Overview of Carbon Fiber Composite Material Forming Process

 

Brief Analysis Of Carbon Fiber Composite Material Molding Process And Application

 

Fiber-reinforced resin-based composite materials began in the 1930s and have a history of less than 100 years, but there are more than 20 processing technologies for composite materials. Although there are many types of processes, they are all derived from the same basis according to different material characteristics and usage requirements.

 

Carbon fiber has the characteristics of light weight and high strength. Technicians need to choose different molding processes according to the use requirements of carbon fiber composite materials in different application scenarios, and choose molding processing technology based on the comprehensive consideration of production costs on the basis of giving full play to the advantages of material performance.

 

1. Hand Lay-up Molding

 

Apply release agent and gel coat on the working surface of the mold, lay the cut carbon fiber prepreg on the working surface of the mold, brush or spray the resin system glue, and after reaching the required thickness, mold, cure and demold. Today, with the highly developed preparation technology, the hand lay-up process is still widely used in many fields such as petrochemical containers, storage tanks, and automobile shells with its advantages of simple process, low investment, and wide application.

 

Its disadvantages are loose texture, low density, low product strength, and it mainly relies on manual labor, unstable quality, and low production efficiency.

 

Schematic Diagram Of Hand Lay-up Molding Process

 

2. Spray Molding

It is a type of low-pressure molding in hand lay-up process. After the chopped fiber and resin are mixed by a spray gun, compressed air is sprayed on the mold. After reaching the predetermined thickness, it is pressed manually with a rubber roller and then cured.

 

A semi-mechanized molding process created to improve hand lay-up molding, which has a certain degree of improvement in work efficiency and is used to manufacture transition layers for automobile bodies, ship hulls, bathtubs, and storage tanks.

 

Schematic Diagram Of Injection Molding

 

3. Compression Molding

 

Place the carbon fiber prepreg between the upper and lower molds, close the mold and place the mold on the hydraulic molding table. After a certain period of high temperature and high pressure to solidify the resin, remove the carbon fiber product. This molding technology has the advantages of high efficiency, good product quality, high dimensional accuracy, and little environmental impact. It is suitable for batch and high-strength composite parts.

 

Although the compression molding process has a long history of application in Europe and the United States, it is still a very applicable carbon fiber molding process in China. It has an irreplaceable position in the manufacture of industrial load-bearing structural parts. Due to the controllable resin content, good fiber wettability, and high carbon fiber content in the finished product, the strength performance is excellent, the precise product size, short molding cycle, and good production environment can meet the large-scale production of 50,000 to 80,000 pieces per year.

 

 

 

4. Winding Molding

 

The process of winding continuous fibers or cloth tapes impregnated with resin glue onto a core mold according to a certain pattern, and then curing and demolding to form a composite material product. Carbon fiber winding molding can give full play to its high specific strength, high specific modulus and low density, and can be used to manufacture cylinders, spheres and certain positive curvature rotational bodies or cylindrical carbon fiber products.

 

Winding Process Flow Chart

 

Schematic Diagram Of Winding Process

 

5. Resin Transfer Molding

 

Resin transfer molding is a process technology in which low-viscosity resin flows in a closed mold, infiltrates reinforcement materials and solidifies into shape. It belongs to the category of liquid forming or structural liquid forming technology of composite materials. The specific method is to pre-place reinforcement materials that have been reasonably designed, cut or pre-formed by mechanization in the designed mold. The mold must have a peripheral seal and tightening, and ensure smooth flow of resin; after closing the mold, a certain amount of resin is injected, and after the resin is solidified, the desired product can be demolded. HP-RTM, VARTM, L-RTM, etc. are all improved molding methods of this process.

 

Resin Transfer Molding Process Flow Chart

 

Schematic Diagram Of Resin Transfer Molding Process

 

6. Pultrusion

 

The continuous carbon fiber tow, tape or cloth impregnated with resin glue is formed and cured through an extrusion die under the action of traction to continuously produce profiles of unlimited length. Pultrusion is a special process in the composite material molding process. Its advantage is that the production process can be fully automated and the production efficiency is high.

 

The fiber mass fraction in the pultruded product can be as high as 80%. The impregnation is carried out under tension, which can give full play to the role of the reinforcing material. The product has high strength, and the longitudinal and transverse strength of the finished product can be adjusted arbitrarily to meet the different mechanical properties requirements of the product. This process is suitable for the production of profiles with various cross-sectional shapes, such as I-shaped, angle-shaped, groove-shaped, special-shaped cross-sectional pipes and combined cross-sectional profiles composed of the above cross-sectional shapes.

