed fibers.
  11. (the de-moulded sections must be waited for more than one week to ensure it is completely cured).
  12. Painting: all marks on FRP products shall be washed off before painting. Low-temperature paint shall be used, and the drying temperature of the paint shall not exceed 80 ℃.


  1. Author: Xia Zhengnong, Chen Zhili. 《Da Ci Hai: materials and science volume》, published by Shanghai Dictionary Publishing House on December, 2015. 
  2. “The most detailed introduction of FRP production process.” Official website of Shenzhen Yilian FRP Products Co., Ltd.

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