**4.1 Open contact moulding**

Hand lay-up is an open contact moulding technique for fabricating composite materials. Resins are impregnated by the hand into fibres which are in the form of woven, knitted, stitched, or bonded fabrics. In this technique, the mould is first treated with mould release, dry fibres or dry fabrics are laid on a mould, and liquid resin is then poured and spread onto the fibre beds [36]. This is usually accomplished by rollers or brushes, with an increasing use of nip-roller-type impregnators for forcing resin into the fabrics by means of rotating rollers and a bath of resin. A roller or brush is used to wet the fibres and remove air trapped into the lay-ups. A few layers of fibres are wetted, and laminates are left to cure under standard atmospheric conditions. After these layers are cured, more layers are added, as shown in **Figure 2**.

Hand lay-up and spray-up methods are often used in tandem to reduce labour cost. This is a common process for making glass fibre composite products such as bathtubs, boat hulls and decks, fenders, RV components, shower stalls, spas, truck

With the ever-increasing demand for faster production rates, the industry has used alternative fabrication processes to replace hand lay-up as well as encouraged

Resin transfer moulding (RTM), sometimes referred to as liquid moulding, is a

Reaction injection moulding (RIM) injects a rapid cure resin and a catalyst into

Representing the fastest-growing moulding technology is vacuum-assisted resin transfer moulding (VARTM), as shown in **Figure 5**. The difference between VARTM and RTM is that in VARTM, resin is drawn into a preform use a vacuum only, rather than pumped in under pressure as RTM. VARTM technique does not require high heat or pressure. VARTM usually operates with low-cost tooling, making it possible

Resin film infusion (RFI) is a hybrid process in which a dry preform is placed in a mould on top of a layer, or interleaved with multiple layers, of high-viscosity resin film. Under applied heat, vacuum, and pressure, the resin liquefies and is drawn into the preform, resulting in uniform resin distribution, even with high-viscosity, toughened resins, because of the short flow distance. Using the resin infusion techniques, the fibre volumes can be up to 70%, and automated controls ensure low voids and consistent preform reproduction, without the need for trimming. Resin infusion has found significant application in boatbuilding. This method has been

fairly simple process. In this technique, the mould is first treated with mould release. The dry reinforcement, typically a preform, is then placed into the mould and the mould is closed. Low viscosity resin and catalyst are metered and mixed and then pumped into the mould under low-to-moderate pressure through injection ports, following predesigned paths through the preform. Low-viscosity resin is used in RTM technique to ensure that the resin permeates through the preform quickly

and thoroughly before gel and cure, especially with thick composite parts.

to inexpensively produce large, complex parts in one shot [41–43].

the mould in two separate streams. Mixing and chemical reaction occur in the mould instead of in a dispensing head. Automotive industry suppliers have combined structural RIM (SRIM) with rapid preforming methods to fabricate structural parts that do not require a class A finish. **Figure 4** describes the schematic of the

cabs, and other relatively large and noncomplex shapes.

fabricators to automate those processes wherever possible.

**4.2 Resin infusion processes**

*Introduction to Composite Materials*

*DOI: http://dx.doi.org/10.5772/intechopen.91285*

RTM process [39, 40].

**Figure 4.**

**15**

*The schematic of the RTM process.*

Spray-up is also an open-mould application technique for composite. The spray lay-up technique is considered an extension of the hand lay-up method. In this process, the mould is first treated with mould release. If a gel coat is used, it is sprayed into the mould at a certain thickness after the mould release has been applied. The gel coat then is cured, and the mould is ready for process. The fibre and catalysed resin at a viscosity of 500–1000 cps are sprayed into the mould using a chopper spray gun. The gun chops continuous fibre tow into short-fibre bundle lengths and then blows the short fibres directly into the sprayed resin stream so that both materials are applied simultaneously on the surface of the mould, as shown in **Figure 3**. In the final steps of the spray-up process, the workers compact the laminate by hand with rollers. The composite part is then cured, cooled, and removed from the mould [37, 38].

**Figure 2.** *Hand lay-up process.*

**Figure 3.** *The schematic of the spray lay-up process.*

#### *Introduction to Composite Materials DOI: http://dx.doi.org/10.5772/intechopen.91285*

Hand lay-up and spray-up methods are often used in tandem to reduce labour cost. This is a common process for making glass fibre composite products such as bathtubs, boat hulls and decks, fenders, RV components, shower stalls, spas, truck cabs, and other relatively large and noncomplex shapes.

### **4.2 Resin infusion processes**

**4.1 Open contact moulding**

removed from the mould [37, 38].

**Figure 2.**

**Figure 3.**

**14**

*The schematic of the spray lay-up process.*

*Hand lay-up process.*

Hand lay-up is an open contact moulding technique for fabricating composite materials. Resins are impregnated by the hand into fibres which are in the form of woven, knitted, stitched, or bonded fabrics. In this technique, the mould is first treated with mould release, dry fibres or dry fabrics are laid on a mould, and liquid resin is then poured and spread onto the fibre beds [36]. This is usually accomplished by rollers or brushes, with an increasing use of nip-roller-type impregnators for forcing resin into the fabrics by means of rotating rollers and a bath of resin. A roller or brush is used to wet the fibres and remove air trapped into the lay-ups. A few layers of fibres are wetted, and laminates are left to cure under standard atmospheric conditions. After these layers are cured, more layers are added, as shown in **Figure 2**. Spray-up is also an open-mould application technique for composite. The spray lay-up technique is considered an extension of the hand lay-up method. In this process, the mould is first treated with mould release. If a gel coat is used, it is sprayed into the mould at a certain thickness after the mould release has been applied. The gel coat then is cured, and the mould is ready for process. The fibre and catalysed resin at a viscosity of 500–1000 cps are sprayed into the mould using a chopper spray gun. The gun chops continuous fibre tow into short-fibre bundle lengths and then blows the short fibres directly into the sprayed resin stream so that both materials are applied simultaneously on the surface of the mould, as shown in **Figure 3**. In the final steps of the spray-up process, the workers compact the laminate by hand with rollers. The composite part is then cured, cooled, and

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

With the ever-increasing demand for faster production rates, the industry has used alternative fabrication processes to replace hand lay-up as well as encouraged fabricators to automate those processes wherever possible.

