Glass is hard and fragile, with excellent transparency and characteristics such as high-temperature resistance and corrosion resistance; while steel is very hard and not easy to break, and also has the characteristic of being heat-resistant. Therefore, people began to imagine whether it would be possible to produce a material that possesses both the hardness, high-temperature resistance, and anti-corrosion properties of glass, as well as the tough unbreakable quality of steel. Thus, after continuous experimentation, fiberglass-reinforced plastic (FRP) was created.
**Definition of Glass Fiber Reinforced Plastic (GFRP):**
The scientific name for fiberglass is glass fiber reinforced plastic. It uses glass fibers and their products (glass cloth, tapes, mats, yarns, etc.) as reinforcing materials, and synthetic resins as matrix materials. This composite material refers to when one material cannot meet usage requirements, two or more materials are combined together to form another material that can meet people's needs—this is known as a composite material. For example, individual glass fibers, although having very high strength, are loose between fibers and can only withstand tensile stress but not bending, shear, or compressive stresses, and they cannot easily be formed into fixed geometric shapes—they remain soft. If synthetic resin is used to bond them together, various rigid products with fixed shapes can be made that can withstand both tensile and bending, compression, and shear stresses. This forms a glass fiber-reinforced plastic matrix composite material. Because its strength is equivalent to steel, and it contains glass components, it also has the color, shape, corrosion resistance, electrical insulation, and thermal insulation properties of glass. Therefore, historically, the term "fiberglass" was coined because it is easy to understand. From this, we can see that the meaning of fiberglass refers to a reinforced plastic where glass fibers serve as the reinforcing material and synthetic resin serves as the bonding agent, which is called glass fiber reinforced plastic internationally. With the development of China's fiberglass industry, the reinforcing materials for plastic-based composites have expanded from glass fibers to carbon fibers, boron fibers, aramid fibers, alumina fibers, and silicon carbide fibers. The concept of fiberglass alone cannot encompass these new high-performance fiber-reinforced composite materials. We call these fiberglass composite materials.
**Characteristics of Fiberglass (FRP):**
1. **Lightweight and High Strength:**
- Relative density ranges between 1.5 to 2.0, only 1/4 to 1/5 of that of carbon steel, yet tensile strength approaches or even exceeds that of carbon steel, and specific strength can compare with advanced alloy steels. Therefore, in applications such as aviation, rockets, spacecraft, high-pressure containers, and other products requiring weight reduction, fiberglass shows remarkable effectiveness. Some epoxy FRPs achieve tensile, flexural, and compressive strengths exceeding 400 MPa. Refer to Table 1-1 for the density, strength, and specific strength of some materials.
2. **Good Electrical Properties:**
- An excellent insulating material, used to make insulators. Maintains good dielectric properties even at high frequencies. Good microwave permeability, widely used in radar antenna covers.
3. **Good Thermal Properties:**
- Low thermal conductivity, at room temperature ranging from 1.25 to 1.67 kJ/(m·h·K), only 1/100 to 1/1000 of metals, making it an excellent thermal insulator. In cases of instantaneous ultra-high temperatures, it is an ideal thermal protection and ablation-resistant material, capable of protecting spacecraft from high-speed airflow erosion at over 2000°C.
4. **Good Corrosion Resistance:**
- FRP is a good corrosion-resistant material, resisting atmospheric conditions, water, and generally concentrated acids, alkalis, salts, and multiple oils and solvents. It has been applied in various aspects of chemical corrosion prevention, gradually replacing carbon steel, stainless steel, wood, and non-ferrous metals.
5. **Good Design Flexibility:**
- Can be flexibly designed according to needs to create various structural products, meeting usage requirements and ensuring product integrity.
- Material selection can be optimized to meet product performance, such as designing for corrosion resistance, instant high-temperature resistance, high strength in certain directions, good dielectric properties, etc.
6. **Excellent Processability:**
- Process selection can be flexible based on product shape, technical requirements, purpose, and quantity.
- Simple process, capable of single-step molding, economically advantageous, especially for complex-shaped, difficult-to-mold products in small quantities, showcasing superior process advantages.
**Disadvantages of FRP:**
1. **Low Elastic Modulus:**
- FRP's elastic modulus is twice that of wood but ten times less than steel (E=2.1×10^6). Therefore, in product structures, there is often insufficient rigidity leading to easy deformation. This can be compensated by thin-shell structures, sandwich structures, or using high-modulus fibers or reinforcement ribs.
2. **Poor Long-Term Temperature Resistance:**
- Most FRPs cannot be used long-term at high temperatures. General polyester FRPs show a significant drop in strength above 50°C and are typically used below 100°C. General epoxy FRPs lose strength significantly above 60°C. However, selecting heat-resistant resins allows for long-term use at 200-300°C.
