What is the hand lay-up process for chopped strand mat (CSTM)?

I. Pre-construction Preparation

 

Material Inspection:

 

Confirm that the chopped strand mat is free of oil stains, damage, and delamination; the fibers are evenly distributed.

Check if the resin type is compatible (commonly unsaturated polyester, epoxy, vinyl ester).

The adhesive is generally a powder or emulsion type; ensure it is not damp and lumpy.

 

Tools and Site:

 

Tools: Roller, brush, scraper, scissors, measuring container, stirring rod.

Site: Well-ventilated; temperature generally controlled between 15 and 30 ℃; humidity ≤ 75%.

Clean the mold surface and apply a release agent to ensure smooth demolding.

 

II. Resin Preparation and Impregnation

 

Resin Proportioning: Add curing agent and accelerator according to the resin manufacturer's instructions and stir evenly.

Pay attention to accurate dosage to avoid excessively fast or slow curing, which would affect the impregnation effect.

Impregnation Operation: Pour the resin onto the felt surface or mold surface and spread it evenly with a roller or brush.

Use a spreading method from the center outwards to avoid air bubble accumulation.

Ultra-thin felt penetrates quickly; the amount of resin applied at one time should not be excessive to prevent dripping and waste, or excessive thickness in certain areas.

 

III. Laying and Compacting

 

Laying Method: Lay the felt layer by layer according to the designed number of layers, ensuring each layer is fully saturated before laying the next.

When laying layers, pay attention to aligning the edges to avoid uneven overlap and thickness fluctuations.

Air Removal and Compacting: Roll the felt from the center outwards to remove air and excess resin.

Use smooth movements and moderate pressure to prevent fiber displacement or tearing of the felt.

Ultra-thin felt easily adheres to curved mold surfaces; the number of rolling passes can be increased appropriately to ensure a good fit.

 

IV. Curing and Post-treatment

 

Curing Conditions: Room temperature curing: Depending on the resin system, this usually takes several hours to a day.

Heat curing: The temperature can be increased according to the resin instructions to accelerate curing and improve performance.

Post-treatment: After curing, demold and check the surface for smoothness, bubbles, and delamination.

If necessary, sand and repair before painting or bonding other parts.

 

V. Precautions

 

Prevent Drying: Prolonged exposure of the felt to air will affect its wettability; use it as needed.

Control Resin Dosage: Ultra-thin felts absorb less resin; excessive resin will result in softer products and greater shrinkage.

Avoid Strong Stretching: Do not pull the felt forcefully during layering to prevent fiber alignment and reduced isotropy.

Safety Protection: Wear gloves, a mask, and goggles to avoid contact between resin and solvents and skin and eyes.