FRP Products Molding Technology

Resin-based composite materials, commonly known as FRP (Fiber Reinforced Plastics / GRP), are a class of composites composed of resin and fiber reinforcement. They possess unique advantages such as high specific strength and specific stiffness, excellent designability, good fatigue resistance, superior corrosion resistance, suitability for large-area integral molding, and special electromagnetic properties.

Compared with traditional structural materials such as steel and aluminum alloy, the density of resin-based composites is approximately 1/5 of steel and 1/2 of aluminum alloy, while their specific strength and specific modulus are higher. Under the same strength and stiffness requirements, resin-based composites can effectively reduce structural weight.

In addition to the type and content of fibers and resin, the mechanical and physical properties of resin-based composites are also closely related to fiber orientation, layup sequence and ply quantity. According to different service conditions, appropriate materials and layup designs can be adopted to meet design requirements with safety, reliability and cost-effectiveness. Therefore, they have been widely applied in construction, shipbuilding, electrical engineering, aerospace and other fields, becoming a fast-growing and widely used type of composite material.

I. Material Composition

FRP mainly consists of two parts: matrix material and reinforcement material.

The reinforcement acts as the supporting skeleton of fiber-reinforced composites, fundamentally determining the mechanical properties of FRP products. It also improves material shrinkage, heat distortion temperature, electromagnetic performance and thermophysical properties to a certain extent.

The resin matrix bonds the reinforcements into an integral whole, serving to transfer and balance loads so that the reinforcement can fully exert its mechanical advantages. Properties such as heat resistance, chemical corrosion resistance, flame retardancy, weather resistance, electrical insulation and electromagnetic performance of composites all depend on the resin matrix. Meanwhile, the resin matrix also influences the impact resistance and mechanical properties of composites to varying degrees.

1. Resin Matrix

A wide range of thermosetting and thermoplastic plastics can be used as composite resin matrices.

Common thermosetting resins:

Unsaturated polyester, vinyl ester, epoxy, phenolic, bismaleimide, polyimide, etc.

Common thermoplastic resins:

Polypropylene, polycarbonate, nylon, polyethersulfone, etc.

2. Reinforcement Materials

Widely used reinforcements include glass fiber roving, glass fabric, continuous mat and chopped strand mat, as well as carbon fiber, aramid fiber and other high-performance fibers.

II. Molding Processes

Main FRP molding technologies include: Hand Lay-up, Compression Molding, RTM, Filament Winding, Pultrusion, etc.

1. Hand Lay-up Molding

It is barely restricted by product shape and size, with low mold cost. It is highly suitable for large-sized products with multiple varieties and small production volume.

2. Compression Molding

Suitable for mass-produced products with precise dimensional requirements. The compression mold consists of a male mold and a female mold. Reinforcements are generally chopped fiber mat, continuous fiber mat and woven fabric.

3. RTM (Resin Transfer Molding)

It is ideal for producing multi-variety, medium-batch and high-quality composite products.

Advantages:

Manufactures complex composite components with high quality, high precision, low void content and high fiber content;

Achieves smooth double-sided surfaces without gel coat resin;

Short lead time from design to mass production with high efficiency;

Molds and products can be designed by CAD, featuring easy mold manufacturing and wide material selection;

Local reinforcement and thickened structure can be realized easily; composite parts with core materials can be formed in one step;

Low volatile content, favorable for labor protection and environmental protection.

4. Filament Winding Molding

Filament winding is a process in which resin-impregnated fibers are wound uniformly and regularly onto a rotating mandrel by a dedicated winding machine, followed by curing and mandrel removal to obtain finished parts.

It is suitable not only for simple revolving bodies such as cylinders, tanks, pipes, spheres and cones, but also for non-revolving components like aircraft fuselages and automotive body parts.

Main advantages: Raw material saving, low production cost and high product repeatability.

Main disadvantages: Mandrel removal required after curing; not applicable to products with concave curved surfaces.

5. Pultrusion Molding

Used for continuous production of fiber composite profiles. Raw materials are pulled through a heated die with a fixed cross-section to complete compounding, forming and curing. The pultrusion process features simple workflow and high efficiency. Reinforcement fibers are arranged parallel to the axial direction during pultrusion.

Mechanically Wound FRP Pipe

Mechanically wound FRP pipe is a lightweight, high-strength and corrosion-resistant non-metallic pipe. It is manufactured with resin as matrix and glass fiber as reinforcement via special processes.

It features excellent corrosion resistance, anti-leakage performance and thermal insulation; lightweight & high strength, long service life, flexible designability, low fluid resistance, easy installation and low comprehensive cost.

Widely used in petroleum, chemical, pharmaceutical, electric power, papermaking, urban water supply and drainage, industrial wastewater treatment, seawater desalination, gas transmission, mining and other industries, it is an ideal pipeline for liquid and gas transportation. In recent years, China’s FRP pipe industry has developed rapidly with increasing output and expanding application scope.

Fitting Types

Socket type, butt joint type, flange type, O-ring type; elbow, tee, reducer, flat welding flange, etc.

Main Pipe Categories

Pure FRP pipe, sand-filled FRP pipe, high-pressure pipe, thermal insulation pipe.

Structural Features

Excellent corrosion resistance: No additional anti-corrosion protection required; no secondary pollution to water or other media; long service life.

Light weight: Only 1/4 the weight of ductile iron pipe and 1/10 of cement pipe in same specification and length; easy transportation, handling and installation.

Long single pipe length: Reduces pipeline joints, speeds up installation and improves overall pipeline quality.

Smooth inner wall: Low flow resistance, higher flow velocity and lower energy consumption. Under the same flow rate, smaller pipe diameter can be adopted; flow capacity increases by about 10% compared with steel pipe of the same size. No scaling, stable flow rate in long-term service; good protection for cables in interference and heavy corrosion environments.

6. Brief Introduction to Pultrusion Process

Under the traction of a pultrusion machine, reinforcements such as glass fiber roving and glass yarn are impregnated in resin bath, then heated and shaped through a forming die to produce FRP profiles by mechanized composite molding.

FRP pultruded profiles are both structural and functional materials with outstanding design flexibility. Specific performance can be achieved by raw material selection and layup design. With years of production and design experience, our company can meet customers’ customized requirements.

Advantages of Pultruded Profiles

Corrosion resistance, anti-aging, flexible designability, lightweight & high strength, arbitrary cutting, easy installation, non-magnetic, non-conductive, customizable color.