 

Schematic Diagram Of Pultrusion Process

 

Typical Products Of Pultrusion Molding Process

 

7. Vacuum Autoclave Molding

 

Put the composite material blank formed by stacking single-layer prepreg in a predetermined direction in an autoclave and complete the curing process at a certain temperature and pressure. Autoclave is a special pressure vessel that can withstand and regulate a certain temperature and pressure range. The blank is laid on the surface of the mold with a release agent, and then covered with porous anti-stick cloth (film), adhesive felt, and breathable felt in turn, and sealed in a vacuum bag, and then placed in the autoclave.

 

Before heating and curing, the bag is first evacuated to remove air and volatiles, and then heated, pressurized, and cured according to the curing system of different resins. The formulation and implementation of the curing system are the key to ensuring the quality of autoclave molding parts. This molding process is suitable for manufacturing aircraft doors, fairings, airborne radar covers, brackets, wings, tails and other products.

 

Autoclave Molding Process Flow Chart

 

 

Schematic Diagram Of Autoclave Vacuum Bag Packaging

 

Schematic Diagram Of Autoclave Molding Process

 

8. Other Molding Processes

 

Lamination Molding:

The prepregs stacked layer by layer are placed between the upper and lower flat molds for pressurization and heating for curing. This process can directly inherit the production method and equipment of wood plywood, and improve and perfect it according to the rheological properties of the resin. The lamination molding process is mainly used to produce composite panels of various specifications and different uses. It has the characteristics of high mechanization and automation, stable product quality, etc., but the one-time investment in equipment is large.

 

Vacuum Introduction:

VIP for short, lay “dry” carbon fiber composite materials on the mold, then lay vacuum bags, and extract the vacuum in the system to form a negative pressure in the mold cavity. The pressure generated by the vacuum is used to press the unsaturated resin into the fiber layer through the pre-laid pipeline, so that the resin can infiltrate the reinforcing material and finally fill the entire mold. After the product is cured, the vacuum bag material is removed to obtain the desired product from the mold.

 

This process was patented in 1950, but it has only been developed in recent years. In a vacuum environment, the resin impregnates the carbon fiber, and very few bubbles are generated in the product. The product has higher strength and lighter quality. The product quality is relatively stable, and the loss of resin is reduced. Only one mold can be used to obtain a product with smooth and flat surfaces on both sides, and the thickness of the product can be better controlled.

 

It is generally used in rudders and radar shields in the boat industry, blades and engine covers in wind power energy, and various roofs, windshields, and compartments in the automotive industry.

 

3iTech Induction Heating:

 

A new induction heating process that integrates sensors in the mold can process carbon fiber at temperatures of 20℃-400℃, and heat the mold surface by using sensors integrated inside the mold through heat conduction.

 

This is a supplementary technology launched by the emerging company RocTool on the Cage system. Electromagnetic induction can quickly heat the mold and can well control the local temperature. Its advantage is that the cycle time and component cost are significantly reduced. However, this technology is not suitable for large components at present, and the relevant output must be large enough.

 

 

Liquid Molding:

The process of synthesizing liquid monomers into high molecular polymers and then curing the polymers into composite materials is changed to be completed directly in the mold at the same time, which not only reduces the energy consumption in the process, but also shortens the molding cycle (it only takes about 2 minutes to complete a product). However, the application of this process must be based on precise pipeline transportation and metering as well as automatic temperature and pressure control. It belongs to the intersection of polymer materials and modern high-tech science and technology, and its current application is not very wide.

 

With the deepening and development of the application of carbon fiber composite materials, the molding methods of carbon fiber composite materials are constantly emerging in new forms. However, the various molding processes of carbon fiber composite materials do not exist in a way of updating and elimination. In actual applications, multiple processes often coexist to achieve the best effect under different conditions and different circumstances.

 

Carbon Fiber Production and Processing Technology

 

1. What is Carbon Fiber?

• Carbon fiber refers to fibers in which carbon accounts for more than 90% of the total mass in the chemical composition of the fiber. Since carbon is insoluble in various solvents, it will not melt at high temperatures in an inert atmosphere isolated from air (under normal pressure). Only at a high temperature above 3800K can it be directly sublimated without dissolution.