3. **Aging Phenomenon:**
- Aging is a common defect in plastics, and FRP is no exception. Under the effects of ultraviolet rays, wind, sand, rain, snow, chemical media, and mechanical stress, performance degradation can occur.
4. **Low Interlaminar Shear Strength:**
- Interlaminar shear strength is borne by the resin, so it is very low. Methods like selecting appropriate processes and using coupling agents can improve interlaminar adhesion. Primarily, during product design, efforts should be made to avoid interlaminar shear.
**FRP Manufacturing Methods:**
Broadly divided into two categories: wet contact methods and dry pressure molding. Based on process characteristics, there are hand lay-up molding, laminating molding, RTM method, pultrusion, compression molding, filament winding, etc. Hand lay-up molding includes hand lay-up, bag pressing, spraying, wet lay-up under low pressure, and moldless hand lay-up.
Currently, the four most widely used molding methods globally are:
1. **Hand Lay-Up Method:** Mainly used in Norway, Japan, UK, Denmark, etc.
2. **Spray Method:** Mainly used in Sweden, USA, Norway, etc.
3. **Compression Molding Method:** Mainly used in Germany, etc.
4. **RTM Method:** Mainly used in Europe, America, and Japan.
In China, over 90% of FRP products are produced using the hand lay-up method, with others including compression molding, filament winding, and laminating molding (see Chapter 11). In Japan, the hand lay-up method still accounts for 50%. Globally, the hand lay-up method still holds a significant proportion, indicating its continued viability. The hand lay-up method uses wet resin molding, with simple equipment and low costs, allowing for the production of whole products over 10 meters in length. Disadvantages include low mechanization, long production cycles, and unstable quality. Recently, China has introduced extrusion, spraying, and filament winding process equipment from abroad, and with the development of the FRP industry, new process methods will continue to emerge.
**Applications of FRP:**
FRP (Fiber-Reinforced Plastic), also known as GRP, refers to fiber-reinforced plastics, usually glass fiber-reinforced unsaturated polyester, epoxy resin, and phenolic resin matrices. Using glass fibers or their products as reinforcing materials, it is referred to as glass fiber-reinforced plastic or fiberglass. Due to the different types of resins used, there are classifications such as polyester fiberglass, epoxy fiberglass, and phenolic fiberglass. Lightweight, hard, non-conductive, with high mechanical strength, limited recyclability, and corrosion resistance, it can replace steel in manufacturing machine parts, automobile, and ship hulls. FRP has been widely used in aerospace, railways, decorative architecture, home furniture, advertising displays, craft gifts, building materials, yachts, sports materials, environmental hygiene projects, and many other industries, earning widespread acclaim and becoming a sought-after material in the modern market. Its ease of shaping, customization, and color flexibility makes it highly favored by merchants and sellers, increasing its market share and offering broad prospects.
It finds application in various industries including black metallurgy, non-ferrous metallurgy, power, coal, petrochemicals, chemical industry, machinery and electronics, textiles, automotive and motorcycle manufacturing, railways, shipbuilding, construction, light industry, food, electronics, telecommunications, culture, sports and entertainment, agriculture, commerce, pharmaceuticals and health care, as well as military and civilian applications across various sectors. Specific products include mine ventilation equipment, coke-related equipment, rare earth smelting and iron alloy smelting equipment, cold rolling and electroplating equipment, transmission and transformation equipment, wind power generation equipment, cooling water pipes for thermal power plants, cooling water equipment, power management and maintenance tools, mine air ducts, explosion-proof water bags, explosion-proof devices, petroleum extraction related parts and equipment, petrochemical equipment, chemical equipment, chemical construction materials, mine ventilation equipment, motor parts, accessories, electroplating equipment, wind turbines and components, textile dyeing equipment, facilities and components, automotive manufacturing materials and components, automotive repair materials, motorcycle manufacturing materials and components, railway locomotive vehicle materials and related facilities, railway signal system materials and related components, various river, lake, and sea boats, large steel boat parts and accessories, building facilities and materials, bathrooms, kitchens, doors and windows, corrugated tiles, cooling towers, building ventilation and air conditioning facilities, building templates, light industrial daily chemicals and papermaking industry-related facilities, home appliances, alcohol, leather, furniture materials, food storage tanks, electronic industry equipment, consumer goods materials and electronic equipment accessories, postal and telecommunication equipment supporting facilities, sports equipment, amusement equipment and related facilities, agricultural irrigation equipment, greenhouses, agricultural machinery accessories, cold storage, aquaculture, commercial counters, commercial packaging boxes, commercial refrigerators, pharmaceutical industry facilities and medical and health purposes, etc.