Resin transfer moulding (RTM), sometimes referred to as liquid moulding, is a fairly simple process. In this technique, the mould is first treated with mould release. The dry reinforcement, typically a preform, is then placed into the mould and the mould is closed. Low viscosity resin and catalyst are metered and mixed and then pumped into the mould under low-to-moderate pressure through injection ports, following predesigned paths through the preform. Low-viscosity resin is used in RTM technique to ensure that the resin permeates through the preform quickly and thoroughly before gel and cure, especially with thick composite parts.

Reaction injection moulding (RIM) injects a rapid cure resin and a catalyst into the mould in two separate streams. Mixing and chemical reaction occur in the mould instead of in a dispensing head. Automotive industry suppliers have combined structural RIM (SRIM) with rapid preforming methods to fabricate structural parts that do not require a class A finish. **Figure 4** describes the schematic of the RTM process [39, 40].

Representing the fastest-growing moulding technology is vacuum-assisted resin transfer moulding (VARTM), as shown in **Figure 5**. The difference between VARTM and RTM is that in VARTM, resin is drawn into a preform use a vacuum only, rather than pumped in under pressure as RTM. VARTM technique does not require high heat or pressure. VARTM usually operates with low-cost tooling, making it possible to inexpensively produce large, complex parts in one shot [41–43].

Resin film infusion (RFI) is a hybrid process in which a dry preform is placed in a mould on top of a layer, or interleaved with multiple layers, of high-viscosity resin film. Under applied heat, vacuum, and pressure, the resin liquefies and is drawn into the preform, resulting in uniform resin distribution, even with high-viscosity, toughened resins, because of the short flow distance. Using the resin infusion techniques, the fibre volumes can be up to 70%, and automated controls ensure low voids and consistent preform reproduction, without the need for trimming. Resin infusion has found significant application in boatbuilding. This method has been

**Figure 4.** *The schematic of the RTM process.*

#### *Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

**Figure 5.**

*The schematic of the VARTM process.*

#### **Figure 6.**

*The schematic of the resin film infusion process.*

employed by The Boeing Co. (Chicago, IL, USA) and NASA, as well as small fabricating firms, to produce aerospace-quality laminates without an autoclave [36, 44]. **Figure 6** presents the schematic of the resin film infusion process.

nearly 150 years. Reciprocating screw injection-moulding machines were introduced in the 1960s and are still used today [45]. Injection speeds are typically one to a few seconds, and many parts can be produced per hour in some multiple cavity

Filament winding is a continuous fabrication method that can be highly automated and repeatable, with relatively low material costs as shown in **Figure 9**. A long, cylindrical tool called a mandrel is suspended horizontally between end supports. Dry fibres are run through a bath of resin to be wetted. The fibre application instrument moves back and forth along the length of a rotating mandrel with the traverse carriage, placing fibre onto the tool in a predetermined configuration. Computer-controlled filament-winding machines are used to arrange the axes of motion [46–48]. Filament winding is one example of aerospace composite

Composite pultrusion is a processing method for producing continuous lengths of fibre-reinforced polymer structural shapes with constant cross-sections. This is a continuous fabrication method that can be highly automated. In this process, a continuous bundle of dry fibre is pulled through a heated resin-wetting station.

moulds.

**Figure 8.**

**Figure 7.**

*The schematic of compression moulding process.*

*Introduction to Composite Materials*

*DOI: http://dx.doi.org/10.5772/intechopen.91285*

materials.

**17**

**4.5 Filament winding**

*Simplified diagram of moulding process.*

**4.6 Pultrusion process**

#### **4.3 Compression moulding**

Compression moulding is a precise and potentially rapid process for producing high-quality composite parts in a wide range of volumes. The material is manually or robotically placed in the mould. The mould halves are closed, and pressure is applied using hydraulic presses. Cycle time ranges depending on the part size and thickness. This process produces high-strength, complex parts in a wide variety of sizes. The composites are commonly processed by compression moulding and include thermosetting prepregs, fibre-reinforced thermoplastic, moulding compounds such as sheet moulding compound (SMC), bulk moulding compounds (BMC), and chopped thermoplastic tapes. **Figure 7** shows the schematic of the compression moulding process.

#### **4.4 Injection moulding**

Injection moulding is a closed process as shown in **Figure 8**. This is fast, highvolume, low-pressure, and most commonly used for filled thermoplastics, such as nylon with chopped glass fibre. The injection-moulding process has been in use for

**Figure 7.** *The schematic of compression moulding process.*

nearly 150 years. Reciprocating screw injection-moulding machines were introduced in the 1960s and are still used today [45]. Injection speeds are typically one to a few seconds, and many parts can be produced per hour in some multiple cavity moulds.
