Materials and process guidance for hand lay-up, spray-up and open-molded FRP/GRP fabrication.
Open molding builds a composite on an accessible mold surface. The material system combines a resin matrix, fiberglass reinforcement, surface-layer materials and process-control materials. Start with the finished part requirements, then match the reinforcement, resin and processing method.
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Hand lay-up and spray-up
Hand lay-up: resin and fiberglass reinforcement are placed manually over the prepared mold. Chopped strand mat and woven reinforcement are common material formats to consider.
Spray-up: a chopper gun applies chopped roving and resin to the mold. Select a spray-up roving suitable for the equipment and resin system being evaluated.
Typical production sequence
- Prepare the mold.
- Apply gelcoat where the surface specification requires it.
- Place or spray the resin and reinforcement.
- Consolidate the laminate.
- Allow the specified cure.
- Demold and trim the component.
Choose fiberglass reinforcement by laminate function
| Reinforcement | Selection reference | Typical role |
|---|---|---|
| Chopped strand mat | Brochure range: 80–900 g/m² | Hand lay-up and conformable reinforcement |
| Spray-up roving | E-glass roving for chopper-gun processing | Spray-up molding |
| Woven roving | Examples: 400, 600 and 800 g/m² | Reinforcement and laminate thickness build-up |
| Multiaxial fabrics | Biaxial, triaxial and quadraxial; examples include ±45° and 0/90° | Structural and load-bearing laminates |
| Surface veil | Fiberglass or polyester veil | Surface layers and corrosion-resistant layer systems |
| Glass-fiber fabrics | Plain, twill or satin weave | Thin-wall parts and precision components |
| Stitch-bonded reinforcement | CSM combined with woven roving or multiaxial fabric | Combined reinforcement for lay-up efficiency |
| Continuous strand mat / milled fiberglass | Continuous mat / milled fiber formats | Large-area laminates / bonding and repair pastes |
Weights and constructions are brochure selection references. Confirm the proposed grade, availability and technical data before ordering.
Resin matrix options
- Unsaturated polyester (UPR): general-purpose options include orthophthalic, isophthalic and DCPD systems, with specialist grades for particular requirements. The brochure lists tanks, covers, boats, bathtubs, pipes and structural parts as application examples.
- Vinyl ester (VE): consider appropriate grades when corrosion, heat or hydrolysis resistance is a priority. The brochure includes bisphenol A and novolac epoxy vinyl ester types.
- Epoxy (EP): options for bonding, low-shrinkage and mechanical-performance requirements. Epoxy uses its own compatible curing system.
- Phenolic: grades selected for specified flame-resistance and low-smoke requirements.
- Polyurethane systems: adhesives and special systems for bonding or sandwich construction.
Resin-family descriptions are a starting point for selection, not a guarantee for every grade. Match the actual technical data to the service environment and processing conditions.
Gelcoat and surface-layer materials
Gelcoat provides the exterior finish and protective surface layer and is generally applied before the laminate. Options described in the brochure include standard, tooling, flame-retardant, weather-resistant and clear gelcoats, together with pigment pastes.
Specify whether the application is by spray or brush, the required color and finish, and the relevant exposure or performance criteria. Tooling gelcoats have different selection requirements from finished-part surface coatings.
Supporting materials for the complete system
Cure and reaction-control materials
The brochure groups initiators, promoters, accelerators and inhibitors as materials used to control reaction behavior. Specify the exact resin and compatible cure system when requesting these materials. Cure conditions and any post-cure should follow the applicable supplier documentation; the categories listed here are not a mixing or dosing instruction.
Fillers
Options include calcium carbonate, talc, alumina trihydrate (ATH), silica or quartz powder, mica, wollastonite, feldspar and calcium sulfate. Define the target role—such as viscosity, surface quality, hardness, dimensional control or flame-performance requirements—rather than choosing only by material name.
Structural cores
For sandwich structures, the brochure lists PVC, PET and PU/PUR foams; PP, aluminum and aramid-paper honeycombs; and synthetic mat cores. Include the panel construction, thickness, weight target and process when discussing an option.
Equipment and tools
FRP spraying machines, gelcoat spraying equipment and brushes are included in the brochure. Equipment choice should match the application method and material system.
What to include in your inquiry
- Finished part, service environment and required performance standards
- Hand lay-up or spray-up process, equipment and production conditions
- Reinforcement format, area weight, width, construction and quantity
- Resin, gelcoat, cure-system and core requirements, where relevant
- Current technical data sheets or reference grades for replacement inquiries
- Packaging, destination and required delivery date
Ask for grade-specific technical data, evaluation arrangements, minimum order, availability and delivery terms with the quotation. Confirm material selection against the finished-product requirements, process, cure conditions and applicable standards.