Fibreglass Production Methods
Production Methods
FDL uses a range of open- and closed-moulding processes to manufacture composite components. Each method has different advantages and limitations relating to component size and shape, production volume, surface finish, reinforcement type, resin system and cost. We select the process best suited to the requirements of each project.
Open Moulding
The basic system
Open moulding is a versatile and economical option for prototypes, one-off components and low- to medium-volume production. The component is formed against a single mould surface, producing a finished surface on one side.
Hand Lay-up
Hand lay-up involves placing fibre reinforcement into an open mould and applying catalysed resin manually using brushes and rollers. Chopped strand mat is commonly used, although higher-strength reinforcements can also be incorporated where required.
The process gives the operator direct control over the placement of reinforcement, laminate thickness and resin-to-glass ratio. It is particularly well suited to lower-volume products, complex components and projects requiring variation between individual parts.
Spray-up
Spray-up is another open-moulding process used for low- to medium-volume production. A chopper gun simultaneously deposits chopped glass fibre and catalysed resin into the mould, allowing larger components and complex shapes to be laminated efficiently.
The process is faster than hand lay-up for many applications, although careful operator control and material monitoring are required to maintain the specified laminate thickness and quality. FDL uses flow meters, scales and production controls to monitor material application.
Spray-up is generally most economical for larger components or repeat production. FDL uses open-moulding methods to manufacture products including Breeze Busta truck wind deflectors and a wide range of custom components.
Closed Moulding
Closed-moulding processes use two mould surfaces or a sealed vacuum system to produce components with more tightly controlled dimensions, laminate properties and surface finishes. Tooling is generally more complex and expensive than for open moulding, so these methods are selected where the production volume or product requirements justify the additional investment.
Resin Inject, RTM (Resin Transfer Moulding)
Resin Transfer Moulding is used where a component requires two moulded faces, controlled wall thickness or consistent repeat production.
Dry reinforcement is placed into the lower mould before the upper mould is closed and securely clamped. Catalysed resin is then injected under pressure until it fills the mould cavity and thoroughly wets the reinforcement.
Although the injection pressure is relatively low, it acts across the entire mould surface and creates considerable force. RTM therefore requires strong, accurately manufactured upper and lower moulds. The process can provide good dimensional consistency and efficient production rates, particularly where a pigmented-resin industrial finish is suitable. FDL has used RTM for projects including Post Office sorting trays.
RTM Light
Light RTM uses a lightweight counter mould, reducing tooling costs compared with conventional RTM. Reinforcement is placed into the mould before the counter mould is fitted and sealed around its perimeter using vacuum.
Resin is introduced at low or atmospheric pressure and drawn through the reinforcement by vacuum. Because the laminate is compressed less heavily than in conventional RTM, Light RTM components generally have a slightly higher resin content.
Light RTM can be suitable for repeat production where a closed-moulded finish is required but the pressures and tooling costs associated with conventional RTM are unnecessary. For products that do not specifically require closed moulding, several open moulds may provide a more economical production solution.
Vacuum Processing
Vacuum processes improve laminate consolidation by removing trapped air and controlling the amount of resin within the component. They are commonly used for high-performance components, sandwich panels and laminates requiring a high fibre-to-resin ratio.
Vacuum Bagging
In vacuum bagging, the reinforcement is placed into the mould and wetted with resin by hand, through a wet-out machine or by using pre-impregnated reinforcement.
The laminate is then covered with layers of consumable materials, which may include peel ply, perforated release film, absorbent bleeder cloth, breather material and a sealed vacuum bag. Vacuum is applied while the laminate cures, compressing the reinforcement and drawing out trapped air and excess resin.
The process improves consolidation, reduces voids and can produce a lighter, stronger laminate with a more consistent fibre-to-resin ratio. FDL also uses vacuum bagging to bond cores into composite panels and manufacture high-performance components incorporating materials such as carbon fibre and Kevlar.
Vacuum Infusion
In vacuum infusion, the dry reinforcement is placed into the mould and covered with peel ply, resin-flow media and a sealed vacuum bag. Resin inlet and vacuum lines are positioned within the system before a full vacuum is applied.
The sealed assembly is carefully tested for leaks, as incoming air can cause dry areas or voids within the laminate. Once the system has passed the vacuum test, resin is introduced and drawn through the reinforcement by vacuum.
Vacuum infusion provides thorough and consistent wet-out while producing a strong laminate with controlled resin content and minimal trapped air. It is particularly suited to large or high-performance components and is used by FDL for many aircraft and specialist composite parts.
