Composite Material Processing

A composite is a combination, or bond, between two or more dissimilar materials that unite into a newer material with superior properties. These can appear as either natural, or synthetic (manmade); and where advanced composites are both fabricated and assembled into a superior form. The original materials are still identifiable, retaining chemical, physical, or mechanical properties. But their bonding, the making of a composite, introduces new properties into the advanced material, such as strength, stretch, resistance, better resilience to fatigue, and overall durability.

Composites might, for example, be applied to high-speed rail operations meeting carbon neutral goals. Another application, operational safety of naval warships and other seafaring vessels relies on bespoke material design and supply to navigate unpredictable sea-scapes.

Above: Permali’s Tower Impregnator

 

Types of Composite Manufacturing Processing

Broadly, material processing is a science. It concerns how materials change from one shape to another. There are three major types of composite manufacturing processes, or moulding categories, known as open moulding, closed moulding, polymer moulding.

When determining the proper technique, an engineer will have to study the options, and the materials involved, to understand its performance, production, and cost effectiveness of its application.

What is Open Moulding?

As suggested by its name, this technique is achieved whereby composite materials are placed into an open mould, exposed to the air, and left to ‘cure’ or harden.

As a more inexpensive and flexible fabrication technique, Open Moulding can be ideal for prototyping, or anything with shorter production runs. It can also seem limitless for its design options.

Within this branch of composite manufacturing unpacks a series of processes, including:

·         Hand Lay-up

Perhaps the most common, if inexpensive, of the many processes, Hand Lay-up is the technique of brushing, or rolling, resin in a mould with a brush (by hand). It’s a technique that can be flexible to different sizes of production, including the creation of boat parts.

 

·         Spray-up

Using special equipment, the Spray-up process involves a chopper gun, like an electric paint sprayer. Not only does it shorten fibres, but also applies a mixture onto a moulding surface. As a more automated alternative to Hand Lay-up, this process is better for larger production quantities.

·         Filament Winding

As more labour-efficient, if automated, process, filament winding threads strands of fibre reinforcements over its mould. This process is most commonly used for hollow products like pipes.

What is Closed Moulding?

Unlike an open Mould, this technique is sealed off from the external atmosphere. Composite materials are cured inside a vacuum, or two-sided mould, essentially a closed off cavity.

There are many distinct reasons that material engineers opt for a Closed Moulding technique. Partly, a Closed Mould helps with product desirability, such as forming a product with a two-sided finish or to a higher quality. Alternatively, a Closed Mould helps with highly productive runs for increased volume manufacturing.

Though the call for capital investment is higher, this technique is ideal for manufacturing products at a greater volume to create better parts, more consistently, and with less waste. Another benefit of Closed Moulding, the results produce a better cosmetic finish, reducing the need for post-work.

Within this branch of composite manufacturing unpacks a series of automated, highly productive processes.

  • Vacuum Bag Moulding

Vacuum bag moulding is an improvement on open mould laminates using external atmospheric pressure.

 

  • Vacuum Infusion Processing (VIP)

Utilizing atmospheric pressure, this process pushes resins into the moulding cavity.

 

  • Resin Transfer Moulding (RTM)

This process, in closed mould, is ideal for medium volumes and is achieved from clamping resins.

  • Compression Moulding

According to this process, material is fed into an open, heated mould cavity.

 

  • Pultrusion

This is a manufacturing process that features a pulling/ drawing of continuous reinforcements through a resin impregnation system.

 

  • Reinforced Reaction Injection Moulding (RRIM)

This process describes how two or more resins are metered and impingement-mixed, before being forced into a mould and curing.

 

  • Centrifugal Casting

This is a casting technique where molten metal is poured into a preheated die.

 

  • Continuous Lamination

According to this process a combined reinforcement and resin on plastic is pulled through rollers, before curing in an oven.

These processes describe largely automated means of fabricating products and rely on speciality tools and equipment, such as vacuum bags, or temperature-controlled tooling. Often the outcomes are determined by the shape and size of the tool cavity, amongst other variations. Given the tool-specific, capital heavy processing of products, these are often able to produce not only higher volumes of material but appear in larger, more specialist, plant settings.

What is Cast Polymer Moulding?

Commonly, this technique uses Cast Polymer as an umbrella for a style of production that generates synthetic products, usually to meet unique strength requirements. Typically, cast polymers are without fiber reinforcements, but are left to cure inside a mould. This technique might borrow from either closed or open moulding.

Within this branch of composite manufacturing unpacks two main processes, including:

·         Gel Coated Cultured Stone Moulding

As a kind of outer surface, or cosmetic layer, polyester resin is used as means of weather-proofing products for outdoors use.

·         Solid Surface Moulding

Solid surface can produce a variety of cosmetic finishes and is popular for the likes of kitchen design, especially worktops.

What are Prepregs?

Prepregs describe composite materials where a reinforcement fibre is pre-impregnated with thermoplastic or thermoset resin matrix. Cured under higher temperatures and pressures, prepregs often carry through unique properties for application in sectors like rail transport or aircraft manufacturing. Produced through either of two processes, prepregs can be the result of hot melt process or solvent dip process.

Prepregs are advantageous for their many improved properties, including good fatigue resistance, laminate thickness, and improved quality control. But prepregs, through specialist manufacturers, can be engineered to bespoke grades using unique resins for formulations depending on the desired market.

Above: Permali’s 1600 ton press

 

Composite material processing and manufacturing is an expert, if carefully engineered, industry uniquely equipped for advanced applications. Everything from automotive to aerospace, the applications of these composites can be mission critical to how an industry advances and adapts to the pressures of the modern world. Delivering bespoke material solutions, Permali has an industry-leading reputation for manufacturing composites that offer improved protection, better performance, and increased precision.

Whatever your application – get in touch to find out more about our services.