 

Therefore, carbon fiber cannot be manufactured by melt spinning or solution spinning like general synthetic fibers, and the production conditions are very harsh.

 

The density of general carbon fiber is 1750kg/cubic meter, which is less than 1/4 of steel, and its tensile strength is generally above 3500MPa, which is 7-8 times that of steel, and its elastic modulus is 23000MPa-43000MPa, which is also higher than steel. Lightweight design of automobiles has always been one of the main research directions of automobiles, and carbon fiber may become a breakthrough direction.

 

The current development trend of body materials is diversified, including light metal materials such as aluminum alloy and magnesium alloy. The future development direction of body materials is to improve the strength of materials to reduce the weight of the body. The use of carbon fiber composite materials in automobiles can ensure their safety performance.

 

• Carbon fiber reinforced composite materials have two major characteristics: strong tensile strength of carbon materials and soft processability of fibers. Carbon fiber is a new material with excellent mechanical properties, and its strength is significantly higher than that of glass fiber (GFRP).

 

 

2. What are the Carbon Fiber Processing Technologies?

 

Cutting:

Cut the carbon cloth of appropriate size (slightly larger). To make an ideal carbon fiber product, molds need to be made. It is also divided into female molds and male molds, which depends on the specific details of the product. (Warm reminder: Wear protective equipment from the beginning of processing)

 

Laying:

Lay the prepreg on the tooling. Change the angle, method or number of layers according to the design requirements, and its performance will be different. During the laying, laser positioning is used, and each layer is laid layer by layer and checked layer by layer. Each layer is laid in place.

 

Molding:

Place the carbon fiber prepreg between the upper and lower molds, close the mold and place the mold on the hydraulic molding table. After a certain period of high temperature and high pressure to solidify the resin, remove the carbon fiber product. This compression molding (PCM) technology has the advantages of high efficiency, good product quality, high dimensional accuracy, and little environmental impact. It is suitable for batch and high-strength composite parts molding.

 

Processing:

After carbon fiber molding, burrs need to be removed. For precision requirements or assembly needs, post-processing such as cutting and drilling is also required. Due to the unevenness of carbon fiber, fiber pullout or matrix fiber detachment often occurs during processing. In addition, carbon fiber has high heat resistance and wear resistance, which makes it have high requirements on equipment during processing. Therefore, a large amount of cutting heat generated during the production process causes serious wear on the equipment.

 

 

3. Application Of Carbon Fiber Products in the Racing Field

• With the development of the automobile industry, more and more carbon fiber products are used in racing vehicles. In FSC events, some teams also use monocoques, and the manufacturing process requirements of monocoques are also very high. However, compared with the steel tube frame, it has many advantages. They are all cold-processed, which minimizes assembly errors and lays the foundation for suspension, steering, and wheel edges.

 

In the aerodynamic components of the body, the front and rear wings, diffusers, etc. can all be made into carbon fiber kits. Excellent teams have products comparable to those produced and sold.

 

 

3. Application Of Carbon Fiber Products in The Racing Field

• With the development of the automobile industry, more and more carbon fiber products are used in racing vehicles. In FSC events, some teams also use monocoques, and the manufacturing process requirements of monocoques are also very high. However, compared with the steel tube frame, it has many advantages. They are all cold-processed, which minimizes assembly errors and lays the foundation for suspension, steering, and wheel edges.

 

In the aerodynamic components of the body, the front and rear wings, diffusers, etc. can all be made into carbon fiber kits. Excellent teams have products comparable to those produced and sold.

 

Figure 1 Schematic Diagram Of The Spraying Process

 

1.2. Main Materials

The resin matrix is ​​mainly polyester resin, while the fiber material is limited to glass fiber roving.

 

1.3. Main Advantages

1. i) Widely used for many years.
2. ii) A method for quickly depositing fibers and resins.

iii) Low cost.

 

1.4. Main Disadvantages

1. i) Laminates tend to be rich in resin and therefore too heavy.
2. ii) Contain only short fibers, which severely limits the mechanical properties of the laminate.

iii) Resins require low viscosity for spraying, which often impairs their mechanical/thermal properties.

1. iv) High styrene content in spray resins generally means they are more hazardous, and their lower viscosity means they have a greater tendency to penetrate clothing, etc.

(v) It is increasingly difficult to limit the concentration of styrene in the air to legal levels.

