FRP Manufacturing Process: Mold to Finished Shell in 6 Steps

Ever wondered how a custom FRP radome or carbon fiber automotive shell goes from concept to finished product? In this article, we take you through our manufacturing process step by step —from mold preparation to final quality inspection.

Step 1: Design & Mold Fabrication

Every FRP shell starts with a precise 3D model. Our engineering team uses CAD software to design the part, accounting for:

Structural requirements (load cases, impact resistance)
RF transparency (for radomes)
Surface finish requirements
Mounting points and integration features

Once the design is finalized, we fabricate the mold. Depending on production volume, we use:

CNC-Machined Aluminum

High-volume production, excellent surface finish, 10,000+ cycles

FRP Composite Molds

Medium volume, cost-effective, 500-5,000 cycles

Step 2: Surface Preparation

Before layup begins, the mold surface must be meticulously prepared:

Cleaning: Remove all dust, grease, and residue from previous cycles
Release Agent Application: Apply 2-3 coats of mold release wax or PVA film to ensure clean demolding
Gel Coat Application: For parts requiring a smooth, colored exterior, spray gel coat (0.4-0.6mm thickness)

💡 Quality Checkpoint: Gel coat thickness is verified with a wet film thickness gauge. Uneven gel coat leads to surface defects and weak spots.

Step 3: Laminate Layup

This is where the composite structure is built up layer by layer. We use several techniques depending on the application:

Technique	Best For	Fiber Content
Hand Layup	Large parts, low volume	30-40%
Vacuum Bagging	Medium volume, better consistency	45-55%
Resin Infusion (VARTM)	Large complex parts	50-60%
Prepreg + Autoclave	Aerospace, high-performance	60-70%

Typical layup sequence for a sandwich structure radome:

Inner skin: 2 layers of woven fiberglass (0°/90°)
Core: 10mm PET or Nomex honeycomb
Outer skin: 2 layers of woven fiberglass (±45°)
Optional: Surface veil for smooth finish

Step 4: Curing

The resin must cure to achieve full mechanical properties. Curing methods include:

Ambient Cure: Room temperature, 24-48 hours for polyester/vinyl ester
Elevated Temperature: 60-80°C for 2-4 hours, speeds production
Autoclave: 120-180°C under pressure for prepreg systems

Step 5: Demolding & Trimming

Once cured, the part is carefully removed from the mold:

Release air injection or gentle tapping to break the seal
Lift part evenly using spreader clamps to avoid distortion
Trim flash and excess material using CNC router or hand tools
Drill mounting holes and cutouts per drawing specifications

Step 6: Surface Finishing

Depending on customer requirements, we apply various surface treatments:

Paint: PU or epoxy topcoat in customer-specified RAL color
UV-Resistant Coating: Clear coat for outdoor applications
Anti-Static Coating: For equipment enclosures in hazardous environments
EMI Shielding: Nickel or copper spray for RF-sensitive applications

Step 7: Quality Inspection

Every part undergoes rigorous inspection before shipping:

Dimensional Check: CMM or laser scanner verifies critical dimensions

Visual Inspection: Surface defects, gel coat quality, color match

Weight Verification: Confirms laminate thickness and fiber content

RF Testing (Radomes): Insertion loss and boresight error measurement

See Our Factory in Action

Schedule a virtual tour of our 7,000 m² manufacturing facility in Dongguan.

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Conclusion

Manufacturing FRP composite shells is a blend of craftsmanship and precision engineering. Each step —from mold preparation to final inspection —must be executed with care to produce parts that meet demanding specifications.

At Yasheng FRP, we've refined these processes over 10+ years to deliver consistent, high-quality composite shells to customers worldwide. Contact us to discuss your next project.

FRP Manufacturing Process: From Mold to Finished Shell