 

1.5. Typical Applications Simple Shells, Light-loaded Structural Panels, Such as Caravan Bodies, Truck Fairings, Bathtubs, Shower Trays, Some Boats.

 

2. Filament Winding

 

2.1. Process Concept

This process is mainly used for hollow, usually round or oval parts such as pipes and tanks. The fiber bundle is passed through a resin bath before being wound onto the mandrel, and the rotation speed of the mandrel is controlled by the fiber delivery mechanism and the direction of the mandrel (Figure 2)

 

Figure 2 Schematic diagram of filament winding process

 

2.2. Main Materials

The resin matrix can be any of epoxy, polyester, vinyl ester, phenolic resin, etc., and there is no restriction on the fiber type, but the fibers can be taken directly from the creel without being woven into fabric.

 

2.3. Main Advantages

1. i) This is a very fast and economical way to lay the material.
2. ii) The resin content can be controlled by measuring the resin on each fiber bundle through the clamp or mold.

iii) Since there is no second process to convert the fiber into fabric before use, the fiber cost is minimized.

1. iv) The structural properties of the laminate can be very good because straight fibers can be laid in complex patterns to match the applied load.

 

2.4. Main Disadvantages

1. i) The process is limited to convex parts.
2. ii) The fibers cannot be easily laid along the length of the component.

iii) Large components can be costly.

1. iv) The outer surface of the component is not molded, so it is not aesthetically pleasing.
2. v) Low viscosity resins are usually required because they have lower mechanical and safety properties.

 

2.5. Typical Applications

Chemical storage tanks and pipelines, gas cylinders, firefighter breathing tanks

 

3. Wet Lay-up

 

3.1. Process Concept

The resin is impregnated into fibers in the form of woven, knitted, stitched or bonded fabrics by hand. This is usually done by rollers or brushes, and increasingly, press roller impregnation agents are used, where the resin is pressed into the fabric by rotating rollers and resin baths, and the laminate is cured under standard atmospheric conditions (as shown in Figure 3).

 

 

3.2. Main Materials

The resin matrix can be any of epoxy, polyester, vinyl ester, phenolic resin, etc., and there is no restriction on the fiber type.

 

3.3. Main Advantages

1. i) Widely used for many years.
2. ii) Low cost if room temperature curing resin is used.

iii) Wide selection of suppliers and material types.

1. iv) Higher fiber content and longer fiber length.

 

3.4. Main Disadvantages

1. i) The mixing of resins, the resin content of the laminate and the quality of the laminate depend largely on the technology of the laminator. It is usually not possible to obtain a low resin content laminate without introducing excessive voids.
2. ii) Health and safety considerations of resins. The lower molecular weight of hand-laid resins generally means that they are more harmful than higher molecular weight products. Lower viscosity resins also mean that they have a tendency to penetrate clothing, etc.

iii) It is increasingly difficult to limit the concentration of styrene in the air to legal concentrations in polyester and vinyl ester without expensive extraction systems.

1. iv) The resin needs to be of low viscosity for manual operation. This often compromises their mechanical/thermal properties due to the high concentration of diluent/styrene required.

 

3.5. Typical Applications

Standard wind turbine blades, production boats, architectural trim strips, etc.

 

4. Vacuum Bagging

 

4.1. Process Concept

This process is basically an extension of the wet-lay process described above, where pressure is applied to the laminate once it has been laminated to improve its consolidation. This is achieved by sealing a plastic film over the wet-laid laminate and over the tool. The air under the bag is evacuated by a vacuum pump, so that up to one atmosphere of pressure can be applied to the laminate to cure it (Figure 4).

 

4.2. Main Materials

The resins are mainly epoxy and phenolic resins, while polyesters and vinyl esters may have some problems because the vacuum pump over-extracts styrene from the resin. For reinforcing fibers, the presence of a certain consolidation pressure means that various heavy fabrics may get wet.

 

Figure 4 Schematic diagram of vacuum bag process

 

4.3. Main Advantages

1. i) Compared with standard wet laying technology, higher fiber content laminates can usually be obtained.
2. ii) Lower void content compared with wet laying.

iii) Due to pressure and resin flow in the structural fibers, the fibers are better wetted and excess fibers enter the bagged material.

1. iv) Health and safety: vacuum bags reduce the amount of volatiles released during curing.

 

4.4. Main Disadvantages

1. i) Additional processes increase the cost of labor and disposable packaging materials
2. ii) Operators require a higher level of skill

iii) Mixing and control of resin content still depends mainly on the skills of the operator

1. iv) Although vacuum bags can reduce volatiles, the exposure is still higher than prepreg processing technology, etc.

 

4.5. Typical Applications

Large disposable cruise boats, racing parts, core bonding devices in production boats.

 

5. Pultrusion

 

5.1. Process Concept

The fiber is pulled from the creel through a resin bath and then through a heated mold. The die impregnates the fibers, controls the resin content, and solidifies the material into its final shape as it passes through the die. This solidified profile is then automatically cut to length. Fabric can also be introduced into the die to provide fiber orientations other than 0°. Although pultrusion is a continuous process that produces a profile of constant cross-section, some variation is allowed to be introduced into the cross-section. The process pulls the material through a die for impregnation and then clamps it in the die for curing. This makes the process discontinuous, but can accommodate small variations in cross-section (as shown in Figure 5).

 

Figure 5 Schematic Diagram Of Pultrusion Process

 

5.2 Main Materials

The resin matrix is ​​generally epoxy, polyester, vinyl ester and phenolic resin, while the fiber type is not limited.

 

5.3 Main Advantages

1. i) This is a very fast and economical method of impregnating and curing materials.
2. ii) The resin content can be precisely controlled.

iii) The fiber cost is minimized because most of it comes from the creel.

1. iv) The structural properties of the laminate are very good because the fibers in the profile are straight and a high fiber volume fraction can be obtained.
2. v) The resin impregnation area can be closed, thereby limiting volatile emissions.

 

5.4 Main Disadvantages

1. i) Limited to constant or nearly constant cross-section components
2. ii) The cost of heating the mold can be high.

 

5.5 Typical Applications

Beams and girders used for roof structures, bridges, ladders, frames.

 

6. Resin Transfer Moulding (RTM)

 

6.1. Process Concept

The fabrics are stacked as dry materials, which are sometimes pre-pressed into the mold shape and bonded together by adhesives, and then these “preforms” are placed into the mold more easily. The second mold is then clamped to the first mold and the resin is injected into the cavity. A vacuum can also be applied to the mold cavity to help the resin be drawn into the fabric. This is called Vacuum Assisted Resin Injection (VARI). Once all the fabrics are wetted, the resin inlet is closed and the laminate can be cured. Both injection and curing can be performed at ambient temperature or elevated temperature (as shown in Figure 6).

 

Figure 6 RTM Process Schematic

 

6.2. Main Materials

Resins can usually be epoxy, polyester, vinyl ester and phenolic, but high temperature resins such as bismaleimide can also be used at higher process temperatures. The fiber type is not limited, and sewn materials work well in this process because the gaps allow for rapid resin transport. Some specially developed fabrics can help the resin flow.

 

6.3. Main Advantages

1. i) Laminates with high fiber volume can be obtained at very low voids.
2. ii) Good health and safety and environmental control due to encapsulated resin.

iii) Possible labor reduction.

1. iv) Both sides of the component have a molding surface.

 

6.4. Main Disadvantages

1. i) The matching mold is expensive and heavy to withstand the pressure.
2. ii) Generally limited to smaller parts.

iii) Unimpregnated areas may occur, resulting in very expensive scrapped parts.

 

6.5. Typical Applications

Small complex aircraft and automotive parts, train seats.

 

7. Other Injection Molding Processes (SCRIMP, RIFT, VARTM, etc.)

 

7.1. Process Concept

Similar to the RTM process, the fabric is placed as a dry material stack, and then the fiber stack is covered with a peel layer and a woven non-structural fabric. The entire dry stack is then vacuum bagged, and once the bagging leaks are eliminated, the resin can flow into the laminate. The resin flows easily in the non-structural fabric and wets the fabric from above, which helps the distribution of the resin throughout the laminate (as shown in Figure 7).

 

7.2. Main Materials

The resin is generally epoxy, polyester and vinyl ester. The reinforcement fiber is any conventional fabric, and sewn materials work well in this process because the gap allows for rapid resin transport.

 

Figure 7 Schematic Diagram Of Other Injection Molding Processes

 

7.3. Main Advantages

1. i) Same as RTM above, but only one side of the part has a molded finish.
2. ii) Lower tooling costs because half of the tool is a vacuum bag and the strength required for the main tool is lower.

iii) Very large structures with high fiber volume fraction and low void content can be manufactured.

1. iv) Standard wet layup tools can be modified during the process.
2. v) Cored structures can be produced in a single operation.

 

7.4. Main Disadvantages

1. i) Relatively complex process that can continue to work well on large structures without the need for repairs.
2. ii) The viscosity of the resin must be very low, so the mechanical properties must be good.

iii) Unimpregnated areas may occur, resulting in very expensive scrapped parts.

 

7.5 Typical Applications

Small yachts, train and truck body panels, wind energy blades.

 

8. Autoclave Prepreg (Prepreg – Autoclave)

 

8.1. Process Concept

Fabrics and fibers are pre-impregnated with resin by the material manufacturer under heat and pressure or in a solvent. The catalyst is highly latent at ambient temperature, giving the material a useful life of weeks or months after thawing. However, to extend the shelf life, the materials must be stored frozen. The prepreg is placed on the mold surface by hand or machine, vacuum packed, and then heated to 120-180°C, which causes the resin to reflow and eventually cure. The additional pressure required for molding is usually provided by an autoclave (actually a pressurized oven) that applies up to 5 atmospheres of pressure to the laminate, as shown in Figure 8.

 

 

Figure 8 Schematic Diagram Of the Autoclave Prepreg Process

 

8.2. Main Materials

The resin matrix is ​​generally epoxy resin, polyester resin, phenolic resin and high temperature resin such as polyimide, cyanate ester and bismaleimide. The fiber type is not limited and can be taken directly from the creel or used as any type of fabric.

 

8.3. Main Advantages

1. i) The resin/catalyst and the resin content in the fiber can be precisely set, and high fiber content and low void content can be achieved.
2. ii) It has excellent health and safety characteristics and can work cleanly.

iii) The fiber cost of unidirectional tape is minimized because there is no second process to convert the fiber into fabric before use.

1. iv) The resin chemistry can be optimized for mechanical and thermal properties, and high viscosity resins are not easily soluble due to the manufacturing process.
2. v) The extended working time (up to several months at room temperature) means that structural optimization and complex layups can be easily achieved.
3. vi) Automation and labor savings can be achieved.

 

8.4. Main Disadvantages

1. i) The material cost of prepreg fabrics is high, and expensive advanced resins are usually required for these applications.
2. ii) Autoclaves are usually required to cure the components, which is expensive, slow and limited in size.

iii) The mold must be able to withstand the process temperatures involved, and the core material must be able to withstand the process temperatures and pressures.

1. iv) For thicker laminates, the prepreg layers need to be thermally “flushed” during the layup process to ensure the removal of air between the layers.

 

8.5. Typical Applications

Aircraft structural components (such as wings and tail sections), Formula One racing cars

 

9. Prepreg – Out of Autoclave

9.1. Process Concept

Low-temperature curing prepregs are exactly the same as traditional autoclave prepregs, but their resins have chemical properties that can be cured at temperatures of 60-120°C. For low-temperature curing (60°C), the service life of the material can be limited to less than one week, but for higher temperature catalysis (>80°C), the working time can be up to several months. The flow curve of the resin system allows the use of vacuum bag pressure alone, eliminating the need for an autoclave (as shown in Figure 9).

 

9.2. Main Materials

The resin is usually only epoxy resin. Any fiber type, conventional prepreg.

 

9.3. Main Advantages

1. i) All the advantages associated with using conventional prepregs listed above ((i)-(iv)) are included in low temperature cure prepregs.
2. ii) Due to the lower cure temperature, cheaper tooling materials such as wood can be used.

iii) Large structures can be easily manufactured as only vacuum bag pressure is required, and the temperature can be heated to these lower temperatures by a simple hot air circulating oven (usually built in situ on the part).

1. iv) Conventional foam core materials can be used if certain procedures are followed.
2. v) Lower energy consumption than autoclave processes.
3. vi) Provides high levels of dimensional tolerance and repeatability.

 

Figure 9 Schematic Diagram Of The Non-Autoclave Prepreg Process

 

9.4. Main Disadvantages

1. i) Although the resin cost is lower than that required for aerospace applications, the material cost is still higher than non-prepreg fabrics.
2. ii) The tool must be able to withstand higher temperatures than the infusion process (typically 80-140°C).

 

9.5. Typical Applications

High-performance wind turbine blades, large racing and cruising yachts, rescue boats, train components.